SR-10 Construction Materials for Coastal Structures by Moffatt and Nichol, Engineers WHO! DOCUMENT COLLECTION SPECIAL REPORT NO. 10 FEBRUARY 1983 distribution unlimited. Prepared for U.S. ARMY, CORPS OF ENGINEERS COASTAL ENGINEERING RESEARCH CENTER s Kingman Building ADD : Fort Belvoir, Va. 22060 Reprint or republication of any of this material shall give appropriate credit to the U.S. Army, Corps of Engineers. U.S. Army Coastal Engineering Researcn Center Kingman Butlding Fort Belvotr, Virgtnta 22060 Contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. AEM MBL/WHO!I 0 0301 00500264 2 A UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) READ INSTRUCTIONS REPORT DOCUMENTATION PAGE BEFORE COMPLETING FORM 1. REPORT NUMBER 2. GOVT ACCESSION NO.) 3. RECIPIENT'S CATALOG NUMBER ; SR-9 4. TITLE (and Subtitle) 5. TYPE OF REPORT & PERIOD COVERED Special Report CONSTRUCTION MATERIALS FOR COASTAL STRUCTURES 6. PERFORMING ORG. REPORT NUMBER DACW72-80-C-006 8. CONTRACT OR GRANT NUMBER(s) 7. AUTHOR(a) Moffatt and Nichol, Engineers 10. PROGRAM ELEMENT, PROJECT, TASK AREA & WORK UNIT NUMBERS 9. PERFORMING ORGANIZATION NAME AND ADDRESS Moffatt and Nichol, Engineers P.O. Box 7707 Long Beach, CA 90807 CONTROLLING OFFICE NAME AND ADDRESS Department of the Army Coastal Engineering Research Center (CEREN-CD) Kingman Building, Fort Belvoir, VA 22060 4. MONITORING AGENCY NAME & ADDRESS(if different from Controlling Office) D31234 12. REPORT DATE January 1983 13. NUMBER OF PAGES 427 1S. SECURITY CLASS. (of thia report) i. UNCLASSIFIED 15a. DECLASSIFICATION/ DOWNGRADING SCHEDULE Approved for public release; distribution unlimited. 16. DISTRIBUTION STATEMENT (of thie Report) 17. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, if different from Report) 18. SUPPLEMENTARY NOTES 19. KEY WORDS (Continue on reverse side if necessary and identify by block number) Asphalts Geotextiles Riprap Coastal engineering Metals Quarrystone armor Concretes Plastics Steels Construction materials Protective coatings Timber ABSTRACT (Contiaue em reverse side if neceaeary and identify by block number) This is a comprehensive report describing design properties of materials used in coastal protective structures and some harbor structures. The mate- rials include stone, earth, concretes, asphalts, grouts, structural and sheet metals, wood, and plastics. The principal physical properties of these mate- rials and their importance in the selection of materials for different types of projects are presented. The materials that have proved most effective and durable in coastal structures, such as stone, concrete, steel, and timber, (continued) DD . anys 1473 EDITION oF 1 Nov 65 1S OBSOLETE UNCLASSIFIED Se SECURITY CLASSIFICATION GF THIS PAGE (When Data Entered) UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE(When Data Entered) are emphasized by detailed coverage of their properties. Synthetic materials used for geotextiles are described in detail also. The report describes the effects of common forces encountered in the coastal environment on the materials' design properties. The effects of material place- ment, joining, and repair methods and of treatments to prolong design life are also presented. The report discusses in detail the impregnation of wood with preservatives and the cathodic protection and coating of metals. Example proj- ects illustrate the use of the materials in breakwaters, jetties, groins, sea- wells, bulkheads, revetments, and harbor piers and wharves. 2 UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE(When Data Entered) PREFACE This report is published to provide coastal engineers with specific guidelines for selecting materials suitable for construction in the marine environment. The study is confined to the properties of these materials and treatments or variations thereof that are applicable to coastal engineering structures. The work was carried out under the U.S. Army Coastal Engineering Research Center's (CERC) Develop Functional and Structural Design Criteria work unit, Coastal Structure Evaluation and Design Program, Coastal Engineer- ing Area of Civil Works Research and Development. The report was prepared by Moffatt and Nichol, Engineers, under CERC Contract No. DACW72-80-C-006. Preparation of the report was under the direc- tion of L.L. Whiteneck, with assistance of L.A. Hockney and S.H. Anderson. Consultation and technical writing was provided by R.J. Barrett, A.L. Roebuck, C.M. Wakeman, W.J. Herron, Jr., and R.A. Morrison and L.J. Lee of Woodward and Clyde Consultants. Cooperation and assistance were provided by Corps of Engineers Divisions and Districts. R.E. Ray was the CERC contract monitor for the report, under the super- vision of Mr. R.A. Jachowski, former Chief of the Coastal Design Branch, and Mr. N. Parker, Chief, Engineering Development Division. Technical Director of CERC was Dr. Robert W. Whalin, P.E. Comments on this publication are invited. Approved for publication in accordance with Public Law 166, 79th Congress, approved 31 July 1945, as supplemented by Public Law 172, 88th Congress, approved 7 November 1963. orn . BISHOP 7 Colonel, Corps of Engineers Commander and Director II IV VI CONTENTS CONVERSION FACTORS, U.S. CUSTOMARY TO METRIC (SI)..... TNTRODUGIDUON Go cmiers ciecsrcteicielercieetelcnele crores cae cterel het meee revelete ne Ibs, (GSMNerEWbG SidipigTINId 656 00:00 00000 000.0.0.00000.0.0000000060 Ze) BACKPLOUNGR rece rete steele eters) share statetnve enetniel cteteretenenetetee Ss, ODJOCELVE voce cs one cence cvetatete ctetcPamel stent ctonenetenel sr eet etenerra 4. Organ¥zation Of REPOT te.) cs wcicctate < wlsloilerol eters. othe avencns MATERIAL REQUIREMENTS FOR COASTAL STRUCTURES.......... Vs (Generale i teow res ececeoecee ee eeoee eee eee eee ee ee oo ew AAS Chergerebageul: a xeyeprealase ooo oob00a0co0 odond0 0000000 > Nonstructural (Propertivesia acre iste citclale rerelevel lel retool . Availability....... eceoeereoeee eee eee ee eee ee ee ee eo 8 . Maintenance and Preservation Requirements........ 3 4 5. Compatibility with other Matenlalisoeie asec. crs cts 6 7 . Environmental Considerations........ccccccecccces eececeerceeerer eee oo eee eee ee ee ee eo 1. Types and General Characteristics of Stone....... . Categories of Stone Size and Gradation........... o SWene Saeewsalenre@nSoo650000000000000000000000000 . Quarrying Methods.. eeceeoe eee eee eee cee eee oe ee ee oe eceere eee ree eee eee oe ee ee ee oe 8 8 5 RE oEbIO Gi? GeO ebEOS 5 bocodoccodgod0dound0Gb000d00S . Environmental Considerations.......cseccecccccres , Uses) in) Coastal Constructione. ccs s secede ier 2 3 4 5. Placement Methods.. 6 7 8 1. Component Types and eceeseeceeeee ec eee ee eo oe 8 ee 8 8 8 8 Glass int Soadisiaiccivcres ctenencrec sere . Properties and Characteristics of Soils.......... . Methods of Soil Improvement..........++seeecees-- . Placement of Soil for Coastal Structures......... . Environmental Considerations.....-.ceccccccccecess 2 3 4 5. Repair of Earth Structures..........ceccccererees 6 7 . Uses of Soils in Coastal Construction............ PORTLAND CEMENT CONCRETE . Introduction....... 5 IbYaOS Ose) [opmreilennel: Camewts5 o09000000000000000500000 Sl PacoyXsipiel Sq ggguaco5 eeeeece eee eee ee eee ee ee ee ee 8 oO ow 8 eeececeee eee eee ner eee eee se ee 8 oO . Preparation of Concrete MixeS..........eeccceeeee . Techniques to Enhance Durability................- . Reinforcing-Prestressing Materials...........+.--- R 1 2 3 4. Components......... 5 6 Ul 8 . Joint Sealing...... 9. Repair of Concrete. eeceereeceo ee eer ee eee eee ee ee ee 8 8 10. Delivery and Placement............++seeeeeeeeeees 11. Environmental Considerations..........-cceceereoe 12> UsSesmain Coastal Structuneseeireieieieistelensntelonenolelele ier OTHER TYPES OF CONCRETE AND GROUT.........-.-------ee> 1. Bituminous Concrete eee ee eee eee eee eo ew ee ew eo ee ew ew 8 8 VII VIII XI NOWMNHWND STRUCTURAL AND SHEET METALS Types and Characteristics of Metals and Alloys... . Joining, Cutting and Repairing Metals............ PEMVERONMeTMEa ly GCONSTAST ATA ONS\.1-lo)ersiclelereloloielsiclelvicterors Ie PLASTICS Generale (PTOPereLes)ecciere aeplelcdeltaloriclsnsisne cere tverorcic GeotextiWleu Ral rensioien. vepcveysrsheusieasycusneueleseusielieieieneitens aie te le 2h RECYCLED AND OTHER MATERIALS TN EBO GU CERO tore. c tesco eno yausrsueieieueie as exeuteue ete seieueieuesd ese susiene se Mal CON CRE CRG fea Merete o cus odio eile js tietassusveaeie ge utis elisiiensierecee ele PAS PN Adie owe petetayoucbonovenerale s Glole cbc te is lobsisketovcrsietovoters waste ¢ ahWNFe SOV PROTECTIVE SYSTEMS FOR MATERIALS PU COMME SHON eis. cPeiiert autem tts uate eke tets Misra i asus otste fel oe is pip COATING SHRP Ris c.c)cr0 elevecusveie wielons ie @ lsueuelape leveqe,duesersuauece siete CachodiicmeRocec trlOmer om ieiecieuirnsuiolee tienersde rine cis . Cathodic Protection and Coatings in Combination.. Marine Atmosphere Features Marine Exposure...... WRWDN EE CONTENTS (Continued) wnneplaced Agpene patel Concrele weit ree) ctels oteteleieie) clei 5 Wopsiele hel (oie (heeiien ga ouuacocoops0oKDCOUOUD SIC eceoeereeer eee ees eee ee eee eee eee eee eee eee eee sees eeeeee se Eh Yy Sue PrOpeNntsesy Of WOO ee ci) atelclcleietcrselelelelerelelolele Mechanical Properties of Wood...............+--6- Sellectvonjof wambery Presi pier. vajsies- ia eret eter ete) siee/ Hee) ene . Characteristics of Common Construction Species... DESCEUCEIVENMBLUO EA o1cteitels ofslete tel epataey = sera tdts cial olavetoreronerene Specific Applications for Treated Wood........... Pe OU NEN CG Mae ear tailis/pepeieetevelel etal svehe) aeieheelevenelcheiovewo) oNekenerore 7) Repair Materials) and Methods nyyeis -selorerels)osereleteton-terel . Environmental Considerations...........e.eeeeeees . Salvaged Ships, Barges, Railroad Cars, Automobile Bodies, Refrigerators, and Others... MRUDDSTIMUN OSH Bie Re re eee Loghe cue TE PeeY To Mae ack tg 5 ceeeereceeoe eee ee ee eee ee ee eo eo we CC ee ee) eocreeece cece eo eee eo ee eo CONTENTS (Continued) Page GewUsescin Coastal yStructunesa ye eee eee eee 372 XII SUMMARY:.0250/ Siotolotaeorele'e clerelotoberetcfetstotoeteects seanmerntaNs, eo Reet TOI cumin teyrs 374 JRL ELS) Si UL ROO DO OO TOOOO LODO DOO OCOD Goo o. 7 OBO Aa OO Ce 374 2. \MAGErTalls MS aae No wciclde a acetate eae OE eee ic 374 3. Some Present Investigations of Coastal Construction Matertall's tas ia is saree atte rete ere) clas 386 PITERATURESGRIED peace ope elrohe) iaisyofel net etepety clone ta telcbenenet de heReneh envoys 396 BIBL TOGRAPRHY. G5 Sei.c, oo) eis rere he cree hee) atonal erode eae 402 APPENDIX A SPECIFICATIONS AND APPLICATIONS FOR STEEL SUITABLE FOR TMARTNE T SERVICE erectile ead irae eee error nn 4.05) B MECHANICAL PROPERTIES OF ROUND WOOD PILES TREATED WITH PRESERVATIVES FOR USE IN SALTWATER..............0..00% 407 C GEOTEXTILESEIETERTTEST St +4225 sae thon ee dee ioe ee cee ela 412 D INFORMAT TONAL” ORGANTZAT DONS: = tecercy.tare aie ails side eeeenene serene ole 416 TABLES Me Glasses) of rocks lope protection: oy scan oie etal ia ioe 32 2. Unified soil classification system (ASTM D-2487)..........-...- 52 3. Improvement of soils for coastal construction.................- 58 4, Characteristics of fill based on nature of borrow material..... 63 Se Chemical limits efonimixangy, watersnce aoe ec a sae cee eerie 74 6.) Permissible: chloride rions ccc nce ois a5 oie ite eae Toes Some teirel eters 75 Wo Typical analyses of city water supplies and seawater 90000090000 76 8. Characteristics and tests of aggregateS..........cccceeeseecees 80 9. Maximum size of aggregate recommended for various types of COMS ELHUCETOM a alors oiayiere ote cl cvereseie tian cr enor eire bat cl oitontontal on etcornettetrenemts tetas ToctAviny erefie 81 10. Recommended slumps for various types of construction........... 95 11. Approximate mixing water requirements for different ‘slumps and” sizes of jagoregatesy i244 6 teh kc ie ut ee mei eee einer a eutere 97 12. Relationships between water-cement ratio and compressive Strengeheobycomcretec nitric wee cere ei oti etteite ire iol ectncrers 98 13. Maximum permissible water-cement ratios HES air-entrained CONCTELE MIN SeVETEMEXPOSULe sicretrei rete ieieiichale rotenone hentai tener 98 14. Volume of dry-rodded coarse aggregate per unit of volume of COINEWSEO.s 06.006000000000000000000000000n0000000000000000000000 100 IS) a Eirst estimate Of wel phitsot freshCOncCre terrence ieletiernnderietcens 100 16. Techniques to obtain maximum durability................--+ee00> 113 Wis Serene Cie Swell WaesSeoanoconccscgdn00c Dd oKCGCDDGOOCOOOOOONNC 116 18. Approximate yield point and proportional limit................. 116 19. Secant modulus at proportional limit.........+.-seeeeereeeeeeee 20. Materials used for sealants in joints open on at least one SIAC Cee ss 90 GOO ODDO OGDOD0bVD ODO DD ADO DOS A4ODO UI ODIM UCONN" 21. Preformed materials for waterstops, gaskets, and sealing purposes. FHI OLS AON OS. OAH LC. how ce Oh Bere ieiata mane bier Jojp,, SERENE CHE comnon ly wsedechemicalis’ on) CONCTELE. sams «esi eee 25). Ly picaleconernete armor unitseiniusey today/-jerm-llsee -leleiss= “ets 24. Concrete armor projects in the United States........ SdogeaaceDo 25. Applications of asphaltic materials for hydraulic structures... 26. Typical aggregate gradations for preplaced aggregate concrete prepared with fine sand grout nae pozzolan and PMU ATE ME RR fetalohs teks otek toe ts fore tore oreclore eels odele eke treks tere mpe trict ca ole eieiers 27. Classification of coppers and copper “alloys d90a00500000dN000000 28. Galvanic series in flowing seawater at ambient temperature..... 29. Friction piles - specified tip circumferences with minimum DIUGEMCAMCUMPENENCESH mucter terse eicveiele oleh clotenereccuoteteMp fic otelene otis lebere ones 30. End-bearing piles - specified tip circumferences with minimum HUeCCINCUMPETENCE See iret tiaieer. ota etetetotereleipheloielledeteve teverohetete 37. Construction limitations: quarrystone revetment..............-. 38. Construction limitations: block revetments and subaqueous applications..... So0000 ooudcecoc dob uooocnuoDcoadocolooOOCoUud 39. Minimum geotextile filter physical property requirements....... 4025 Corrosion’ rate or somescommon metals. . 2. .<..-scieeeae as sme eeeae. 41. Types of coatings commonly used on different substrates........ AG. (GOEKETINE COUTIMEIMER ooccccoGacooucdsodaodUGD DOGO HKOddOUCoOUKGOK 452" Recommended scoatingrsysitemsinc itt cise cleiels aie ene clisisin - i olor 44. .Qualities of various coatings.......... C22e erieere kode: ce tcr 45. Residues permitted to remain on blast cleaned surfaces......... 46. Recommended surface preparation for specified coatings......... 47. Types, sizes and resulting profile of abrasives used in air DAS SoWabuieMeocoopoopsound oN Co oDb UDO Ob ODD UNOODOUOD GOD DDDN OD 432 sand: and ai rElows CONSUMP EDOM. ca0agg00d0000000000000000000000 Sketch of typical damaged pile and fiberglass form.............. Piles repaired using fiberglass forms and grout................-. Wood bearing piles with P.V.C. wrapping...........seccececseeees PaWolGc Macehayererl joulile: trae icobe Giahyebnus oo ococoobOoGUd0Gb0000000000 Beach protection with "billboard" groins, Ninilchik Harbor, IMMASIELo Gooo odo oGoo dob bo obo Goa OO DDDOOOOODOOODOdDpODOODDDDO DOORS MASI, oosab cone cog OCF DOD OD DODO DODO ODDDOOO HOC DO0DD000RDCDDON0NE iwommethods oremaki noe bas cine RMaGeneSSeS oreo aterelelel alee -lellalos-lahel ele) kel« Submerged current control screen made of "wattles''.............. Examples of wood-formed Cribs. 32.2.2... 0. cece ewer eres essere Sand fence using brush for filter material..............ccceeee- Geotextaudliel staliterns) mere ve CMe;ntS)ycejerelonelepel clo enelel elelenel tele te elelianeleleltolell= Two types of double layer fabric forms.............0222-eeeeeees Double-layer fabric forms being installed...............--++e-eeee Longard tubes being filled with sand for beach nourishment DUOWSSEs ocoooodoovooagno ob aHoadgoDUDOGDD OKI OOD ODOD DD COC ODDDOODN Concrete filled bags of synthetic fiber used for shore DOESSEMOMs ococcsgodgaondenobooo oC dd ODODDD DN OODDOUDOAODOOOUGORD Oil containment boom made of synthetics..............0220002000- Typical uses of molded high density polyethelene................ FIGURES (Continued) Page sea cushion! with) Girenchainmne terns «cirieicielrertereae o cperaickerieieiciorke 305 EorrosTON PLOCESSirev-ter-rkerstoreteroreeteierens let kepete there tebe te Neken tarsi eseletekel sero 319 Corrosion) process: an pilpelamesims selceielicictoierere) levee cele ielotelanevelersis 320 Examples of design details to aid coating application........... 323 "Palmed'' application of epoxy underwater coating...............-. 329 E€rosseditlinked vepoxy.phenolaicaa darecior teenies srateloie le = eleyelteusisncleienscene) oie 330 Surfacerblastaing spro Files a5 9 ecw cele sin clei cielo serene otcnensnekocneiteieuenosers soil 336 Diagram of simple impressed current cathodic protection......... 350 Copper sulfate electrode test Circuit............--ccecccccccees 354 Potentials related to time on interruption of cathodic PFOtectionecurrentls.5 5.5 terriers Meee memercme er elele -ciekenmetelcieicieys 359 Circuit fortoff potential emeasurementhenn. socewes + occ cer 360 ; Anode’ n= carbonaceousi back£al . 25 Fahrenheit) is reached; at this point the decomposition of the stone begins, due to the driving out of carbon dioxide. The stone then tends to crumble, because of the flaking of the quicklime formed. Marble, due to the coarseness of the texture and the purity of the material, suffers more than limestone. The cracking is irregular, and the surface spalls off similar to that experienced by granites. Sandstones, especially if of a dense, nonporous structure, suffer from high temperature and sudden cooling less than most other stones. The cracking of sandstones that does occur appears mostly in the planes of the laminations. Sandstones in which the cementing ingredient is silica or lime carbonate are better fire resistants than those in which the grains are bound by iron oxide or clay. 8. Uses In Coastal Construction. a. Offshore Structures. (1) Breakwaters. Stone is one of the principal materials used in breakwater building. It is used from the core to the armor in various lifts and layers each having a different gradation. Not all cores are made of stone but when a stone core is used it usually is made of impermeable quarry run stone. The core is covered by a blanket of filter material graded to protect the core from eroding away due to the action of waves and currents and to allow changes of hydrostatic pressure in the core without loss of core material. The next layer is usually the underlayer graded to be stable against the anticipated surge and current action. The final layer of armor stone is placed in the area where waves impinge on the breakwater. Armor stone is graded and sized to remain stable under the impact of unbroken, breaking, and broken waves. Where storm waves may overtop the breakwater, armor stone must be placed on the backslope as well as the seaward face. The elevations and width of crest will depend on the desired use as well as the degree of porosity. Porosity or void ratio is important in dispersing the wave energy and reducing the impact load of the waves striking the breakwaters. The design size of armor rock for a breakwater is a function of slope, density, and wave height (U.S. Army, Corps of Engineers, 197la). Hence, the primary concern in the selection of armor stone is density, durability, and available size. Armor stone may be required in pieces varying from about 9 to 270 kilonewtons (1 to 30 short tons). It is usually difficult to quarry, transport, and place stones larger than 270 kilonewtons in size. 46 Therefore, as design wave heights increase, it becomes more economical to use the more efficient concrete shaped structures such as tetrapods, tribars, and dolos (see Section V). (2) Fill Material for Caissons. Due to its density and generally low cost, stone fill material is frequently used to ballast caissons and sheet-pile cells. Rockfill should be well graded and free of loam and organic material in order to have the highest density and minimize settle- ment or, in the case of a perforated caisson, minimize the loss of material due to currents or wave action. (3) Toe Protection. One of the major causes of failure, or struc- tural damage, of breakwaters has been the undercutting of the toe of the structures. When waves impinge on these structures, they not only exert large impact forces on the armor stone, or face of a vertical structure, but they may also impose strong uplift forces on the lower armor stone and toe stone. Thus, the armor stone must be carried to sufficient depths to resist these forces. An additional problem is the turbulence created in these depths, particularly in the case of waves breaking directly on the structure. This can create scour of the sandy bottom and result in under- mining the toe stone resulting in general collapse of the armor layer and exposure of the smaller stone of the underlayers. This can be controlled either by carrying the armor and bedding layers to sufficient depth or the toe section can be overbuilt in anticipation of the quarrystone settling into scour holes. The design of such toe protection is dependent upon wave height and relative depths of the toe protection as compared to the depth of the natural bottom (U.S. Army, Corps of Engineers, CERC, 1977). The same care must be taken as in the design of the rubble structure. b. Shore-Connected Structures. (1) Breakwaters, Jetties, and Groins. (a) General. The primary difference between a breakwater and a jetty or a groin is that the jetty or groin must have a sand-tight core in order to prevent the passage of littoral materials or currents through the structure, whereas breakwaters may be designed to be either permeable or impermeable. All these structures may be subjected to very large breaking or nonbreaking waves. Overtopping of breakwaters and groins in the breaker or uprush zone may be acceptable, but overtopping of jetties must be restricted to prevent passage of sand into navigation channels. Breakwaters connected to shore would otherwise be designed to use stone in the same manner as offshore breakwaters. (b) Jetties. Jetties are usually constructed from the shore- line through the breaker zone seaward to 12- to 18-meter (40 to 60 foot) depths. They are generally perpendicular to the shoreline. However, due to perhaps as much as a 30 skew, or because of variable wave directions, their alinement may vary from 0 to 90 from the direction of wave travel. Because of variable depths, different parts of the structure may be exposed to unbroken, breaking, or broken waves. Thus with careful design, the elevation, total cross section, and size of armor rock can be varied to produce an economical structure. As jetties are used to define harbor or river access to the sea they may be subjected to major tidal or river 47 currents or a combination of tidal and river flow. This must be carefully considered, particulary in design of the inner toe of the structure. As the jetties' primary purpose is to prevent the passage of littoral material through the littoral drift zone, the uprush area must be impermeable or sand tight. Other design considerations are much the same as for a break- water. (c) Groins. The structural design and the selection of stone sizes and gradation for a groin are much the same as for a jetty. The primary difference is that whereas in a jetty, no sand should pass through or over the structure, most groins are part of a beach stabilization program and it is usually desirable to permit some littoral sand to pass around, over, or through the groin. This is not to imply that the permea- bility of armor stone can be designed to allow a selected amount of sand to bypass, since current design procedures are not capable of designing successful functioning permeable groins. Many attempts have been made to design groins with a varying degree of permeability. For rubble-stone groins, it is usually adequate to design the elevation of the impermeable core through the nearshore and foreshore area to the desired beach profile. The voids in the armor rock will generally be adequate to pass the surplus sand through to the downdrift beach. Groins usually terminate just seaward of the breaker zone in from 1.8 to 3.6 meters (6 to 12 feet) of water (MLW), and the seaward end is designed against the largest breaking wave possible at that depth, taking tidal elevations into account. The breaker zone is an area of constant turbulence and care must be taken to properly place, as well design, the bedding layer or the structure will fail. Considerable success has been experienced in recent years in replacing this bedding layer of stone (or combining it) with filter cloth. (2) Seawall or Revetment. A stone rubble seawall or revetment is used to protect the shore, or a shore structure, against erosion by wave action or currents (Fig. 7). It may be a trapezoidal gravity seawall-type structure, backfilled by shore material, or it may be a form of sloped revetment against a shore bank of earth, wood, steel, or concrete. (a) Current Protection. A revetment designed to protect against currents, tidal or river, is designed much the same as a river revetment except that, in the case of tidal currents, the flow may be reversible. When river and tidal currents combine, tidal elevations must be considered to determine the stage of maximum or critical velocities. Also in bays or large river mouths, consideration must be given to local wind waves, residual swell, or seiching from the open sea. In the case of river mouth entrances, the revetment may simply represent a transition section from the steady flow river revetment to the wave exposed jetty. In other cases, where a jettied entrance connects the open sea to a bay or wide mouth and the channel is of such width as to create currents, the shoreline facing the channel must be revetted. In the same manner as for a breakwater, there must be a layer of armor rock, an underlayer, and a filter layer. Special consideration should be given to ensure stability of the toe of the structure because of the unidirectional flow of most currents. (b) Wave Protection. The design of a rock rubble face of a seawall or revetment against wave forces is similar to that of the seaward 48 eee pie ae = Figure 7. Stone rubble revetment at Jacksonville Beach, Florida. face of the breakwater. The armor stone must be designed against the force of breaking waves, nonbroken waves, or broken waves. The design size of armor stone will be a function of density, slope, and wave height. In contrast to some breakwaters, almost all seawalls or revetments must be designed to an elevation to prevent wave overtopping. Care must also be taken to construct an adequate toe structure to prevent undermining of the structure during severe wave action. This may not be a serious problem in lakes or bays where advantage can be taken of prolonged periods of small or no wave action to construct the toe trench. Conversely, along the open seacoast, where the action of the surf is continuous, it is generally not possible to excavate to a sufficient depth to reduce scouring velocities. The usual alternative is to overbuild the toe structure in the anticipation that as sand is scoured from under the toe, the excess rock will drop into place and maintain toe support of the structure. Fixed structures generally have smooth and vertical, or near vertical, faces on the seaward side. The effects of turbulence due to wave action or scouring velocities due to currents can be stronger and more serious on these structures than on rubble structures. In these cases the toe struc- ture can serve two functions: (1) Designed as a submerged rubble structure, it may rise an appreciable height above the natural bottom and serve to reduce wave or current stresses on the fixed or solid structure (U.S. Army, Corps of Engineers, CERC, 1977); or 49 (2) designed as a filter blanket or bedding layer, it may be used to prevent scouring of the natural bottom material which might result in undercutting of the wall. (3) Piers and Wharves. Revetments at pier abutments must be protected the same as any open revetment and in addition must be designed to protect the abutment from loss of foundation. Piers in sandy areas are subject to scour around pilings where strong currents also exist. They can be protected by laying down a quarrystone blanket under the pier in the scour area. c. Anchors. Deadweight anchors can be any object that is dense, heavy, and resistant to deterioration in water. The type of ocean opera- tion and the availability of materials usually dictate the shape, form, size, and weight of a deadweight anchor. Common examples include stones, concrete blocks, individual chain links, sections of chain links, and railroad wheels. In most instances, a deadweight anchor functions simply as a deadweight on the sea floor that resists uplift by its own weight in water and resists lateral displacement by its drag coefficient with the sea floor. The use of stone as deadweight anchors becomes increasingly im- practical as the holding capacity requirement exceeds 6.7 kilonewtons (1 500 pounds). 50 TV. EARTH 1. Component Types and Class of Soils. Under the words "earth" or "soil,'"' a large assortment of materials of various origins is covered; for engineering purposes these are generally classified as gravel, sand, silt, clay, and organic material. Most soils are composed of a mixture containing two or more of these materials. Different geological processes (such as alluvial, residual, glacial, or loesial), and parent materials (sedimentary, igneous, and metamorphic) will affect the type and nature of the soils formed. A soil can be de- scribed by its grain-size classification, appearance and structure, and compactness or hardness. There are several soil classification systems, but the most widely used in engineering is the Unified Soil Classification System (USCS). The USCS is presented in the ASTM Standard D2487 and MIL-STD-619A. A summary of the classification system is presented in Table 2 and the general soil characteristics are discussed in the following paragraphs. Table 2-3 in TM S-818-1 is another useful version of USCS. A more detailed presentation of the classification systems and soil properties can be found in the report entitled "Geotechnical Engineering in the Coastal Zone," Callender and Eckert (in preparation, 1983). a. Coarse-Grained Materials. Gravels and sands are known as coarse- grained soils. Coarse-grained materials are such that 50 percent or more of the materials by weight are retained on the No. 200 sieve. They are recognized either visually and manually or by means of the following parameters: - Effective grain size (Dig): grain size such that 10 percent by weight of the materials are finer. Deo - Uniformity coefficient (C) Sines 2 (D30) - Coefficient of curvature (C) = Dio - Deo Because most soils are composed of more than one type of constituent, the USCS makes the following distinctions for sands and gravels: - Well-graded gravel (GW) or sand (SW): all particle sizes are represented within the constituent limits, C_ is greater than 4 or 6, respectively, C_ is between 1 and 3 and the fraction smaller than the No. 200 sieve size does not exceed 5 percent. - Poorly graded gravel (GP) or sand (SP): some particle sizes are missing or are in excess within the constituent limits, gradation requirements for (GW) or (SW) are not met, and the fraction smaller than the No. 200 sieve size does not exceed 5 percent. S| Table 2. Unified soil classification system (ASTM D-2487). Group Major Divisions ymbols Typical Names Laboratory Classification Criteria Deo (Dan)* Cy = — greater than 4, Co = ———__ between 1 a0 3 | Dio Din « Dow Well-graded gravels, gravel-sand mix- tures, little or no fines Poorly graded gravels, gravel-sand mix- tures, ttle or no fines Not meeting all gradation requirements for GI Clean gravels (Little or no fines) Atterberg limits below “A”! panove “A tine with PI, Silty gravels, gravel-sand-silt mixtures 9 9 tine or PI. tess than 4 between 4 and 7 are border- line cases requiring use of Atterberg limits below “A” | gual symbols fine with P.J. greater than 7 larger than No. 4 sieve size) of fines) Clayey gravels, gravel-sand-clay mx- tures (More than hall of coarse fraction is Borderline cases requiring dual symbols” Gravels with fines (Appreciable amount GW, GP, SW, SP GM, GC, SM, SC Deo (D3o)* Cy = — greater than 6; C. = -—————_ hetween 1 and 3 Dro Dio * Doo Well-graded sands, gravelly sands, little or no fines Coarse-grained soils (More than half of material is larger than No. 200 sieve size) Poorly graded sands, gravelly sands, littie or no fines Not meeting all gradation requirements for SW Clean sands (Little or no fines) Atterberg limits above “A” Silty sands, sand-silt mixtures fine or Pt. less than 4 Limits plotting im hatched zone with Pt. between 4 and 7 are borderline cases requiring use of dual sym- | bols Clayey sands, sand-clay mixtures Auterberg limits above “A” line with P.I. greater than 7 smaller than No. 4 sieve size) of fines) = < ° 3 2 = e = s ° ° x) 3a £ c s = & i=] 2 Sands with fines Less than 5 per cent More than 12 per cent 5 to 12 per cent (Appreciable amount Depending on percentage of fines (fraction smaller than No. 200 sieve size), coarse-grained Oetermine percentages of sand and gravel from grain-size curve. souls are classified as follows: Inorganic silts and very fine sands, rock flour, silty or clayey fine sands, or clayey silts with slight plasticity Plasticity Chart Inorganic clays of tow to medium Plasticity, gravelly clays, sandy clays,. silty clays, lean clays Organic silts and organic silty clays of low plasticity Silts and clays (Liquid limit less than 50) Inorganic silts, micaceous or diatoma- ceous fine sandy or silty soils, elastic silts CEUs CH Inorganic clays of high plasticity, fat CL clays CL-ML Organic clays of medium to high mae MS Plasticity, organic silts 0 10 = 30 30 50 60 70 80 90 100 Liquid limit Fine-grained soils (More than half material is smaller than No. 200 sieve) Plasticity index Silts and clays (Liquid limit greater than 50) Peat and other highly organic soils ° Division of GM and SM groups into subdivisions of d andu are for roads ond airfields only. Subdivisionis based on Atterberg limits > suffix d used when L.L.is 28 or less andthe Pl. is 6 or less; the suffix u used “when L.L.1s greaser than 28, Borderline classifications, used for soils possessing characteristics of two qroups, are designated by combinations of group symbols. For example! GW-GC, well-graded gravel-sand mixture with clay binder. 32 - Silty gravel (GM) or sand (SM): more than 12 percent by weight are finer than No. 200 sieve, and the fines have little or no plasticity. - Clayey gravel (GC) or sand (SC): more than 12 percent by weight are finer than the No. 200 sieve, and the fines are plastic. When the fraction smaller than the No. 200 sieve size is greater than 5 percent and less than 12 percent, a dual symbol should be used. Well and poorly graded gravels and sands are further defined as clean gravels or sands; silty or clayey gravels and sands may be referred to as dirty gravels or sands. It should also be noted that the particle shape has an influence on the density and the stability of the coarse-grained soils. (1) Gravel (G). The USCS defines gravel as the material whose size ranges between 76.2 millimeters (3 inches) and the No. 4 Sieve. Materials larger than 76.2 millimeters are designated as cobbles. Gravels may be man-made (crushed stone) or may come from natural deposits (bank- run). Gravels are cohesionless materials. (2) Sand (S). A material is defined as sand when its grain size is between 4.76 and 0.075 millimeter (No. 4 and 200 sieves, respectively). The USCS developed further classification: the sand is coarse when its grain size varies between 4.76 and 2.00 millimeters (No. 4 and 10 sieves, respectively); medium when between 2.00 and 0.42 millimeter (No. 10 and 40 sieves, respectively); and fine when between 0.42 and 0.075 millimeter (No. 40 and 200 sieves, respectively). Sands are cohesionless materials, however, they present an apparent cohesion when damp or moist due to surface tension effects of pore fluids. These effects disappear when the sand is saturated. b. Fine-Grained Materials. Silts and clays are known as fine-grained soils. Fine-grained materials are such that 50 percent or more of the materials by weight pass the No. 200 sieve. They are distinguished either visually and manually or by means of the Atterberg limits. The USCS, contrary to most other classification systems, does not make any size distinction between silt and clay. This is because the engineering proper- ties of fine-grained soil are more closely related to plasticity character- istics than to grain size. The USCS distinguishes the following: - Silt, clay, and organic silt and clay having liquid limits less than 50: ML, CL, and OL, respectively. - Silt, clay, and organic silt and clay having liquid limits greater than 50: MH, CH, and OH, respectively. Fine-grained soils usually have a low permeability (GUO elo) Oe centimeter per second) with silty soils being somewhat more permeable than clayey ones. Organic materials tend to lower the strength characteristics of the soil, lower the maximum density, increase the time for consolidation and increase the optimum water content. 53 (1) Silt (M). Silt is a fine-grained soil of low plasticity which may exhibit an apparent cohesion due to capillary forces. Silts have relatively poor strength characteristics, except when they are dry or in the form of siltstones and are poor foundation materials in cold climates due to frost heave. Confined, relatively dense silts may perform satis- factorily as foundation soil, but must be evaluated on a case by case basis. Most coastal silts are found in combination with some clay which will increase cohesion and improve foundation characteristics. (2) Clay (C). Clay is distinguished by its fine particle size and cohesive strength which is inversely related to its water content. For this reason, a clay's performance as a foundation material is strongly influenced by its stress history. In situ overconsolidated clays, clays which have been loaded to higher stresses than the present load may per- form quite well in foundations. Normally consolidated or underconsolidated clays typical of estuaries will generally experience large settlements when loaded. The minerals included in the clay composition influence the properties of the soil; e.g., montmorillonite is a highly active mineral, and a soil containing such a mineral will present high swelling and shrink- age characteristics. Two other commonly occurring minerals are illite (less active than montmorillonite and commonly found in marine clays) and kaolinite (the least active mineral). c. Organic Materials (OQ). Peat, organic mulch, and muskeg are highly organic soils which usually have a spongy nature and a fibrous texture. Organic materials come from the decay of vegetable matter. They are recognized by their odor, which is intensified by heating, and by their dark color (although some dark soils may be inorganic). Usually organic soils have high moisture and gas contents and a relatively low specific gravity. 2. Properties and Characteristics of Soils. The major significant engineering properties of soil are shear strength, compressibility, and permeability. The types of geotechnical problems encountered in the design of coastal structures which utilize these charac- teristics are slope stability, bearing capacity, settlement and erosion. A detailed discussion of the properties and characteristics of soils and the tests required to determine them can be found in Geotechnical Engineering in the Coastal Zone (Callender and Eckert, in preparation, 1983). The potential contaminants derived from industrial wastes, such as toxic heavy metals (mercury, cadmium, lead, and arsenic), chlorinated organic chemicals (DDT and PCB's) and pathogens (bacteria, viruses, and parasites) should also be considered in the evaluation of the use of any soil in coastal structures. In general "polluted" soils should not be used. a. Shear Strength. The three types of tests commonly performed to determine soil strength are designated as (1) Unconsolidated-Undrained triaxial test, commonly known as a UU-Test or Q-Test, (2) Consolidated-Undrained triaxial test, commonly known as a CU-Test or R-Test, and 54 (3) Consolidated-Drained triaxial test, commonly known as a CD-Test or S-Test. The Q, R, and S designations are standard use in Corps literature. The descriptions are indicative of the conditions under which the tests are run. From the results of these tests the stress-strain characteristics are estab- lished under the various loading conditions noted, and of equal importance, the conditions of failure for the soil are established. The strength of a soil is usually defined in terms of the stress developed at the peak of the stress-strain curve and is presented in the form of Mohr circles and a Mohr failure envelope. The strength is then expressed in terms of cohesion and the angle of internal friction. b. Compressibility. The simplest compressibility or consolidation test is the one-dimensional, laterally confined compression test (often referred to as oedometer test). In this test the soil sample is placed within a restraining ring and loaded with special types of plates on either top or bottom or both. The change in sample height is measured by a deflection gage and is used to calculate the change in void ratio (e) at different normal pressures (P). If the soil is saturated, the sample is placed between two porous disks that permit the water to drain away during com- pression. This in turn leads to information which permits plotting of the so-called e-log P relationship. From such plots for either sands, silts or clays, or mixtures of them, normally moduli are estimated which can then be used for consolidation and settlement estimates. It should be emphasized that in such tests the lateral expansion is restrained. In real situations this is only approximated by the loading of relatively thin layers of com- pressible soil through load distribution over a large area. (1) Compressibility of Sands. The most important property of the sand, which governs the stiffness of the sand, is relative density. The relative density of the sand is usually determined in the field by means of standard penetration tests or Dutch cone penetration tests. (2) Compressibility of Clays and Silts. The predictions of static settlement of silts and clays are usually made on the basis of consolidation or oedometer tests. The rate of settlement and the time for essential com- pletion of primary consolidation can be predicted on the basis of this test. Typically, silts are less compressible than clays. c. Permeability. Permeability is the soil property that indicates the relative ease with which a fluid will flow through the soil. The coefficient of permeability (k) of a soil is defined as the average percolation velocity (v) divided by the hydraulic gradient (i) in the soil at that particular point. It is seen then that the coefficient of permeability has units of velocity, commonly centimeter per second or foot per minute. Permeability depends on the characteristics of both the pore fluid and the soil. Viscos- ity, unit weight, and polarity are the major pore fluid characteristics. Particle size, void ratio, composition, fabric, and degree of saturation are the major soil characteristics. In general a qualitative approximation of the permeability of the materials can be made on the basis of grain size. For example, clean gravels will have permeabilities ranging from 1O°S Eo 10*? centimeters per second. Clean medium to coarse sands will have perme- abilities ranging from 10-2 to 1 centimeter per second. Very fine sand 55 *(Aueduo) yireg pedstozutoy ayy, Fo ASoqInod 0j0Yd) BYSeLY ‘3anqsieieg 3B UOTIJONASUOD [[eMeaS YIIeO padTOFUTOY °9 oansTy 56 will have permeabilities ranging from 107° to 10°* centimeters per second. Organic and inorganic silts, mixtures of sand, silt and clay, glacial till, and some stratified clay deposits will have permeabilities ranging from NOm? to 107° centimeters per second. Clays, which are practically impervious and commonly used for core materials in water-retaining embankments, will have permeabilities ranging from 10-2 to 10°’ centimeters per second. d. Other Properties and Characteristics. Other soil properties and characteristics that are useful to know for the design of coastal structures include dry density, water content, specific gravity, resistivity and corrosion potential, grain-size distribution, plasticity characteristics, chemical properties, and durability. 3. Methods of Soil Improvement. Methods of soil improvement generally include densification, drainage, changing soil properties at depth by grouting or injection, surface sta- bilization by admixtures, and reinforcement with metal or fabric strips or mesh. Most of these methods have been utilized in one manner or another to improve soils used in the construction of coastal structures. The most widely used, and generally the most practical, are densification and drain- age. A somewhat newer method developed in Europe, and now being more widely used in the United States is reinforced earth (Figs. 8 and 9). Some of the methods available for improvement of soils are classified according to the basis of soil improvement, as shown in Table 3 (Mitchell, 1976). REINFORCED VOLUME TETRAPODS, 4.2YD3 _EL-27.5_ REINFORCED VOLUME DRAINAGE LEVELING PAD BLANKET ROCKFILL, 0.1-0.5T RIP RAP, 0.5-1.0T Figure 9. Cross section of reinforced earth seawall at LaReunion Island in the Indian Ocean (courtesy of The Reinforced Earth Company) . 57 Ajyuazostun AR Twr0F Tefszeqeu TITFAIeqQ ‘s[TTos pezeinjzes -Tun poob ‘set soutjy 30d oz ueyy Jo uot joeduo0s. 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Placement of Soil for Coastal Structures. Earthfills for coastal developments can be placed from the land by dumping or shoving into place, from water by deck and bottom-dump barges, or hydraulically from dredging operations. The method and equipment used depends on the type and source of material, the area of placement (above or below the water level), the depth of water (for operating bottom-dump barges), the purpose and design of the structure or fill, the availability of equipment, the impact on the environment, and the economics of the operation. The material may also be placed with or without compaction to alice ehessoulaidensastys a. Dumped Loose Fills. Soils obtained from land sources are typically transported by and dumped from trucks, scrapers, conveyor belts, or possibly shovels. The materials are then shoved into place and leveled. Soils obtained from marine sources are typically excavated by shovels, draglines or bucket-dredge, and either dumped directly in place or placed in trucks or barges and transported to the site. The soils placed in trucks would be dumped the same as a landfill. Soils placed in barges would be transferred to shore equipment or dumped through the water (Fig. 10). Soils placed in this latter manner will typically have low to medium relative densities. The placement of fill landward of a bulkhead driven into a mud bottom may result in the formation of mud waves. Such mud waves can progress Figure 10. Fill being placed by tilt barge at Redondo Beach, California (photo courtesy of Woodward-Clyde Consultants). 6l ahead of the advancing fill and overload the bulkhead causing its failure before the landfill reaches it. The mud should be removed before fill placement or the bulkhead designed for the increased pressures of the mud wave. Care should also be taken to place select fill behind the bulkhead before placing the general fill to ensure that the active pressure zone has the shear strength planned in the design. Excessive turbulence in dumping fill material through water should be avoided in order to prevent segregation of the materials or extremely flat slopes at the edge of a fill. Uncontrolled bottom dumping from barges through great depths of water will encourage segregation and spread fill over a wide area. Berms or dikes of coarse-grained material or stone can be used to confine the material. b. Compacted Fills. Where compaction of fills above the water level is desired, either the method of compaction or the desired compaction can be specified. A test section is usually required to determine the effective- ness of the methods before specifying a particular method. Otherwise, the required density, moisture limits, and lift thickness are specified, allow- ing the contractor some selection in compaction methods. Coarse-grained, cohesionless soils with less than 4 percent passing a No. 200 sieve for well-graded soils, or with less than 8 percent for uniform gradation, are generally insensitive to compaction moisture. These soils should be placed at the highest practical moisture content and compacted by vibratory methods. Where materials with sizes up to 150 millimeters (6 inches) maximum are used, the large sizes will interfere with the compaction of soil smaller than a No. 4 sieve or 19-millimeter (0.75 inch) size. Where large parts (more than 30 percent by weight) of gravel and cobbles are present, a slight reduction (several percent) in the required density of the sizes smaller than a No. 4 sieve may be tolerated. ce. Hydraulic Fills. Hydraulic fills are placed on land or under water by pumping material through a pipeline or by water sluicing through a con- veyor. Borrow materials used for these fills are generally obtained by dredging (Fig. 11). The characteristics of such hydraulic fills may be generally classified according to the nature of the borrow material (Whitman, 1970). This classification is shown in Table 4. Generally, material with more than 15-percent nonplastic fines or 10- percent plastic fines passing a No. 200 sieve should not be placed under water. The wash water for hydraulically placed fills on land should run off in such a manner that fines are not concentrated in pockets. This may require advancing the fill from one side or corner of the area, attempting to force out any soft fines ahead of the fill as it is placed. Hydraulic fills placed behind walls or bulkheads should be placed in lifts thin enough to permit runoff of wash water without building up a full height of hydrostatic pressure. Dredging and handling operations will produce significant textural differences between original bottom sediments and sediments deposited at the fill site. In general, these differences are an increase in the mean grain size as fines are lost and a decrease in the uniformity coefficient (see Table 2) of delivered versus bottom sands. The volumetric losses 62 resulting from winnowing associated . with this process appear to be on the order of 10 percent or more, depending on the original bottom material. d. Artificial Beach Restoration. The placement of sandfill along a part of shore front for beach restoration may be done in three ways. It may be placed directly onto the shore to be protected or developed as a beach; it may be placed in an area adjacent to and updrift of the area to be protected; or it may be placed offshore. That LS) dteemay be dinectly, placed, placed to form a feeder beach (designed to be eroded by waves and tidal currents and transported via longshore transport to the area to be protected), or placed as a bar (designed to be transported inshore by waves and currents). To be effective, offshore restoration must involve placing fill in the zone where shoreward movement of the sand occurs, piling it as high as possible, and placing it during the spring or early summer to take full advantage of the seasonal beach Figure 11. Dredge Chequinquira building before the annual period of at dock (photo courtesy of steep winter storm waves. Woodward-Clyde Consultants). Table 4. Characteristics of fill based on nature of borrow material. Nature of Borrow Material Characteristics of Fill Fairly clean sand Reasonably uniform fill of moderate density (relative density of 40 to 60 percent) Silty or clayey sand Very heterogeneous fill of large void ratio (low relative density) Stiff cohesive soil Skeleton of clay balls, with matrix of sand and clay Soft cohesive soil Laminated normally consolidated or unconsolidated clay. 63 Ho INcelatie Ose leebeelnh Servers. Damage to earth structures or earth parts of structures generally consists of erosion or removal of the soil. The repair consists primarily of replacing the earth material or the protective layer. If permeability or stability of the structure is a problem, the voids can be filled with concrete or asphalt grout. 6. Environmental Considerations. a. Physical Effects. The nature of the soil pore fluid and temperature can influence the behavior of clay soils. A loss in shear strength of marine clays may be realized by removal of the salt due to leaching by freshwater. Changes in moisture content can cause swelling or shrinking of clay soils. Decreasing the temperature of a cohesive soil can cause an expansion of the soil. Fine-grained soils are also susceptible to frost heave. The most significant environmental effect on the physical properties of soils is liquefaction (resulting in loss of strength) due to a seismic event or water wave action. Liquefaction due to either of these causes could result in failure of the structure. The soil properties generally related to this phenomona are saturation, grain size, relative density, and permeability. The problem is generally associated with loose fine sands and silts below the water level at sites in highly seismic areas or areas subject to high breaking waves. Liquefaction of foundation soils under gravity ocean structures due to water wave forces on the structure has been found in offshore work. Liquefac- tion can generally be minimized or mitigated by densification or treatment of the soils, or by providing drainage (rock drains). A discussion of soil response to both seismic and water wave-induced dynamic loads is presented in Callender and Eckert (in preparation, 1983). b. Erosion Effects. The erosion and subsequent deterioration of both natural landforms and manmade coastal structures is of concern. Shore erosion is a major problem along the ocean coastline and the Great Lakes. Erosion is caused principally by storm-induced wave action and associated longshore currents. The processes are further complicated by erosive forces that may come from ice, wind, rain, burrowing animals, or human activity. Shore erosion problems become more critical when beaches become eroded or submerged, and adjoining highly erodible upland areas are subject to direct wave attack (Fig. 12). Unconsolidated sands and silts are generally the most easily eroded, clays and gravels are slightly more resistant, and cemented soils and rock are the least erodible earth materials. The soils may be protected from erosion by various devices such as revetments, seawalls, and bulkheads. Groins may be used to maintain beaches. A detailed discussion of beach erosion is presented in Chapter 4 of the SPM (U.S. Army, Corps of Engineers, CERC, 1977). 7. Uses of Soils in Coastal Construction. a. General. Earth can be used for almost any kind of coastal struc- ture. Coastal structures are generally associated with three types of projects: port and harbor development (including marinas), land reclama- tion, and coastal protection. Design considerations and criteria are 64 -(o8etq ues Fo A4TD Fo Asaqanod ojoyd) etuLoFt Te) ‘oSeatq ues UT SFJTTD YOSUNS FO UOTSOIO OAPM ‘ZI oansty 65 discussed in detail in Callender and Eckert (in preparation, 1983). Soils are used in coastal structures for backfill materials, core materials, slopes and beach restoration. The use of the material is generally associated with the type of development and the type of structure. The choice of material depends on the economy and availability of the material, depth of water, expected water or wave forces, and the purpose of the structure. Some of the various uses are presented in the following paragraphs. b. Offshore Construction. (1) Breakwaters. In rubble-mound breakwaters, submerged reefs, and other coastal rock structures, sand may be used as core material providing other materials are used to protect against wave damage and piping. Clay may be mixed with the sand to reduce permeability, but is generally not adequate core material by itself. The structures may be designed as permeable or impermeable. The soils are usually dredged materials and are placed hydraulically. The core may be covered with filter material and quarrystone riprap or armor units; the number of covering layers depends on the water depth, the design storm waves, and the desired degree of permeability. (2) Caissons. Concrete caissons and sheet-pile cells may be filled with sand and clay. If the surface is to be paved and used for load bearing, sand is preferable to clay because of its higher bearing capacity. A filter layer and armor rock must be provided to cover the fine soils where waves or water currents are expected to impinge on earthfill. c. Shore-Connected Construction. (1) Breakwaters, Jetties and Groins. These structures of rubble- mound construction, caissons, or sheet-pile cells may be filled with soil as described for offshore construction. (2) Low-Cost Shore Protection, Fabric Bags. Low-cost groins and breakwaters have also been constructed by means of fabric bags filled with medium sand or sand-cement. The bags are generally made of nylon, and may be coated with polyvinyl chloride or acrylic to delay fiber degradation by ultraviolet rays. The bags may be filled with available beach sand and used as a low-cost shore protection device. The bags may be filled using a 19-millimeter diaphragm pump or, for more efficiency, a small front-end loader, a hopper, and a jet pump. Typical filled bags measure approximately 3 by 1.5 by 0.5 meter (10 by 5 by 1.5 feet), hold about 1.9 cubic meters (2.5 cubic yards) of sand, and weight about 31 kilonewtons (7 000 pounds). The sand used should be saturated so as to eliminate air pockets which would cause a buoyant force on the bags. Small bags filled with sand (Fig. 13) or concrete (Fig. 14) may be used for protection against erosion. (3) Bulkheads, Quaywalls, and Seawalls. Usually soil materials are used as backfill or foundation materials for bulkheads and walls. Their primary purpose is to provide a level surface or to fill a void behind the structure. The materials can be placed from land, end-dumped from trucks or conveyor belts, or they can be placed hydraulically from dredges; however, the relative density achieved by each method may be widely different. The backfill may be composed of a mixture of all or part 66 Figure 13. Sea cliff upper slope erosion protection by cloth bags filled with sand supported by wood bulkheads, Luecadia, California (photo courtesy of Woodward-Clyde Consultants). Figure 14. Sea cliff shore protection by cloth bags filled with concrete placed in soil bank, Solano Beach, California (photo courtesy of Woodward-Clyde Consultants). 67 of the four component types of soil (gravel, sand, silt, clay); however, not all soil mixtures are equally effective in a given situation. Organic materials are usually considered detrimental and are not used, since they tend to be more compressible and have lower shear strengths. Highly expansive clay should also generally not be used for backfill of coastal structures. A filter layer of gravel or crushed stone is often used (with or with- out a geotextile filter) under and behind walls to provide for relief of hydrostatic pressure and to prevent piping. These materials should meet filter design criteria. (4) Wharves and Piers. The use of earth for wharves and piers is generally as fill behind or for slopes underneath the facility. The natural in-place soils generally provide support for the structures, and foundations are designed in accordance with conventional geotechnical procedures. The purpose of the fill is to help provide stability and rigidity to the struc- ture and to provide useful working areas behind the structure. Most soils may be used for this purpose, but they generally need some type of protec- tion, such as rock riprap and a filter, to mitigate erosion. Coarse- grained granular soils are preferable for use as backfill materials, since they are typically stronger and less compressible. The properties of the backfill soils of use in the design include dry density, water content, shear strength, and compressibility. Other important properties may be the compaction characteristics, permeability, and corrosive characteristics. (5) Land Reclamation. Land reclamation may include dredging for marinas, construction of fills for water-oriented land developments, enlargement of streams, and other related activities in waters and wetlands. These activities generally involve discharge of fill material onto the adjacent shoreline or into waters or wetlands for construction of struc- tures; site development fills for recreational, industrial, commercial, residential, and other uses; causeways or road fills; dams and dikes; artificial islands, property protection; groins and beach restoration; levees and artificial reefs. These fills may be obtained from land sources and dumped by land methods or from water sources and placed hydraulically by dredging. The properties of soils most useful to know in land reclamation projects are the strength characteristics, consolidation characteristics, and chemical properties after placement of the fill. (6) Dikes. Dikes can be constructed of sand, clay, or a combina- tion of both. Earth dikes are usually utilized as containment structures for dredged materials, but may also be used as protective devices such as hurricane barriers. They generally require some type of protection when subjected to wave action. Clay dikes and dikes with a sand core and clay cover have also been built with seaward slopes of 1:6 to 1:10 with a grass cover. (7) Protective Beach and Dune Restoration. The placement of sandfill along a part of shore front is a nonstructural erosion control technique, referred to as beach nourishment, that is utilized for the protection of beach areas or for the creation of protective beaches in areas where none exist. Artificial restoration projects should generally define the source of material, the method of placement, and the grain-size 68 distribution and amount of sand. The sources of material may be either from land or offshore. The methods of placement include placing sand directly on the beach along the entire length of the project, placing it in stockpiles at a feeder beach at one end of the site, and placing it as an offshore bar. The grain size of the materials used should be larger than, or at least the same size as, the original beach material. If coarser sands are used in the beach restoration, the equilibrium slope will be steeper than the existing one, and vice versa for finer particles. A more detailed presentation on beach nourishment may be found in Chapters 5 and 6 of the SPM (U.S. Army, Corps of Engineers, CERC, NAW) 6 A subsand filter system (gravel filter bedding layer placed in the foreshore or offshore zones) may be useful in the stabilization of offshore profiles. Preliminary studies have indicated that such filters may have a stabilizing effect on the bed material in the offshore zone and that they may be effective in speeding accretion in the foreshore zone. The latter use may be employed for berm building or berm replacement (Machemehl, French, and Huang, 1975). The construction of dunes is another type of nonstructural erosion mitigation. Dunes are constructed or enhanced by the placement of sandfill and by the planting of stabilizing vegetation. Snow fences may also be used to physically retain initial sand. Dunes are generally constructed parallel to and behind the beach proper and serve to trap and absorb sand which is transported by onshore winds, storm overwash, or offshore winds blowing over overwash plains. The construction and stabilization of sand dunes is discussed in Chapters 5 and 6 of the SPM (U.S. Army, Corps of Engineers, CERC, 1977). 69 V. PORTLAND CEMENT CONCRETE 1. Introduction. Concrete, a diversified construction material, exists in two physical states--the first as a semifluid or plastic state while being mixed, transported and placed in final forms; the second as a solid after having set and cured. These features of concrete give it a wide application of use in coastal and waterfront structures under many special conditions. Ingredients for making concrete exist in virtually all areas of the world and the use of it in coastal structures depends only on the understanding and knowledge of the materials, design, and processes required for its end use. Concrete has proven to be an excellent construction material. The use of concrete is adaptable to many coastal structures. With good planning it will probably find many additional uses in the future to take advantage of its physical qualities. Concrete can be considered to be made of two components, aggregates and paste. Aggregates are generally classified into two groups, fine and coarse. Fine aggregates consist of sand with particle sizes smaller than 6 millimeters (0.25 inch); coarse aggregates are those with particle sizes greater than 6 millimeters. Aggregates make up about 60 to 80 percent of the concrete. The paste is composed of cement, water, and sometimes admixtures and entrained air. Cement paste ordinarily constitutes 25 to 40 percent of total volume of concrete, cement being 7 to 15 percent and water 14 to 21 percent. Air and admixtures contents may range up to 8 percent. Formulation of concrete in this manner was developed in Portland, England. Subsequently, the term Portland cement concrete has been used to describe cement concretes generally. The durability of Portland cement concrete, defined as its ability to resist weathering action, chemical attack, abrasion, or any other process of deterioration, is a major factor in its excellence as a coastal con- struction material. Durable concrete will retain its original form, quality, and serviceability when exposed to its environment. This section discusses the material used in making concrete, including additives that enhance its properties, the mixing of concrete, and the more important causes of concrete deterioration in coastal structures. It gives suggestions on how to prevent such damage, with particular attention to damage caused by freezing and thawing, aggressive chemical exposure, abrasion, reactive aggregates, and corrosion of embedded materials. Repair methods for concrete that has not withstood the forces of deterior- ation, and the use of protective coatings to enhance durability are also discussed. 2. Types of Portland Cement. Portland cement types and characteristics for coastal structures are specified in ASTM Standards C150-78: (a) Type I cement is used in ordinary structural concrete for foundations, roads, curbs, and ongrade foundations not subject to marine exposure or freezing and thawing conditions. 70 (b) Type IA is a normal air-entraining Portland cement for use in concrete structures, as mentioned for type I cement, subject to freezing climates. (c) Type II cement is a mild sulphate-resisting cement and can be used for concrete in a marine environment not subject to freezing and thawing, if type V (listed below) is not available. However, type II cement concrete is not as durable in seawater as a type V cement concrete. (d) Type IIA cement should be used for concrete in freezing atmospheres. (e) Type III cement is used where a high early strength is needed. Concrete made with this cement will attain a strength in 7 days equivalent to that made with type I cement in 28 days. It should not be used for marine concrete. (f) Type IIIA cement contains an air-entraining agent but other- wise is the same as type III. (g) Type IV cement provides a low heat of hydration in concrete where a heat buildup may occur. It is used in structures such as dams, or in other mass concrete where such heat may be undesirable. (h) Type V cement has a greater resistance to sulfates than all the others and should be used in all marine environments. It has a maximum tricalcium aluminate (C3A) content of 5 percent. Addition of an air-entraining agent is mandatory in freezing climates. (1) Low alkali cement. Federal specifications state that the summation of percentages of Naz0 plus 0.658 of the percentage of K20 shall not exceed 0.6 percent of the total cement content. Low alkali cements are usually well below the 0.6-percent limit. (j) For concrete piles used in soil containing from 0.10 to 0.20 percent water soluble sulfate (as SO,) or used in water containing from 150 to 2 000 parts per million SO,, the concrete should be made with cement containing not more than 8 percent tricalcium aluminate (C3A) such as type II or a moderate sulfate-resistant (MS) cement. In environments where the water soluble sulfate exceeds 0.20 percent or the sulfate solution contains from 2 000 to 10 000 parts per million, Portland cement with the tricalcium aluminate content limited to 5 percent (e.g., type V) should be used. For very severe sulfate exposure (more than 10 000 parts per million), type V cement with a flyash admixture should be used. (k) Where silica in the aggregates is reactive with alkali of the cement, a cement containing less than 0.60 percent alkali should be used. The foregoing alkalis if present in certain amounts may cause swelling of certain aggregates, such as opal or chalcedony. Such swelling can often be reduced by using low alkali cement. 7\ There are many other cements used for special purpagses, such as expan- sive cements, which cause the concrete to expand after setting (not used for marine concrete), waterproof Portland cement, plastic cement (used for making stucco and plaster), oil well cement, and special-blended custom and polymer cements. Si Properties. The basic properties of concrete are placeability, consistency, strength, durability and density. These properties will vary depending on the specific components and ratios of components added during mixing. Well- established relationships governing these properties are discussed below. a. Placeability. Placeability (including satisfactory finishing properties) encompasses traits loosely accumulated in the terms "worka- bility" and "consistency.'' Workability is considered to be that property of concrete which determines its capacity to be placed and consolidated properly and to be finished without harmful segregation. It is affected by the grading, particle shape, and proportions of aggregate, the amount of cement, the presence of entrained air, admixtures, and the consistency of the mixture. These factors are to be taken into account to achieve satis- factory placeability economically. b. Consistency. Consistency, loosely defined, is the wetness of the concrete mixture. It is measured in terms of slump--e.g., the higher the slump the wetter the mixture--and it affects the ease with which the concrete will flow during placement. In properly proportioned concrete, the unit water content required to produce a given slump will depend on several factors. Water requirement increases as aggregates become more angular and rough textured (but this disadvantage may be offset by improve- ments in other characteristics such as bond to cement paste). Required mixing water decreases as the maximum size of the well-graded aggregate is increased. It also decreases with the entrainment of air. Mixing water requirement may often be significantly reduced by certain admixtures. c. Strength. Strength is an important characteristic of concrete, but other, characteristics such as durability, permeability, and wear resistance are often equally or more important. For a given set of materials and conditions, concrete strength is determined by the net quantity of water used per unit quantity of cement. The net water content excludes water absorbed by the aggregates. Differences in strength for a given water- cement ratio may result from changes in maximum size of aggregate; grading, surface texture, shape, strength, and stiffness of aggregate particles; differences in cement types and sources; air content; and the use of admixtures which affect the cement hydration process or develop cementitious properties themselves. However, in view of their number and complexity, accurate predictions of strength must be based on trial batches or experience with the materials to be used. d. Durability. The ability of concrete to withstand environmental exposure is called durability. Concrete must be able to endure those exposures which may deprive it of its serviceability--e.g., freezing and thawing, wetting and drying, heating and cooling, chemicals, and deicing agents. Use of a low water-cement ratio will prolong the life of concrete 72 by reducing the penetration of aggressive liquids. Resistance to severe weathering, particularly freezing and thawing, and to salts used for ice removal is greatly improved by incorporation of a proper distribution of entrained air. Entrained air should be used in all exposed concrete in climates where freezing occurs. By using a suitable cement and a properly proportioned mix, concrete will resist sulfates in soil, ground water, or seawater, provided that concentrations are not in excess of 0.05 molar (7 grams) of NajSO, per liter of water. High-quality concrete will resist mild acid attack, but no concrete has good resistance to strong acids; special protection is necessary in this case. Sometimes concrete surfaces will wear away as the result of abrasive action. In hydraulic structures, particles of sand or gravel in flowing water can erode surfaces. The use of high-quality concrete and, in extreme cases, a very hard aggregate may provide longer durability under these exposures. More detailed discussion of the exposures that impact durability of concrete and of the techniques to resist these impacts is discussed in subsection 6. e. Density. For certain applications concrete may be used primarily for its weight characteristic. To the extent possible, selection of con- crete proportions should be based on test data or experience with the Materials actually to be used. Where such background is limited or not available, estimates given herein may be employed. 4. Components. Concrete is composed principally of cement, aggregates, and water. It will contain some amount of entrapped air and may also contain purposely entrained air obtained by use of an admixture or air-entrained cement. Admixtures are also frequently used for other purposes such as to accel- erate, retard, and improve workability, reduce mixing water requirement, and increase strength, durability, density, and appearance. The required characteristics are governed by the use to which the concrete will be put and by conditions expected to be encountered at the time of placement. These are often, but not always, reflected in specifications for the job. a. Mixing Water For Concrete. (1) General Requirements. Almost any natural water can be used as mixing water for making concrete. Potable freshwater is usually acceptable as satisfactory mixing water but should meet ASTM Standard C94. Water suitable for making concrete, however, may not be fit for drinking. Water high in chlorides should not be used in concrete containing steel reinforce- ment. Water of questionable suitability can be used for making concrete if mortar cubes made with it have 7- and 28-day strengths equal to at least 90 percent of comparison specimens made with tapwater. Mortar cubes should be made and tested according to ASTM Standard C109. In addition, Vicat needle tests (ASTM Standard C191), should be made to ensure that impurities in the mixing water do not adversely shorten or extend the setting time of the cement. Excessive impurities in mixing water also may cause efflorescence, staining, or corrosion of reinforcement. Therefore, certain optional Le limits may be set on chlorides, sulfates, alkalies, and solids in the mixing water. A water source comparable in analysis to any of the waters in Table 5 is probably satisfactory for use in concrete. Table 5. Chemical limits for mixing water. Maximum concentration, ! Test Chemicals (ppm) method? Chloride, as CL ASTM Std. Prestressed concrete or concrete in D512 bridge decks Other reinforced concrete in moist environments or containing aluminum embedments or dissimilar metals or with stay-in-place galvanized metal forms Sulfate, as SO, ASTM Std. D516 Alkalies, as (Na20 + 0.658 K»50) Total solids AASHTO T26 (SEE, Boll) lWash water reused as mixing water in concrete can exceed the listed con- centrations of chloride and sulfate if it can be shown that the concentra- tion calculated in the total mixing water, including mixing water on the aggregates and other sources, does not exceed the stated limits. Other test methods that have been demonstrated to yield comparable results can be used. 3For conditions allowing use of CaCl» accelerator as an admixture, the chloride limitation may be waived by the purchaser. Water containing less than 2 000 parts per million of total dissolved solids can generally be used satisfactorily for making concrete. Water containing more than 2 000 parts per million of dissolved solids should be tested for its effect on strength and time of set. Water containing 2 000 to 3 000 parts per million, not including NajS0O,, of dissolved solids is acceptable if free of organic matter. American Concrete Institute (ACI) Committee 201 (1977), limits chloride ions to percentages of weight according to types of concrete (Table 6). Water for use in prestressed work should be more definitely restricted in salt, silt, and organic contents. It should contain 74 Table 6. Permissible chloride ions. Type of Concrete Maximum (pct) Prestressed concrete Conventionally reinforced concrete in a moist environment and exposed to chloride Aboveground building construction where concrete will stay dry (does not include locations where concrete will be occasionally wetted such as waterfront structures). No limit for corrosion (a) no impurities that will cause a change in time of set greater than 2.5 percent nor a reduction in 14-day strength greater than 5 percent as compared with distilled water; (b) less than 650 parts per million of chloride ion (some authorities permit up to 1 000 parts per million); (c) less than 1 300 parts per million of sulfate ion (some authorities limit this to 1 000 parts per million); and (d) no oil. Seawater may be used, if no other is available, and no steel reinforce- ment is present. The early strength of seawater concrete will be somewhat stronger than that made with freshwater but after about a month the strength of the freshwater concrete will be stronger. At the Port of Los Angeles, thousands of specimens were made for long-time testing using seawater for gaging and tapwater for control specimens. Storage environments were as follows: fog room for controls, air, freshwater and seawater. Compression tests were made at increments of 1 day, 7 days, 28 days, 6 months, 1 year, and thereafter each 5 years through 35 years. The results showed that in the early phases of the program (within the first year) strength gains for the seawater-gaged concrete (compressive strength, modulus of rupture, and modulus of elasticity) slightly exceeded those of the tapwater controls. However, beginning at about 1 year, the tapwater control increased above that of the seawater specimens. At the end of the 35-year period the tapwater series were roughly 15 percent stronger then the seawater series. All concrete mixes were of excellent quality, structural grade concrete and, of course, no form of reinforcement was used. Table 7 compares tapwater to seawater for total dissolved solids. Seawater containing up to 35 000 parts per million of dissolved salts is generally suitable as mixing water for unreinforced concrete. The strength reduction can be compensated for by reducing the water-cement ratio. Quality concrete can be made with seawater if the mix is properly adjusted. 75 Table 7. Typical analyses of city water supplies and seawater. In tapwater (analysis no.) In Dissolved Solids 1 D 6 seawater! Silica (SiQ>) Iron (Fe) Calcium (Ca) Magnesium (Mg) Sodium (Na) Potassium (K) Bicarbonate (HCO3) Sulfate (SO) Chloride (C1) Nitrate (N03) Total dissolved solids 50-480 260-1 410 190-12 200 70-550 iy N ° — OnNWOhR Orr MON e a N rPrRUuNrNHN OOO ° Go oe OG CO UmWOrFNWNO SO 580-2 810 960-20 000 UW - OWOUOWNUMM OO Gn -oO-- Oo a mo ° WUONOouNURORS?’ DPRWODWHAuUOM MOoOCOMmOKRDOO OCOrPNBROKFPOHFOWN SCODHKFNAWWOSO WA he j=) 250.0 125.0 983.0 564.0 19. (=) 35 000 lInifferent seas contain different amounts of dissolved salts. When suitable freshwater is not available, seawater can also be used for making reinforced concrete. Its use may increase the risk of corro- sion, but the risk is reduced if the reinforcement has sufficient cover and if the concrete is watertight and contains an adequate amount of entrained air. Reinforced concrete structures made with seawater and exposed to marine environment should have a water-cement ratio of less than 0.45 and the reinforcement cover should be at least 75 millimeters (3 inches). Seawater should not be used to make prestressed concrete in which the prestressing steel is in contact with the concrete. Sodium or potassium salts present in seawater used for mix water can produce substances that combine with alkali-reactive aggregates in the same manner as when combined with cement alkalies. Therefore, seawater should not be used as mixing water for concrete with known potentially alkali-reactive aggregates, even when the alkali content of the cement is low. (3) Impurities. The following resume discusses the effects of certain impurities in mixing water on the quality of plain concrete. (a) Alkali Carbonate and Bicarbonate. Sodium carbonate can cause very rapid setting, bicarbonate can either accelerate or retard set. In large concentrations the salts can materially reduce concrete strengths. When the sum of these disolved salts exceeds 1 000 parts per million, tests for their setting time and 28-day strength should be made. (b) Chloride and Sulfate. Concern over a high cloride content in the water is chiefly due to the possible adverse effect of chloride ions on the corrosion of reinforcing steel or prestressing strands. The chloride level at which corrosion begins is about 7.6 newtons per cubic meter (1.3 pounds per cubic yard). Placing an acceptable limit on chloride content for any one ingredient, such as mixing water, is difficult consider- ing the several sources of chloride ions in concrete. An acceptable limit 76 in the mixing water depends upon how significantly mixing water contributes to the total chloride content. Suggested limits are shown in Table 5. Water containing less than 500 parts per million of chloride ion generally is considered acceptable. However, the contribution of chlorides from other ingredients also should be considered. (c) Iron Salts. Iron salts in concentrations up to 40 000 parts per million do not usually affect mortar strengths adversely. (d) Miscellaneous Inorganic Salts. Salts of manganese, tin, zinc, copper, and lead in mixing water can cause a significant reduction in strength and large variations in setting time. Of these, salts of zinc, copper, and lead are the most active. Other salts that are espe- cially active as retarders include sodium iodate, sodium phosphate, sodium arsenate, and sodium borate. All can greatly retard both set and strength development when present in concentrations of a few tenths percent by weight of the cement. Generally, concentrations of these salts up to 500 parts per million can be tolerated in mixing water. Another salt that may be detrimental to concrete is sodium sulfide; even the presence of 100 parts per million warrants testing. (e) Acid Waters. Generally, mixing waters combining hydro- chloric, sulfuric, and other common inorganic acids in concentrations as high as 10 000 parts per million have no adverse effect on concrete strength. Acid waters with pH less that 3.0 may create handling problems and should be avoided. (f) Algae. Water containing algae is unsuited for making concrete because the algae can cause excessive reduction in strength either by influencing cement hydration or by causing a large amount of air to be entrained in the concrete. Algae may also be present on aggregates, in which case the bond between the aggregate and cement paste is reduced. b. Polymers in Concrete. (1) General. The following three types of concrete materials utilize polymers to form composites: (1) polymer-impregnated concrete (PIC), which is a hydrated Portland cement concrete that has been impregnated with a monomer and subsequently polymerized in situ; (2) polymer-Portland ccement-concrete (PPCC), which is produced by adding either a monomer or polymer to a fresh concrete mixture and subsequently curing and polymerizing the material in place; and (3) polymer concrete (PC), which is a composite material formed by polymerizing a monomer and aggregate mixture. A monomer is an organic molecular species which is capable of combining chemically with molecules of the same or other species to form a high molecular weight material known as a polymer. A polymer consists of repeating units derived from the monomers which are linked together in a chainlike structure. The chemical process through which these linkages occur is known as polymerization. (2) Polymer-Impregnated Concrete. The selection of suitable monomers for polymer-impregnated concrete (PIC) is based on the impregna- ate tion and polymerization characteristics, availability and cost, and the properties of the resultant polymer and PIC. Liquid vinyl monomer systems have generally been used. Monomers are normally supplied containing an inhibitor to prevent premature polymerization of the monomer. Since polymerization begins immediately on adding a promoter, its use in PIC would be restricted to shallow impregnations. The basic method of producing polymer-impregnated concrete (PIC) consists of the fabrication of precast concrete specimens, ovendrying, saturation with monomer, and in-situ polymerization. For full impregnation, good-quality concrete having a cross section of up to 305 millimeters (12 inches) will require soaking in monomer for about 60 minutes under a pressure of 69 kilopascals (10 pounds per square inch). Concrete may be only partially impregnated when improved strength is not needed but greater durability is desired. (3) Polymer-Portland Cement-Concrete. Polymer-Portland cement- concrete (PPCC) has been prepared with both premixed and postmixed poly- merized materials. The premixed polymerized materials include latexes and polymer solutions or dispersions. The postmix polymerized PPCC has been made with a number of resins and monomers. (a) Polymer Latexes. At present, latex-modified concretes represent the large majority of commerical applications of polymer-modified concretes in the United States. Suitable latex formulations greatly improve the shear bond, tensile, and flexural strength of cements and mortars. (b) Polymer Solutions. Thermosetting water-soluble polymers which have been added to fresh concrete include epoxies, amino-resins, polyesters, and formaldehyde derivatives. Thermoplastic materials include polyvinyl alcohol and polyacrylamides. PPCC process technology is based upon overcoming the incompatibilities of most organic polymers and their monomers with mixtures of Portland cement, water, and aggregate. The mix proportioning of latex PPCC will vary in much the same way as do normal concretes and mortars. (4) Polymer Concrete. Most of the work on polymer concrete (PC) has been with polyester styrene resin systems, and to a lesser extent with furan, epoxy, and vinylester resins systems. The polyester resins are attractive because of moderate cost, availability of a great variety of formulations, and moderately good PC properties. Most of the monomer and resin systems for PC are polymerized at ambient temperatures. Vinyl monomer systems can be polymerized with catalysts such as benzoyl peroxide with an amine promoter. The polyester- styrene systems are polymerized with promoter-catalyst systems such as methylethyl ketone peroxide with cobalt napthanate promoter. Other systems include amine curing agents for epoxy resins. Mixing and placing techniques for PC are based on adaptation of existing equipment and methods for producing Portland cement concrete. A knowledge 78 of polymer chemistry is helpful, but not essential; directions for curing mixes are available from the resin manufacturers. Curing of PC may be performed by thermal catalytic, promoter-catalysts or radiation techniques. Promoter-catalyst systems are frequently best suited for PC, with curing times varied, as needed, between a few minutes and several hours. Full strength is attained when polymerization is completed. PC has been made with epoxy, polyester, and furan resins, and more recently with sytrene monomer systems. c. Aggregates. (1) Normal Aggregates. Normal aggregates consist of clean sand, river-washed gravel, and crushed rock. In certain locations volcanic rock, such as basalt, may be used. They should have clean, hard and uncoated particles and comply with ASTM Standard C33. Other ASTM tests for concrete aggregates are shown in Table 8. Harmful substances may be present in aggregates. These include organic matter, rubbish of all kinds, silt, clay, coal, lignite, dolomitic lime- stones, chalcedonic cherts, opal, cristobalite, some types of volcanic glass, and pyrites. An aggregate containing these substances may be con- sidered as reactive. Materials finer than the No. 200 sieve may form coatings on the aggregates which weaken the bond between the aggregate and the cement paste. Soft particles of aggregate affect the wear resistance and durability of the concrete. Tests used to qualify aggregates to be used to make durable concrete are as follows: (a) Abrasion resistance tests; (b) sulfate soundness tests (used for many years as an index of quality, however, experience has shown that it does not correlate well with the actual performance of aggregates in concrete); (c) tests for organic impurities (on aggregates from new sources) ; (d) laboratory freezing and thawing tests (of limited value, but do furnish useful information for new source material); and (e) tests to determine presence of opal and chalcedony (on aggregates from new sources) by making mortar bars and testing them according to ASTM Standard C342 It is an interesting fact that the water requirement of a given con- sistency for concrete decreases in inverse proportion to the maximum size of the coarse aggregate. For example, a 19-millimeter (0.75 inch) size coarse aggregate would require about 1.49 kilonewtons (335 pounds) of water, per 0.76 cubic meter (1 cubic yard) of concrete; a 50.8-millimeter (2 inch) aggregate would only need about 1.22 kilonewtons (275 pounds) per 0.76 cubic meter (1 cubic yard). The latter would lower the water-cement 79 Table 8. Characteristics and tests of aggregates. Requirement of Characteristic Significance ASTM Standard item reported Resistance to abrasion Resistance to freezing and thawing Resistance to disintegration by sulfates Particle shape and surface texture Grading Bulk unit weight or density Specific gravity Absorption and surface moisture Index of aggregate quality; wear resis- tance of floor pavements Surface scaling, roughness, loss of section, and un- sightliness Resistance to weathering action Workability of fresh concrete Workability of fresh concrete; economy Mix design calcula- tions; classifica- tions Mix design calcula- tions Control of concrete quality Gi275 fine aggregate C128, coarse aggre- gate C29, slag C70 C127 C128 C566 Maximum percent- age of weight loss Maximum number cycles or period of frost immunity; durability factor Weight loss, par- ticles exhibiting distress Maximum percentage of flat and elon- gated pieces Minimum and maxi- mum percent passing standard sieves Compact weight and loose weight C39 C78 Compressive and flexural strength Acceptability of fine aggregate fail- ing other tests Strength to exceed 95 percent of strength achieved with purified sand Definitions of constituents Clear understanding and communications 80 ratio and, of course, produce concrete of a greater strength than that containing the 19-millimeter aggregate. Table 9 shows maximum aggregate sizes for various uses. Table 9. Maximum size of aggregate recommended for various types of construction. he $190.5 mm wide Aggregate Size (mm) (in) heavily reinforced floor and rogf slabs; parapets, cobels and where space is limited >190.5 mm wide with clear distance between reinforcement bars 2 57 mm >305 mm wide unre- inforced sections and Piers, walls, baffles and stilling basin floor slabs in which satisfactory >457 mm wide rein- forced sections with clear distance between reinforcement bars >114.3 mm but < 229 mm Massive sections with clear distance between reinforcing bars 2 229 mm placement of 152.4 mm or cobble concrete cannot be accomplished even though reinforcement spacing would permit the use of larger aggregates. Retaining walls, piers and baffles; in which suitable provision is made for placing concrete containing the larger size aggregate without producing rock pockets or other undesirable results. Gap-graded aggregates can often be used effectively in areas where ASTM C33 standards cannot be met. only one size of coarse aggregate together with sand. A typical gap-graded aggregate may contain In this respect, the resultant concrete would resemble that made with prepacked concrete. When natural aggregates are found to be unacceptable through service records or tests, they may sometimes be improved by removing lightweight, soft, or otherwise inferior particles by processing. (2) Lightweight Aggregate. to produce lightweight concrete. There are a number of materials used Among the natural aggregates are: tuff, 8! pumice, volcanic cinders, scoria, and diatomite rocks. Pumice is fre- quently used in structural concrete. For example, parts of the large concrete counterweights on a bascule bridge (Fig. 15), were composed of normal structural concrete (weight about 23.6 kilonewtons per cubic meter or 150 pounds per cubic foot), lightweight pumice concrete of 15.4 kilonewtons per cubic meter (98 pounds per cubic foot), and heavyweight concrete of 35.3 kilonewtons per cubic meter (225 pounds per cubic foot). Concrete made with pumice weighs from 14.1 to 15.7 kilonewtons per cubic meter (90 to 100 pounds per cubic foot). In the artificial lightweight aggregate family is perlite. This produces a poor grade of concrete weighing from 7.9 to 12.6 kilonewtons per cubic meter (50 to 80 pounds per cubic foot), which is often used as an underlayer for built-up roof decks. It will not produce structural grade concrete. Expanded clay aggregates produce a lightweight, structural quality concrete with densities ranging from 14.1 to 17.3 kilonewtons per cubic meter. Although there are other manufactured lightweight aggregates for making concrete, this report will conclude with vermiculite. Concrete made with the vermiculite (not used for structural concrete) is used extensively as an insulating material and weighs from 5.5 to 11.8 kilonewtons per cubic meter (35 to 75 pounds per cubic foot). (3) Heavy Aggregate. Heavyweight concrete is made with normal coarse aggregates (ASTM Standard C33) and heavy natural or manufactured aggregates such as magnetite (specific gravity 4.2 to 4.4), limonite (Specific gravaty 5.0) to 5. 5)isnandsbawites(specitic joxcavi tyes 5 ntON oe) Some of these minerals could contain pyrite, which can decompose on weather- ing, and should not be used in concrete. Magnetite and limonite should be tested for the presence of pyrite before using in concrete. Manufactured heavy aggregates are usually iron and steel products. Concrete from these products can reach more than 47.1 kilonewtons per cubic meter (300 pounds per cubic foot). More information on heavy aggregates is provided in "Design and Control of Concrete Mixtures" (Portland Cement Association, 1979). (4) Regional Aggregates. For the sake of economy, it may be desireable to use aggregates from the nearest source, unless they contain harmful minerals such as pyrite or chalcedony, even if they do not fully meet with the requirements of ASTM Standard C33. If it is essential to use aggregates containing reactive minerals, pozzolon admixtures are added to reduce or eliminate potential expansion from alkali reactive aggregates. (S) Coral. Coral deposits are found in many oceans of the world. When mined and prepared for use as an aggregate for making concrete, the physical and chemical properties of coral may vary widely. When coral aggregates are used to produce structural concrete, a strength factor is established by using trial mixes until the proper strength has been attained. Cores were taken in 1972 from coral aggregate concrete (made by the Japanese many years prior to 1941), on the island of Kwajalein. The average com- pressive strength of the cores was 13.8 kilopascals (2 000 pounds per Square inch). (6) Chemical Reactions of Aggregates. (a) Types of Reactions. Chemical reactions of aggregates in concrete can affect the performance of concrete. Some reactions may be 82 83 Bascule bridge with light weight concrete counter balances. Pcuneml 5 beneficial, but others result in serious damage to the concrete by causing abnormal expansion, cracking, and loss of strength (Woods, 1968). The reaction that has received greatest attention and was the first to be recognized involves a reaction between alkalies (Na 0 and K,0), from the cement or from other sources with hydroxyl, and certain siliceous con- stituents that may be present in the aggregate. This phenomenon was originally, and is still sometimes, referred to as "alkali-aggregate reaction,'' but in recent years it has been more properly designated as "alkali-silica reaction." Deterioration of concrete has occurred in certain sand-gravel aggre- gates. The deterioration has been regarded as a chemical phenomenon and is a reaction between the alkalies in cement and some siliceous constituents of the aggregates, complicated by environmental conditions that produce high concrete shrinkage and concentration by drying (Hadley, 1968). It has also been clearly demonstrated that certain carbonate rocks participate in reactions with alkalies that, in some instances, produce detrimental expan- sion and cracking. Detrimental reactions are usually associated with argillaceous dolomitic limestones which have somewhat unusual textural characteristics (Hadley, 1964). This reaction is designated as "expansive alkali-carbonate reaction." Other damaging chemical reactions involving aggregates include the oxidation or hydration of certain unstable mineral oxides, sulfates, or sulfides that occur after the aggregate is incorporated in the concrete e.g., the hydration of anhydrous magnesium oxide, calcium oxide, or calcium sulfate, or the oxidation of pyrite) (Mielenz, 1964). Still other reactions may result from organic impurities (such as humus and sugar). Engineers should be aware of these possibilities and supply corrective measures where necessary. Careful testing and examination of the aggregates will usually indicate the presence of such reactive impurities and their use in concrete can be avoided. The alkali-silica, cement-aggregate, and expansive carbonate reactions are most important. (b) The Alkali-Silica Reaction. This reaction can cause expansion and severe cracking of concrete structures and pavements. The phenomenon is complex, and various theories have been advanced to explain field and laboratory evidence (Diamond, 1976). Unanswered questions remain. Apparently, reactive material in the presence of potassium, sodium, and calcium hydroxide derived from the cement reacts to form either a solid nonexpansive calcium-alkali-silica complex or an alkali- Silica complex (also solid) which can expand by imbibition of water. 1 Laboratory Tests for Alkali-Silica Reactivity. service records indicate that reactivity may be possible. The most useful are: (a) Petrographic examination (ASTM Standard C295), (b) mortar bar test for potential reactivity (ASTM Standard C227), eine! (c) chemical test for potential reactivity (ASTM Standard 289). 84 a Petrographic Examination. Petrographic examination provides a recommended practice for the petrographic examination of aggre- gates. Recommendations are available which show the amounts of reactive minerals that can be tolerated. The reactive rocks and minerals that have been more frequently encountered since 1960 appear to have larger potassium proportions and are harder to recognize in petrographic examination. Highly deformed quartz with an angle of undulatory extinction of 35 to 50° or more and with deformation lamellae appear characteristic of the reactive quartz-bearing rocks. Relatively coarse-grained micas have also been regarded as reactive constituents; fine-grained micas are reactive in argillites (Dolar-Mantuani, 1969). b Mortar Bar Test for Potential Reactivity. This test is the method most generally relied on to indicate potential alkali reactivity. Acceptance criteria are given by ASTM Standard C33 for evaluat- ing these test results. The procedure is useful not only for the evaluation of aggregates, but also for the evaluation of specific aggregate-cement combinations. However, criteria have not been developed for the metamor- phic siliceous and silicate rocks. c Chemical Test for Potential Reactivity. This test is the method used primarily for a quick evaluation of natural aggregates. The results are obtainable in a few days as compared with 3 to 6 months or more with the mortar bar test. Acceptance criteria for this test are given in ASTM Standard C33. Care must be exercised in interpreting the results of this test. This test method has given questionable results when evaluat- ing lightweight aggregates; therefore, it is not recommended for this purpose (Ledbetter, 1973). 2 General Criteria for Judging Reactivity. When avail- able, the field performance record of a particular aggregate, if it has been used with cement of high alkali content, is the best means for judging its reactivity. If such records are not available, the most reliable criteria are petrographic examination with corroborating evidence from the mortar bar test (U.S. Army, Corps of Engineers, 197lc), sometimes supplemented by tests on concrete although these have not been standardized. The chemical test results should also be used in conjunction with results of the petrographic examination and mortar bar test. It is preferable not to rely on the results of only one kind of test in any evaluation (U.S. Army, Corps of Engineers, 1971c). 3 Recommended Procedures with Alkali-Reactive Aggregates. If aggregates are shown by service records or laboratory examination to be potentially reactive, they should not be used when the concrete is to be exposed to seawater or alkali environments if nonreactive aggregates are available (Highway Research Board, 1958). When reactive aggregates must be used, this should be done only after thorough testing, and preferably after service records have established that, with appropriate limits on the alkali content of the cement, or with the use of appropriate amounts of an effective pozzolan, or both, satisfactory service can be anticipated. In cases where seawater or alkaline soil environments are not involved, and there are no sound materials available economically, reactive materials may be used provided certain limits are set in the specifications: 85 (a) Specify a low alkali cement having a maximum of 0.6 percent equivalent Naj20. (b) prohibit the use of seawater or alkali soil water as mixing water; (c) avoid addition of sodium or potassium chloride; and (d) where low alkali cements are not economically available, use a suitable pozzolanic material as prescribed by ASTM Standard C618 and tested in accordance with ASTM Standard C441 (to determine their effectiveness in preventing excessive expansion due to the alkali-aggregate reaction). Whenever the use of pozzolanic materials is considered, it should be remembered that if these materials increase water demand, they may cause increased drying shrinkage in concrete exposed to drying. Increased water demand results from high fineness and poor particle shape. The rate of strength development in correctly proportioned pozzolanic concrete can equal that of Portland cement concretes, i.e., 28 days. (c) Cement-Aggregate Reaction. Recent research indicates that the cement-aggregate reaction is mainly a reaction between the alkalies in the cement that produce high pH and abundant hydroxyl and siliceous constituents of the aggregates. However, the field performance of con- cretes made with reactive sand and gravels does not correlate well with cement alkali content. The concrete deterioration results from moderate interior expansion caused by alkali-silica reactivity, and surface shrinkage caused by severe drying conditions. Evaporation at the surface of the concrete causes an increase in alkali concentration in the pore fluids near the drying surface, and a net migration of alkali toward this surface. Under these conditions even a low alkali cement may cause objectionable deterioration, particularly near the surface. This alkali distribution is altered by the leaching of alkalies near the surface during periods of heavy rain (Hadley, 1968). 1 Identification by Laboratory Tests. Although special tests, such as ASTM Standard C342, have been devised to indicate potential damage from this phenomenon, their reliability is doubtful. 2 Recommended Procedure to be Employed with Potentially Deleterious Cement-Aggregate Combinations. The use of potentially de- leterious cement-aggregate combinations should be avoided where possible. However, if they must be used, a suitable pozzolan that does not increase drying shrinkage and 30 percent or more (by weight) of coarse limestone should be used with potentially deleterious cement-aggregate combinations. Concrete tests should be used to determine whether the resulting combina- tion is satisfactory. (d) Expansive Alkali-Carbonate Reactivity. Certain limestone aggregates, usually dolomitic, have been reported as reactive in concrete structures. There are many unanswered questions, and more than one mech- anism has been proposed to explain expansive carbonate reactivity. The affected concrete is characterized by a network of pattern or map cracks 86 usually most strongly developed in areas of the structure where the concrete has a constantly renewable supply of moisture, such as close to the water- line in piers, from the ground behind retaining walls, beneath road or sidewalk slabs, or by wick action in posts or columns. A distinguishing feature from alkali-silica reaction is the general absence of silica gel exudations at cracks. Additional signs of the severity of the reaction are closed expansion joints with possible crushing of the adjacent concrete (Hadley, 1964). 1 Identification by Laboratory Tests. The most useful laboratory tests are discussed below. a Petrographic Examination. This examination of aggregates may be used to identify the features of the rock. The presence of all or any dolomite in a fine-grained carbonate rock makes it desirable to perform the rock cylinder test (ASTM Standard C586). This is recommended whether or not the texture is believed to be typical, and whether or not insoluble residue including clay amounts to a substantial part of the aggregate. As expansive rocks are recognized from more areas, the more yariable the textures and compositions appear to be. b Expansion of Concrete Prisms Test. This test is performed with prisms made of job materials and stored at 100 percent relative humidity at 250 Celsius, (735. Farenheit), or (in order to accel- erate the reaction) the prisms may be made with additional alkali and stored at elevated temperature. The comparison is usually made with the expansion of prisms containing a nonreactive control aggregate. c Petrographic Analysis. A petrographic analysis of the concrete can confirm the type of aggregate present and its character- istics. Distress that has occurred in the aggregate and surrounding matrix, such as microcracking and macrocracking, may be observed. Reaction rims, which do not necessarily signify harmful results, may be observed in certain aggregate particles and may be identified as negative or positive by acid etching. Secondary deposits of calcium carbonate, calcium hydroxide, and ettringite (calcium sulfoaluminate) may be found in voids within the con- crete; however, there are no deposits of silica, hardened or in gel form, associated with the suspect aggregate pieces. d Other Laboratory Tests. Additional tests on alkali- carbonate reaction include identifying by visual observation sawed or ground surfaces. X-ray examination of reaction products is also sometimes useful. e Criteria for Judging Reactivity. Several criteria are available for judging the reactivity of aggregates. These include definitive correlations between expansions occurring in the laboratory in rock cylinders or concrete prisms and deleterious field performance which have not yet been established. The factors involved are complex and include the heterogeneity of the rock, coarse aggregate size, permeability of the concrete, and seasonal changes in environmental conditions in service, principally availability of moisture, level of temperature, and possibly the use of sodium chloride as a deicing chemical. 87 It is not certain that rapid determination of potential reactivity can always be made by using the rock cylinder test, because some rocks showing an initial contraction may develop considerable expansion later on. Expansions greater than 0.10 percent in the rock cylinders are usually taken as a warning that further tests should be undertaken to determine expansion of the aggregate in concrete. Fortunately, many carbonate rocks that expand in rock cylinders do not expand in concrete. 2 Recommended Procedures to Minimize Alkali-Carbonate Reactivity. Procedures that can be employed to mitigate the effects of the reaction include: (a) Avoiding reactive rocks by selective quarrying; (b) dilution with nonreactive aggregates, or use of a smaller maximum size; and (c) use of low alkali cement (probably 0.4 percent combined alkali or lower), which will prevent harmful expansions in most cases; however, in pavements where sodium chloride is used as a deicing chemical, this cannot be taken as certain. Of these measures, the first is the safest and usually the most econ- omical. (e) Preservation of Concrete Containing Reactive Aggregate. There are no known methods of adequately preserving existing concrete which contains the elements that contribute to the previously described chemical reactions. Water or moisture is partly involved in at least two of these reactions. The destructive effects of freezing and thawing are more pro- nounced after the initial stages of destruction by these chemical reactions. Therefore, any practicable means of decreasing the exposure of such concrete to water may extend its useful life. d. Admixtures. (1) General. An admixture is defined as a material other than water, aggregates, and hydraulic cement, that is used as an ingredient of concrete or mortar and is added to the batch immediately before or during its mixing. ASTM Standard C494 classifies certain chemical admixtures in terms of function as follows: (a) Type A, water-reducing admixtures, (b) Type B, retarding admixtures, (c) Type C, accelerating admixtures, (d) Type D, water-reducing and retarding admixtures, and (e) Type E, water-reducing and accelerating admixtures. These admixtures are discussed according to the type of materials con- situting the admixture or to the characteristic effects of their use. 88 (2} Water-Reducing and Retarding Admixtures. Water-reducing admixtures are used to improve the quality of concrete, to obtain specified strength at lower cement content, or to increase the slump of a given mixture without increase in water content. They also may improve the properties of concrete containing aggregates that are harsh or poorly graded, or both, or may be used in concrete that must be placed under difficult conditions. Set-retarding admixtures delay the onset of harden- ing, prolonging the period when the concrete is workable. Both types of admixtures are useful when placing concrete by means of a pump or when using a tremie process. The materials that are generally available for use as water-reducing admixtures and set-retarding admixtures fall into four general classes: (a) Lignosulfonic acids and their salts; (b) modifications and derivatives of lignosulfonic acids and their salts; (c) hydroxylated carboxylic acids and their salts; and (d) modifications and derivatives of hydroxylated carboxylic acids and their salts. Hydroxylated carboxylic acid salts act as water-reducing, nonair- entraining retarders. Lignosulfonates are available as the calciun, sodium or ammonium salts. Admixtures of classes (a) and (c) can be used either alone or combined with other organic or inorganic, active or essen- tially inert substances. They are water-reducing, set-retarding admixtures. Admixtures of classes (b) and (d) are water-reducing admixtures offered as combinations of substances designed either to have no substantial effect on rate of hardening or to achieve varying degrees of acceleration or retardation in rate of hardening of concrete; these admixtures may include an air-entraining agent. The composition of the Portland cement affects the air-entraining properties of lignosulfonate admixtures in concrete. Concrete containing a lignosulfonate retarder generally requires 5 to 10 percent less water than comparable concrete without the admixture. Compressive strengths at 2 or 3 days are usually equal to or higher than those of corresponding concrete without the admixture and the strength at 28 days or later may be 10 to 20 percent higher. Lignosulfonic acid salts, carboxylic acid salts, or modifications or derivatives thereof can be mixed or reacted with other chemicals that entrain air, modify setting time, or affect the strength development of concrete. Calcium chloride, neutralized wood resins, alkyl aryl sulfo- nates, and triethanolamine are examples of additives that have been used. The use of compounded or modified water reducers usually causes a water reduction of 5 to 10 percent at equal air content. Compressive strengths at ages greater than 2 days are usually from 10 to 20 percent higher than those of similar concretes without admixture. (3) Accelerating Admixtures. Accelerating admixtures are added to concrete either (a) to increase the rate of early strength development, (b) to shorten the time of setting, or (c) for both purposes. Chemicals which 89 accelerate the hardening of mixtures of Portland cement and water include some of the soluble chlorides, carbonates, silicates, fluosilicates, and hydroxides (Steinour, 1960), and also some organic compounds such as triethanolamine (Newman, et al., 1943). Calcium aluminate cements and finely ground hydrated Portland cement have also been advocated. Some of the soluble chlorides, particularly calcium chloride (Highway Research Board, 1952) and to a much lesser extent triethanolamine, have general applicability as admixtures in concrete. Some of the other materials are suitable only for use in the preparation of quick-set cements. By far the best known and most widely used accelerator is calcium chloride. Many other materials have been found to accelerate the strength gain of concrete but, in general, they are seldom used, and only limited information concerning their effect on the properties of concrete is available. Most of the information given on accelerators applies mainly to the use of calcium chloride. The effects of accelerators on some of the properties of concrete are as follows: (a) The setting time, initial and final, is reduced. The amount of reduction varies with the amount of accelerator used, the temperature of the concrete, and the ambient temperature. Excessive amounts of the accelerator may cause rapid setting. (b) Less air-entraining admixture is required to produce the required air content. However, in some cases larger bubble sizes and higher spacing factors are obtained. (c) Earlier heat release is obtained but there is no appreciable effect on the total heat of hydration. (d) Compressive strength is increased substantially at early ages. The ultimate strength may be reduced slightly. The increase in flexural strength is usually less than that of the compressive strength. (e) It is generally considered that the volume change is increased for both moist curing and drying conditions. There is a question of the degree of the effect caused by the accelerators as opposed to other factors influencing volume change. (f) The resistance to freezing and thawing and to scaling caused by the use of deicing salts is increased at early ages, but may be decreased at later ages. (g) The resistance to sulfate attack is decreased. (h) The expansion produced by alkali-aggregate reaction is greater. This can easily be controlled by the use of low alkali cement or pozzolans. (i) Corrosion of metals may occur, especially in the use of calcium chloride when steam curing is employed. The use of calcium chloride in recommended amounts does not cause progressive corrosion 90 of conventional steel reinforcement in typical reinforced concrete under normal conditions where the bars have sufficient concrete cover. Stannous chloride when properly used acts as an accelerator and does not cause corrosion of the steel even when steam curing is used. (4) Calcium Chloride. Calcium chloride is available in two forms. Regular flake calcium chloride, ASTM Standard D98 (type 1), contains a minimum of 77 percent CaCly. Concentrated flake, pellet, or granular calcium chloride ASTM Standard D98 (type 2) contains a minimum of 94 percent of CaCl5. Calcium chloride can generally be used safely in amounts up to 2 percent by weight of the cement (McCall and Claus, 1953). Larger amounts may be detrimental and, except in rare instances, provide little additional advantage. The benefits of the use of calcium chloride are usually more pronouned when it is employed in concrete with a mixing and curing temperature below 21 Celsius (70° Farenheit). At high mixing and curing temperatures long-term strength, especially flexural strength, may decrease, and shrinkage and cracking may increase. Laboratory tests have indicated that most increases of compressive strengths of concrete resulting from the use of 2 percent of calcium chloride by weight of cement are in the range of 2 760 to 6 890 kilopascals (400 to 1 000 pounds per square inch) at 1 to 7 days for 21° Celsius curing. At 4.4 Celsius (40 Farenheit) curing the increases in strengths obtained at_1 and 7 days with calcium chloride are in the same range as that for 21 Celsius curing. The increase in strength usually reaches its maximum in 1 to 3 days and thereafter generally decreases. At 1 year, some increase is still evident in concrete made with most cements. The specific effect of the use of calcium chloride varies, however, for different cements as is indicated by the range of strength increases cited above for the early ages. The relative increase in flexural strength of concrete resulting from the use of 1 or 2 percent of calcium chloride is not as great as the increase in compressive strength. Calcium chloride increases the flexural strength at 1 and 3 days, but decreases the flexural strength at 28 days or at later ages (McCall and Claus, 1953). Flexural strengths of concretes containing 1 to 2 percent calcium chloride are usually increased over the strengths of similar concrete without the admixture by 40 to 90 percent at 1 day and by 5 to 35 percent at 3 days, respectively, when moist cured at 21 Celsius. At 28 days, decreases of up to 12 percent have been reported from laboratory tests of moist-cured concrete. The use of 1 percent calcium chloride by weight of the cement is sufficient in most cases to accelerate setting and increase strength sufficiently for cold weather concreting, with the understanding that cold weather protection is provided. The selection of the optimum amount should be based on the type of cement, the temperature of the concrete, and the ambient air temperature. Calcium chloride may promote corrosion of the usual reinforcement in concrete even though adequate concrete cover is provided for the steel. 9 However, it should not be used where stray electric currents are expected and should not be used in prestressed concrete because of possible stress corrosion of the prestressing steel (Arber and Vivian, 1961). Calcium chloride in concrete may be expected to aggravate corrosion of embedded galvanized metal and of galvanized forms that are left in place. Combina- tions of metals, such as aluminum-alloy electrical conduit and steel reinforcing, should not be used in concrete exposed to water. Calcium chloride may be especially beneficial for concrete exposed to low or freezing temperatures at early ages if used as recommended in the ACI Standard ACI 604-56. Calcium chloride increases the rate of early heat development and accelerates the set, but lowers the freezing point of the water in concrete only to an insignificant extent. (5) Air-Entraining Admixtures. Many materials, including natural wood resins, fats, and oils, may be used in preparing air-entraining admixtures. These materials are usually insoluble in water and generally must be chemically processed before they can be used as admixtures. Since not all such materials produce a desirable air-void system, air-entraining admixtures should meet the requirements of the ASTM Standard C260. Air-entrained concrete containing a large number of very small air bubbles is several-fold more resistant to frost action than nonair-entrained concrete made of the same materials. Air-entrained concrete should be a dense, impermeable mixture that is well-placed, protected, finished, and cured if maximum durability is to be obtained. Air entrainment, while improving both workability and durability, may reduce strength. Within the range of air content normally used, the decrease in strength usually is about proportional to the amount of air entrained. For most types of exposed concrete a slight reduction in strength is far less significant than the improved resistance to frost action. The reduction in strength will rarely exceed 15 percent in the case of compressive strength and 10 percent in the case of flexural strength. In some installations of precast concrete units such as cribbing and curbing, there is considerable exposure to freezing and thawing action. The use of adequately prepared and controlled air-entrained concrete is the best way to improve resistance to freezing and thawing. (6) Air-Detraining Admixtures. There have been cases where aggregates have released gas into, or caused excessive air entrainment, in plastic concrete which made it necessary to use an admixture able to dissipate the excess air or other gas (MacNaughton and Herbich, 1954). Also, it is sometimes desirable to remove part of the entrained air from a concrete mixture. Compounds such as tributyl phosphate, diburyl phthalate, water-insoluble alcohols, and water-insoluble esters of carbonic and boric acids, as well as silicones, have been proposed for this purpose; however, tributyl phosphate is the most widely used material. (7) Admixture to Reduce Alkali Aggregate Expansion. Test data indicate that small additions of certain chemical substances may be effec- tive in decreasing expansion resulting from alkali-aggregate reaction (McCoy and Caldwell, 1951). Outstanding reductions in expansion of labora- 32 tory mortar specimens have been reported for additions of 1 percent by weight of the cement of lithium salts and for additions of about 2 to 7 percent of certain barium salts. Moderately reduced expansions were also obtained with certain protein air-entraining admixtures and with some water-reducing, set-retarding admixtures. It was found that some of these substances were more effective in reducing expansion than others. The results reported are limited and further work is needed. There is some evidence that expansions due to alkali-aggregate reaction are slightly lowered by air entrainment and the use of low alkali cement. (8) Expansion Admixtures. Admixtures, which during the hydration period of concrete or grout expand themselves or react with other con- stituents of the grout to cause expansion, are used to minimize the effects of dry shrinkage. They are used in both restrained and unrestrained placement. The most common admixtures for this purpose is finely divided iron and chemicals to promote oxidation of the iron. This use is generally limited to relatively small projects. Expansive cements are most often used on large projects. (9) Shrinkage Preventing Admixtures. Three different shrinkage- compensating cements are described in ASTM Standard C845 and are designated as Type K, Type S, and Type M. The expansion of each of these cements when mixed with sufficient water is due principally to the formation of ettrin- gite. Most shrinkage-compensating cements consist of constituents of conventional portland cement with added sources of aluminate and calcium sulfate. The three types of expansive cements differ from each other in the form of the aluminate compounds from which the expansive ettringite is developed. The principal constituents of these cements are: (a) Type K Portland cement, calcium sulfate, and Portland-like cement containing anhydrous tetracalcium trialuminate sulfate; (b) Type M Portland cement, calcium sulfate, and calciumaluminate cement; and (c) Type S Portland cement high in tricalcium aluminate and calcium sulfate. An important requirement is the selection of material proportions so that the Ca, S3, and especially the Al»03 become available for ettringite formation during the appropriate period after the mix water is added. Determination of these proportions should be based on test results in accordance with ASTM Standard C806. (10) Bond Improvement Admixtures. Bonding admixtures are water emulsions of several organic materials that are mixed with Portland cement or mortar grout for application to an old concrete surface just prior to placing topping or patching mortar or concrete, or are mixed with the topping or patching material. Common bonding admixtures are made from polymers that include polyvinyl chloride, polyvinyl acetate, acrylics, and butadiene-styrene copolymer. Bonding agents usually cause entrainment of air and a sticky consistency in grout mixtures. (11) Penetration and Plasticity Admixtures. Admixtures which improve the ability of freshly mixed concrete and grout to penetrate into voids and cracks also increase the plasticity of the mix. The degree of 93 plasticity of fresh concrete, the amount of surface area of the solids per unit of water volume, will determine the bleeding characteristics and workability of concrete and grout. A low ratio of surface area of solids to volume of water results in a thin and watery paste; consequently, the aggregate particles are only slightly separated and the mixture lacks plasticity and tends to segregate. The ratio of surface area of solids to volume of water may be increased by increasing the amount of cement or by adding a suitable mineral admixture to the mix. Admixtures that are relatively chemically inert, such as ground quartz or limestone, cemetitious materials such as natural cements, hydraulic limes or slag cements, and pozzolans are commonly used. (12) Impermeability Admixtures. Concrete and grout are not impermeable to the penetration of water; however, the terms waterproofing" or ''damp proofing'' have come to mean a reduction of rate of penetration of water into dry concrete and grout. Admixtures comprised of fatty acids, usually calcium or ammonium stearate or oleate, which also cause air entrainment during mixing. Also used are mineral oils, asphalt emulsions, and certain cut-back asphalts. (13) Corrosion Inhibiting Admixtures. In the manufacture of certain concrete products containing steel, it might be desirable to accelerate the rate of strength development by use of both a chemical accelerator and heat. The latter is usually in the form of steam at atmospheric pressure. When calcium chloride is used as the accelerator in this type of curing, laboratory studies have found the rate of corrosion of the steel to be accelerated. However, Arber and Vivian (1961) found that certain compounds containing an oxidizable ion such as stannous chloride, ferrous chloride, and sodium thiosulfate, act as accelerators as does calcium chloride, but also appear to cause less corrosion than the latter. Stannous chloride appeared to be the best of the products tried and 2 percent of the salt by weight of cement was more effective than 1 percent, and as effective as greater amounts, both from the standpoint of acceleration and resistance to corrosion. For effective use, the salt must be added to the concrete in the stannous form and a dense concrete must be used. (14) Color Admixtures. Pigments are often added to produce color in the finished concrete. The requirements of suitable coloring admixtures include: (a) color fastness when exposed to sunlight; (b) chemical stability in the presence of alkalinity produced in the set cement; (c) no adverse effect on setting time or strength develop- ment of the concrete; and (d) stability of color in autoclaved concrete products during exposures to the conditions in the autoclave. Pigments frequently used to color concrete are: (a) Grays to black--black iron oxide, mineral black, carbon black, 94 (b) Blue--ultramarine blue, Phthalocyanine blue, (c) Red--red iron axide, (d) Brown--brown iron oxide, raw and burnt amber, (e) Cream or buff--yellow iron oxide, (f) Green--chromium oxide, phthelocyanine green, and (g) White--titanium dioxide, 5. Preparation of Concrete Mixes. There are standard methods for selecting proportions for concrete made with aggregates of normal density and of workability suitable for usual cast-in-place construction. The methods provide a first approximation of proportions and are intended to be checked by trial batches in the labora- tory or field and adjusted, as necessary, to produce the desired character- istics of the concrete. a. Selection of Mix Proportions. The procedure for selection of mix proportions given in this section is applicable to normal weight concrete. Estimating the required batch weights for the concrete involves a sequence of logical, straightforward steps which, in effect, fit the characteristics of the available materials into a mixture suitable for the work. Regard- less of whether the concrete characteristics are prescribed by the speci- fications or are left to the individual selecting the proportions, estima- tion of a total batch weight per cubic unit of concrete can best be accom- plished by referring to the table used in (7) below. (1) Choice of Slump. If slump is not specified, a value appro- priate for the work can be selected from Table 10. The slump ranges shown apply when vibration is used to consolidate the concrete. Mixes of the stiffest consistency that can be placed efficiently should be used. Table 10. Recommended slumps for various types of construction. Types of construction Reinforced foundation walls and footings Plain footings, caissons, and substruc- ture walls Beams and reinforced walls Building columns Pavements and slabs Mass concrete May be increased 25 mm for methods of consolidation other than vibration. 95 (2) Choice of Maximum Size of Aggregate. Large maximum sizes of well-graded aggregates have less voids than smaller sizes. Hence, concretes with the larger sized aggregates require less mortar per unit volume of concrete. Generally, the maximum size of aggregate should be the largest that is economically available and consistent with dimensions of the struc- ture. In no event should the maximum size exceed one-fifth of the narrowest dimension between sides of forms, one-third the depth of slabs, nor three- fourths of the minimum clear spacing between individual reinforcing bars, bundles of bars, or pretensioning strands. (3) Estimation of Mixing Water and Air Content. The quantity of water per unit volume of concrete required to produce a given slump depends on the maximum size, particle shape, and grading of the aggregates, and on the amount of entrained air. It is not greatly affected by the quantity of cement. Table 11 provides estimates of required mixing water for concretes made with various maximum sizes of aggregate, with and without air entrain- ment. Depending on aggregate texture and shape, mixing water requirements may be somewhat above or below the tabulated values, but they are suf- ficiently accurate for the first estimate. Such differences in water demand are not necessarily reflected in strength. Table 11 indicates the approximate amount of entrapped air to be expected in nonair-entrained concrete in the right side of the table and shows the recommended average air content for air-entrained concrete in the left side of the table. The use of normal amounts of air entrainment in concrete with a specified strength near or about 34 megapascals (5 000 pounds per square inch) may not be possible due to the fact that each added percent of air lowers the maximum strength obtainable with a given combina- tion of materials (Tuthill, 1960). When trial batches are used to establish strength relationships or verify strength-producing capability of a mixture, the least favorable combination of mixing water and air content should be used. This is, the air content should be the maximum permitted or likely to occur, and the concrete should be gaged to the highest permissible slump. This will avoid developing an overoptimistic estimate of strength on the assumption that average rather than extreme conditions will prevail in the field. (4) Selection of Water-Cement Ratio. The required water-cement ratio is determined not only by strength requirements but also by factors such as durability and finishing properties. The average strength selected must, of course, exceed the specified strength by a sufficient margin to keep the number of low tests within specified limits (Table 12). For severe conditions of exposure, the water-cement ratio should be kept low even though strength requirements may be met with a higher value. Table 13 gives limiting values. (5) Calculation of Cement Content. The amount of cement per unit volume of concrete is fixed by the determinations made above. The required cement is equal to the estimated mixing water content divided by the water-cement ratio. If, however, the specification includes a separate minimum limit on cement in addition to requirements for strength and durability, the mixture must be based on whichever criterion leads to the larger amount of cement. The use of pozzolanic or chemical admixtures will affect properties of both the fresh and hardened concrete. 96 *suoTzeoTFtoeds poqdesse FO SZIWT]T UTYIM popers sojzedoisde asi1e0d zer[nsue podeys-T[om AT qeuoseet TOF WNUTXeW o1e oy, *Seud.eq [eT TOF Si1o0,OeF Jusued Butyndwod ut asn LOZ Oe 10}eM BUTXTW FO setqtquenb aSOULe ‘qusoa0d snutu 10 sn{dz ‘(~S-€19 IDV) 93eL9U0D 10F SUOTILOdoOIg BUTIDETEg IOF 9dTIDeIg popuowMOdey woz pordepy, noonnstm Ul te) ee oss c°0 5 0) S°0 O°T Seal OG Suc O° 20 pet! Calcium sulfate Sodium Ammonium Chlorine (gas) hydroxide chloride Seawater Magnesium Softwater chloride Sodium cyanide Calcium Ammonia hydroxide chloride (liquid) Negligible Oxalate |= | ! opm Se Mean SO) BO) ws and beam l., \ = 8 underdrain and outlet — 1 | | Cross walls are to stop at | this line SS lS | Two bulb piles replace “O 3 pedestal pile when sheetpiles : | conflict with pedestal pile. D = | SSeS \ | Interlocking I sneetpiles eae’ SECTION ¢ 47; aay 3-1"x 3°!" pedestol —.—— | D-D : SECTION C-C b= 4] Figure 24. Concrete combination stepped and curved-face seawall (U.S. Army, Corps of Engineers, CERC, 1977). 149 Pioneer Point, Cambridge, Maryland (before Courtesy of Portland Cement Association pel @ expansion joint re s El. 9.00’ SECTION AT JOINT 4" Flap valve H.Water E!l. 4.60° M.H.W, El. 3,68 Figure 25. Concrete revetment (U.S. Army, Corps of Engineers® CER. 1977). 150 ¥ s j ao 7 te g : y “ OP r p : A “ - “ \ - F g ¢ / “ é ‘ mo. 4 fy Pp ro as. : ign ee © 4 # Pa sof ce a We oA E Fue a & Figure 26. Articulated armor unit revetment (photo courtesy of Marine Modules Inc.). flexibility is required, timber wales have been used. Permeable-type concrete groins have been built in the past that permitted the passage of sand through the structure but are not used at present. In low wave climates grout-filled bags are also used as an installation convenience; the bags, usually plastic, deteriorate leaving the small concrete shapes as protection of the groins. d. Jetties and Breakwaters. In exposed locations, jetties and break- waters are generally some variation of a rubble-mound structure containing concrete either as a binding material to hold rock together or as separate elements of breakwaters having a heavy weight as well as energy absorption characteristics. Some types of jetties are illustrated in Figures 28 and 29. In less severe exposures, both cellular steel and concrete caissons have been used. In low wave climates grout filled bags are used. Where rock armor units in adequate quantities or size are not econom- ically available, concrete armor units are used. Also, concrete sheet piles are sometimes used as core for jetties. Figure 30 illustrates the use of Quadripod armor units on the rubble-mound jetty at Santa Cruz, California. Figure 29 illustrates the use of the more recently developed dolos armor unit where 374- and 383-kilonewton (42 and 43 ton) dolosse were 151 \ Jupiter Island, Florida (1965) Courtesy of Carthage Mills Inc. Erosion Contral Division +1 {0 ft. £ Reinforced concrete z vescreen Plastic filter cloth Interlocking blocks Reinf. cone.cap 16° 4 : ~~ 05" to 1.0"Gravel on plastic filter cloth, iG 8" thick Plastic filter cloth as far down as possible. Prestressed concrete piling -ILO ft. =i Section A-A ec Ship-lap Joint fale nee oe Section A-A 101234 5t 4 “TV 14" block Scole Figure 27. Interlocking concrete block revetment (U.S. Army, Corps of Engineers, CERC, 1977). 152 Figure 28. Fabric tubes filled with concrete form a jetty (photo courtesy of Fabriform). used to rehabilitate the seaward end of the Humboldt Bay jetties against 12-meter (40 foot) breaking waves (Magoon and Shimizu, 1971). (1) Concrete Caisson Breakwater. Breakwaters of this type are built of reinforced concrete shells that are floated into position, settled on a prepared foundation, filled with stone or sand for stability, and then capped with concrete or stones. These structures may be constructed with or without parapet walls for protection against wave overtopping. In general, concrete caissons have a reinforced concrete bottom, although open-bottom concrete caissons have been used. The open-bottom type is closed with a temporary wooden bottom that is removed after the caisson is placed on the foundation. The stone used to fill the compartments combines with the foundation material to provide additional resistance against horizontal movement. Figure 31 illustrates a patented perforated type of caisson breakwater (Jarlan, 1961). The installation at Baie Comeau, Quebec (Stevenston, 1963), utilized the caisson as a wharf on the harborside. The holes or perforations on the seaward side reduce the undesirable conditions of a smooth vertical face wall and are an illustration of complex structural shapes possible because of the way concrete is cast. (2) Concrete Armor Units. Many different concrete shapes have been developed as armor units for rubble structures. The major advantage of concrete armor units is that they usually have a higher stability coefficient value, thus permitting the use of steeper structure side slopes or a lighter weight of armor unit. This property is especially valuable when quarrystone of the required size is not available. 153 cSt : Humboldt Bay, Se California (1971) Existing Concrete Cap 42 Tons Dolos (2 Layers) Head South Jetty 10-14 Ton Stone 4' Thick Bedding Existing Structure Layer (after Magoon and Shimizu,1971) Figure 29. Dolos rubble-mound jetty (U.S. Army, Corps of Emenineeras, GING. 1977/7) 154 __** in sees Santa Cruz, California ( 1963) CHANNEL SIDE SEAWARD SIDE Concrete Cap B- Stone Concrete Filled EL +15.0' ELOO ee a Ls “Single Row ff Xj 25-Ton Quadripods C-—Stone Core Existing Ground STESTISTIESTIRSISTI ST RSISTIRSIRSIRSIES A-Stone Avg, lOton, Min. 7 ton B-Stone 50% >6000#, min.4000# C-Stone 4000# to 4" 50% > 5008 Figure 30. Quadripod rubble-mound jetty (U.S. Army, Corps of Engineers, CERC, 1977). 155 Baie Comeau, Quebec, Canada (August 1962) oy ex 60'- 0" —_— anes . 2 '-0" Compactad crushed stone fe 5'-6" 2 Max. size 4-34" Fiber conduits Steel grating air relief hole Fat ome Secs ; Fresh water |. 4 4 Air relief holes|- pipe I'-0" Wall > : pt otel te: Wave Chamber } Quarry Run Fill size 6" to 12" 3'-0" © Holes, |" chamfer all around Kk 7-4" ++ 7-4 4 7'- 2 | 4-8" - 7 Lee 0 - Figure 31. Perforated caisson breakwater (U.S. Army, Corps of Engineers, CERC, 1977). 156 The unit weight of concrete containing normal aggregates will range from 22.0 to 24.3 kilonewtons per cubic meter (140 to 155 pounds per cubic foot) but can be increased with the use of heavy aggregate to 28.3 (180 pounds per cubic foot) usually at some additional cost. The technique of placement and the size of the armor unit will determine if reinforcing is required in dolas or tribar units. Heavy units, exceeding about 178 kilo- newtons (20 tons) will require reinforcing if placed from a landside unit. Placing armor units from floating equipment where the wave action may cause bumping of the units may require reinforcing in armor units as light as 89 kilonewtons (10 tons). Table 23 lists the concrete armor units in use today and shows where and when the unit was developed. Table 24 lists projects using tetrapods, tribars, quadripods, and dolosse in the United States. Com- monly used types of units are illustrated in Figure 32. e. Other Structures. Concrete has been adopted to many kinds of marine structures as monolithic or cast-in-place structures as well as precast or prestressed units. Concrete is an optimum material for marine structures as it combines durability, strength, and economy. The ability to produce concrete in most any geometric form gives it a high adaptability to most any location and condition of use required. (1) Navigation Structures. Prestressed concrete piles are used for navigation light standards. Navigation aids located on breakwaters, along the shoreline as lighthouses and radio signal towers are usually of concrete construction. Also included as navigation structures are mooring anchors for bouys of all kinds. ; (2) Piers and Wharves. Concrete is the most used construction material in building piers and wharves located either on the coastline or in protected harbors. All the elements of pier construction such as piles, dock units, pier girders, substructures, or bulkheads are built of concrete or a combination of concrete and wood or steel. Even then concrete may be used to protect the wood or steel from erosion, corrosion, dryrot, or marine organisms attack. Figures 33 to 36 are examples of commercial concrete structures located on the coastline. Special piers have been constructed for product loading lines, waste water disposal, and other discharge lines. Figure 37 shows the piling and deck structure of a recreation pier extending from shore to the open ocean. There are, of course, innumerable concrete piers and wharves constructed in bays and protected harbors along the world's shoreline. The use of concrete in these structures is most feasible because it is durable, is readily available in most locations, can be pro- duced in virtually any size or shape, and is economical. Recent developments in precast and prestressed concrete units provide a means of fast and simplified construction procedures with the final structure being both stable and durable. Concrete piling is easily manufactured in most any length to about 36 meters (118 feet), although longer piles have been made and commonly in round, square, octagonal or hollow core cross sections. Either reinforced or prestressed concrete piles can be designed to support very heavy loads. FON, Table 23. Typical concrete armor units in use today. Name of Unit Development of Unit Accropode France Antifer Netherlands Cubel > 2 - Cube (modified)1 United States Dolos! South Africa Handbar Australia Hexapod! United States Quadripod? United States Rectangular Block!,? Stabit England Tetrahedron (perforated)!,3 United States Tetrapod France Tribar! United States IThe units have been tested, some extensively, at the Waterways Experiment Station (WES). 2Cubes and rectangular blocks are known to have been used in masonry-type breakwaters since early Roman times, and in rubble- mound breakwaters during the last two centuries. The cube was tested at WES as early as 1943. 3Solid tetrahedrons are known to have been used in hydraulic works for many years. This unit was tested at WES in 1959. Table 24. Concrete armor projects in the United States. Crescent City, Calif. Breakwater 25-ton tetrapods Kahului, Hawaii Breakwater 33-ton tetrapods Nawiliwili, Hawaii Breakwater 18-ton tribars Rincon Island, Calif. Revetment 31-ton tetrapods Kahului, Hawaii Breakwater 19- to 50-ton tribars Santa Cruz, Calif. Breakwater 28-ton quadripods Ventura, Calif. Jetty 10.7-ton tribars Diablo Canyon, Calif. Breakwater 21.5- to 36.5-ton tribars Humboldt Bay, Calif. Jetty 42- to 43-ton dolosse Crescent City, Calif. Breakwater 40-ton dolosse Cleveland Harbor, Ohio Breakwater 2-ton dolosse Manasquan Inlet, N.J. Jetty 16-ton dolosse 158 Bottom Bottom QUADRIPOD TETRAPOD Elevation oe DOLOS Se (DOLOSSE, plural) A TRIBAR Elevation Elevation Figure 32. Concrete armor units (U.S. Army, Corps of EngaineerSemCERG eS ia) ir 159 "(Seti T1oyiny 310g JO UOTJETSOSSY UPOTIOUy Fo Vy a e. aL 7 Aseqinod ojoyd) nzog “ORBLE FO ai” CS asieg ee oinsty 160 161 tal Shelf off Brazil (photo courtesy of AAPA). inen land on Cont IES eal 5 Artif Figure 34, ‘(vavv Jo Aseqanos ojoyd) evAqrT ‘e8org [Td eSteW 3e ieee So SUTLOOW qutod e[3UrS peXxTty “Gg oansty 162 aa sk Bio Me aS . : See = Figure 36. Port Lotta, Tasmania, ore terminal (photo courtesy of AAPA). 163 = é Figure 37. Hermosa Beach recreation pier. These piles may vary in cross section from 0.15-meter (6 inch) diameter round piles to 0.76-meter (30 inch) solid square or octagonal piles and 1.2 mete: (4 foot) round hollow piles. Hollow piles usually have a 0.15- to 0.30 meter wall. The restrictions on concrete pile size are determined by the equipment required to manufacture them, e.g. the pile bed, forms and, if required, prestressing equipment as well as the pile handling equipment such as cranes, barges and piledriver. (3) Submerged Structures. Concrete is an ideal material for the construction of submerged structures. It may be used for monolithic submerged structures such as structural elements of bridges or precast- prestressed for pipelines, intake and outfall structures, and bridge piers. Other submerged structures usually built of concrete include tunnels for vehicular and railroad traffic and utilities. (4) Floating Structures. Many concrete pontoons of various shapes and size have been constructed as parts of pontoon bridges, quays, wharves, and floating facilities for small boats and seaplanes. Floating breakwaters of precast reinforced concrete pontoons have been installed in Tenakee Springs, Sitka, and Ketchikan, Alaska, and Blaine, Everett, and Port Orchard, Washington. Other structures such as skiffs, launches, scows, barges, floating drydocks, and permanent offshore structures have been constructed of concrete. The construction of fixed breakwaters by floating precast units into place is not uncommon. Caisson units are constructed on a land site, floated into position, sometimes thousands of miles from the construction site, then submerged on the ocean bottom and filled with sand or dredge material. Most any type of floating or sub- mersible structures, at one time or another has been built of concrete. 164 (5) Access and Roadway Structures. Concrete is used for roadways, bridges, structural anchors, and foundations as a part of coastal struc- tures. Overpasses, footbridges, drainage facilities, and concrete pipe are also ancilliary to many coastal structures. (6) Ocean Qutfall and Discharge Structures. Because of the excellent durability of concrete in the coastal environment, many ocean outfall and discharge structures in the coastal zone are made of concrete. These structures accommodate rain and flood water runoff as well as indus- trial and domestic wastes. Ancilliary facilities, such as settling ponds and pumping plants required to make these systems work are also frequently constructed of concrete. 165 VI. OTHER TYPES OF CONCRETE AND GROUT 1. Bituminous Concrete. Asphalt is a primary ingredient of all bituminous concretes. It is a natural constituent of many petroleums in which it ‘exists in solution. If the solvent oils are removed by evaporation or distillation from crude petroleum, an asphalt residue remains. Asphalt is a cement, readily adhesive, highly waterproof, and durable. It is a plastic substance and imparts controllable flexibility to mixtures of mineral aggregates with which it is usually combined. The three general catagories of bituminous concrete used in coastal structures are: asphalt concrete, a mixture of asphalt cement and both fine and coarse aggregate, placed and compacted to form a monolithic structure; sand asphalt, essentially a type of asphalt concrete with coarse aggregate omitted; and asphalt mastic, basically a sand asphalt having a sufficiently fluid consistency during placement to allow it to flow into voids of a rock structure such as a breakwater or jetty. a. Types of Asphaltic Materials. The following terms relating to asphalt are taken from "Asphalt in Hydraulics" (The Asphalt Institute, 1976): "(1) Asphalt Cement. Asphalt that is refined to meet specifica- tions for paving, industrial, or special purposes. (2) Asphalt Concrete, Hydraulic Type. Similar to asphalt concrete for roadway paving, except, to ensure an essentially void- less mix after compaction, higher mineral filler and asphalt contents are used. (3) Asphalt Facing. An asphalt surface designed to resist erosion, abrasion, water pressure, and in some instances, ice pressure. A facing may, in addition, also act as an impermeable layer to prevent leakage through the structure. It may also be termed an asphalt lining or asphalt revetment (see below). (4) Asphalt Grout. A mixture of asphalt, sand, and mineral filler which, when heated and mixed, will flow into place without mechanical manipulation. It is used to bind together a layer of coarse stone of more or less uniform size. It may also be termed asphalt mastic (see below). (5) Asphalt Injection. A pressurized subsurface application of asphaltic material. Usually, injections are made for the purpose of filling subsurface cavities or crevices in the founda- tion soil, or voids beneath an existing pavement layer, primarily for controlling water seepage. (6) Asphalt Lining. That part of a hydraulic structure that functions as a durable, erosion-resistant surface. Usually, its 166 most important function is as a waterproof barrier holding water or other liquid inside the structure. (7) Asphalt Mastic. A mixture of mineral aggregate, mineral filler and asphalt in such proportions that the mix can be applied hot by pouring or by mechanical manipulation; it forms a voidless mass without being compacted. (8) Asphalt Mattress, Slab. Terms, according to size, denoting prefabricated flexible units composed of an asphalt mastic mixture reinforced with mesh, netting, lines, or cables as required. (9) Asphalt Membrane. A relatively thin layer of asphalt formed by spraying a high-viscosity, high softening point asphalt cement in two or more applications over the surface to be covered. It is normally about 6 millimeters (1/4 inch) thick and is used for water- proofing or sealing. It is buried to protect it from weathering and physical damage. (10) Asphalt Mat. A felt or fabric sheet impregnated or coated with asphalt to form a watertight lining or membrane usually 6 millimeters or less in thickness. It may be a sheet that is first installed in place with the asphalt applied following installation, or it may be a finished material that is watertight and ready for installation. (11) Asphalt Revetment. A protective asphalt facing on a sloped surface, usually placed for the purpose of protecting an embankment from erosion. Revetments may or may not extend all the way to either the toe or crest of the sloped embankment. The term subaqueous refers to that part of a revetment placed under the surface of the water. Upper bank paving is that part placed above the surface of the water. (12) Impermeable Asphalt Mixes. Asphalt mixes having low voids, (usually less than 4 percent) after installation, designed to prevent the passage of water. (13) Porous Asphalt Mixes. Asphalt mixes that permit the free flow of water through the mix. Porous asphalt mixes are divided into two general classifications: permeable asphalt mixes and open-graded asphalt mixes (see below). (14) Permeable Asphalt Mixes. Asphalt mixes having medium voids after installation, designed to permit the free passage of water through the lining to and from the supporting layer or embankment. (15) Open-Graded Asphalt Mixes. Asphalt mixes having high voids, designed to provide a free drainage layer underneath an impermeable lining. 167 (16) Prefabricated Asphalt Panels. A layer of a very dense mixture of asphalt and filler sandwiched between two layers of some tough, asphalt-impregnated material and usually coated with water- proofing asphalt." b. Properties of Asphalt Materials. Asphalt has many properties that make it particularly suitable for use in hydraulic and costal zone structures. It is versatile in form and application. Asphalt can be used alone (as in an asphalt membrane), or it can be mixed with other materials producing mixes for a variety of purposes. It can be combined with graded aggregate to form a voidless and impermeable mix. On the other hand, it can be combined with an open-graded aggregate to form a porous mixture allowing free passage of water. Asphalt is stable in the presence of nearly all chemically-laden sub- stances. It is normally unaffected by the usual concentrations of acid, salt, and other waste solutions. This important characteristic makes it useful for waterproofing reservoirs. However, since asphalt is refined from petroleum, other petroleum-based products (which are solvents of asphalt) cannot be stored in asphalt-lined structures. An important property of asphalt is its flexibility. This allows asphalt structures to conform to slight irregularities in the subgrade, and to adjust to small differential settlements that inevitably occur after the completion of a structure. The physical properties of asphalt mixes generally depend on stress conditions and temperature. The ingredients that comprise asphalt mixes have completely different characteristics. The mineral aggregate that makes up the major part of the mix is mainly elastic. The asphalt part, on the other hand, behaves as a viscous liquid at high temperature and under impact load; consequently, asphalt mixtures have both plastic and elastic properties. For many years asphalt cement has been graded on the basis of the pene- tration test, an empirical measures of consistency. Recently, however, the penetration grading of asphalt cements has been replaced by the more funda- mental viscosity grading. Two systems of viscosity grading are currently used. The AC system is based on the viscosity of the original asphalt cement. The AR system, used mostly on the Pacific coast of the United States, is based on the viscosity of the residue of the asphalt cement after it has been subjected to hardening conditions approximating those occurring in normal hot-mix plant operations. The relationships between the various grading systems are shown in Figure 38. c. Asphalt Mixes. (1) Objectives of Asphalt Mix Design. The design of asphalt mixes, as with other engineering materials designs, is largely a matter of selecting and proportioning materials to obtain the desired properties in the finished construction. The overall objective for the design of asphalt mixes is to determine an economical blend and gradation of aggregates 168 “(soeperis Jy TOF onptset--[OAL--3S0} UusAO WITF uTYyy ‘soepeis uotieijoued pue sapeid yy IOF onptset--JOALY --2S9] USAO WTTF UTYI BUT[[OI uo paseq) juouas ypeydse JO Sapeis ALISOISTA pue apeirs uotiet}JOUed Jo uostaeduoy) “gg oan3ty S Ot | -uy : os 08 | -uv O2-9V ool o9! | -uy a (201 X SHSIOd) OT X S-td ‘ANGISHY LOALY "0,09 ALISOOSIA 169 (within the limits of the project specifications) and asphalt that yields a mix having: (a) Sufficient asphalt to ensure durability; (b) sufficient mix stability to satisfy the demands of designed use without distortion or displacement; (c) sufficient voids in the total compacted mix to allow for a slight amount of additional compaction under loading without flushing, bleeding, and loss of stability, yet low enough to keep out harmful air and moisture; and (d) sufficient workability to permit efficient placement of the mix without segregation. (2) Evaluation and Adjustment of Mix Designs. Often, in the process of developing a specific mix design, it is necessary to make several trial mixes to find one that meets the criteria of the design method used. Each trial mix design, therefore, serves as a guide for evaluating and adjusting the trials that follow. For preliminary or exploratory mix designs it is advisable to start with an aggregate of a gradation that approaches the median of the specification limits. Initial trial mixes for establishing the job-mix formula, however, must have an aggregate gradation within the specification limits that the central mixing plant is producing or is capable of producing. Where the initial trial mixes fail to meet the design criteria it will be necessary to modify or, in some cases, redesign the mix. Adjustments in the grading of the original aggregate blend will be required to correct the deficiency. For many engineering materials, the strength of the material frequently is thought of as denoting quality; however, this is not necessarily the case for hot-mixed asphalt paving. Extremely high stability is often obtained at the expense of lowered durability, and vice versa. Therefore, in evaluating and adjusting mix designs always keep in mind that the aggregate gradation and asphalt content in the final mix design must strike a favorable balance between the stability and durability requirements for the use intended. Moreover, the mix must be produced as a practical and economical construction operation. Grading curves are helpful in making necessary adjustments in mix designs. For example, curves determined from the Fuller equation, a version of the maximum density equation using the power 0.5, represent maximum density and minimum voids in mineral aggregate (VMA) conditions. The Fuller equation is: p = 100(d/D)°° where p is the total percentage passing given sieve, d the size of sieve opening, and D the largest size (sieve opening) in gradation. Mixtures described by such curves tend to be workable and readily compacted. 170 SQUARE OPENINGS ee i he 1% SIEVE NO. VV serena ea Vp ee Ly, - AAA LID/QVEIE VAIS G8 /A eel, %” hh" 7 "Pile ‘ : : : iT aps a i PSs = . 100 90 80 CHEE S] > N N = = Ave) = maare (EGAN) GND SNARE VAAFAVRGAGD, YJ Ve a > — eA > eae Hf LH 100 90 80 teal ad oa a uni NU 5 INT ENV GAME S277 ae 7 /| TOTAL PERCENT PASSIN NX N) NN NNN NUNES NNN i “ps oe tf 2 R RE : SPree : TOTAL LaeRenwn BssiKe 171 3 INCHES 2 004 006 .008.0) (LOG SCALE) 92 U.S. STANDARD SIEVES—ASTM DESIGNATION E 11 g grading 1979}. Fuller maximum density curves on standard semilo chart {American Concrete Institute (AGI Figure 39, However, their void contents may be too low. Usually, deviations from these curves will result in lower densities and higher VMA. The extent of change in density and VMA depends on the amount of adjustment in fine or coarse aggregate. Figure 39 illustrates a series of Fuller maximum density curves plotted on a conventional semilog grading chart. Figure 40 illustrates maximum density curves determined from the maximum density equation raised to the 0.45 power {p = 100(d/D)***} and plotted on the Federal Highway Administration grading chart (based on a scale raising sieve openings to the 0.45 power), which many designers find convenient to use for adjusting aggregate gradings. The curves on this chart, however, need not be determined from the maximum density equation. They may be obtained by drawing a straight line from the origin at the lower left of the chart to the desired nominal maximum particle size at the top. For processed aggregate, the nominal maximum particle size is the largest sieve size listed in the applicable specification upon which any material is permitted to be retained. Gradings that closely approach this straight line usually must be adjusted away from it within acceptable limits to increase the VMA values. This allows enough asphalt to be used to obtain maximum durability without the mixture flushing. FEDERAL HIGHWAY ADMINISTRATION 0.45 POWER GRADATION CHART SIEVE SIZES RAISED TO 045 POWER BB 44 it Hii ONISSVd IN3983d i = on cee == (Sse pens pease Se Te | a ae (aes = eule= _— oL_L—_l_] ae] 100 % 4 20 10 Yai SIEVE SIZES inn C55, ein vein Figure 40. Maximum density curves on Federal Highway Administration 0.45 power gradation chart (Federal Highway Administration, 1975). 172 The following is a general guide for adjusting the trial mix, but the suggestions outlined may not necessarily apply in all cases. (a) Voids Low, Stability Low. Voids may be increased in a number of ways. As a general approach to obtaining higher voids in the mineral aggregate (and therefore providing sufficient void space for an adequate amount of asphalt and air voids) the aggregate grading should be adjusted by adding more coarse or more fine aggregate. If the asphalt content is higher than normal and the excess is not required to replace that absorbed by the aggregate, the asphalt content may be lowered to increase the voids. It must be remembered, however, that lowering the asphalt content increases the void content and reduces the film thickness, which decreases the durability of the pavement. Too great a reduction in film thickness also may lead to brittleness, accelerated oxidation, and increased permeability. If the above adjustments do not produce a stable mix, the aggregate may have to be changed. It usually is possible to improve the stability and increase the aggregate void content of the mix by increasing the amount of crushed materials. With some aggregates, however, the freshly fractured faces are as smooth as the waterworn faces and an appreciable increase in stability is not possible. This is generally true of quartz or similar rock types. (b) Voids Low, Stability Satisfactory. Low void content may result in instability or flushing after the mix has been exposed to design loads for a period of time because of reorientation of particles and addi- tional compaction. It also may result in insufficient void space for the amount of asphalt required for high durability, even though stability is satisfactory. Degradation of the aggregate under the action of use may also lead to instability and flushing if the void content of the mix is not suf- ficient. For these reasons, mixes low in voids should be adjusted by one of the methods given above, even though the stability appears satisfactory. (c) Voids Satisfactory, Stability Low. Low stability when voids and aggregate grading are satisfactory may indicate some deficiencies in the aggregate. Consideration should be given to improving the quality as discussed above. ~~(d) Voids High, Stability Satisfactory. High voids are fre- quently, although not always, associated with high permeability. High permeability by permitting circulation of air and water through the asphalt cement may lead to premature hardening of the asphalt. Even though stabili- ties are satisfactory, adjustments should be made to reduce the voids. This usually may be accomplished by increasing the mineral dust content of the mix. In some cases, however, it may be necessary to select or combine aggregates to more closely approximate the gradation of a maximum density grading curve. (e) Voids High, Stability Low. Two steps may be necessary when the voids are high and the stability is low. First the voids are adjusted by the methods discussed above. If this adjustment does not also improve the stability, the second step should be an improvement of aggregate quality as discussed above. 173 (3) Aggregate Gradations and Fractions. For the purpose of speci- fications and test. reporting it is almost universal practice to specify the gradation of aggregates on the basis of the total aggregate gradation, i.e., total percent by weight passing the designated sieve sizes. The individual fractions of the total aggregate gradation, however, are desig- nated as follows: (a) Coarse aggregate (retained No. 8 sieve); (b) fine aggregate (passing No. 8 sieve); and (c) mineral dust (passing No. 200 sieve). It is also important to note that the aggregate gradations as well as the individual fractions are specified independently of the total mix; l.e., the total aggregate equals 100 percent. Aggregate materials often are identified in broader terms as: rock, sand, and filler. These terms usually are applied to the stockpiled materials supplied to the job site. The following definitions appear to have the greatest usage: (a) Rock: material that is predominantly coarse aggregate (retained No. 8); (b) sand: material that is predominantly fine aggregate (passing No. 8); and (c) filler: material that is predominantly mineral dust (passing No. 200). d. Functions in Coastal Structures. (1) General. Asphalt has many properties that make it particularly suitable for use in hydraulic structures. It is versatile in form and application. Asphalt can be used alone (as in an asphalt membrane), or it can be mixed with other materials producing mixes for a variety of purposes. It can be combined with graded aggregate to form a voidless and impermeable mix, or it can be combined with an open-graded aggregate to form a porous mixture allowing free passage of water. There are many types of asphaltic materials used in hydraulic applica- tions. Each type can be classified in one of the following distinct categories: (a) Impermeable asphalt mixes, (b) porous asphalt mixes, (c) asphalt mastics, (d) asphalt cement, and (e) prefabricated asphalt materials. 174 These materials can be used in various forms to waterproof, protect, or rein- force a structure. Table 25 shows how each type of asphalt material may be used to perform these various functions. (2) Impermeable Asphalt Concrete Linings. Impermeable asphalt mixes are similar to asphalt mixes for highway paving except that, since a low void content mix is required to ensure impermeability, they usually have higher mineral filler and asphalt-cement contents. Also a harder, or more viscous, grade of asphalt cement normally is used. Mixes are prepared in an asphalt mixing plant and placed with conventional, or as shown in Figure 41, special paving equipment. Compaction during paving is necessary to produce the required impermeability. ee Figure 41. Roller operated by a dragline compacts the asphalt revetment, San Joaquin River, California (photo courtesy of ACI). The primary purpose of impermeable asphalt mixes is to waterproof hydraulic structures. Watertight linings are used to impound water in reservoirs, ponds, and lagoons; to waterproof dams, dikes, and embankments; and to prevent seepage losses in canals and channels. They are most often used as surface linings, since they are resistant to wave action and the erosive effects of water currents. Revetments constructed with impermeable asphalt mixes are used for bank protection on streams, reservoirs, lakes, and shorelines. Waterproofing 175 S2uUsUAeIIA uofyer{ouIYg *Zurqno1y S$2usu2 e282} uo} IBIQIUeg *Zuzano1ry San *sodnjzoni4s IT[TNeipAy TOF STetso}zeEw ot yPeydse Jo suotqzeot{ddy ‘sz 9TqeL sqets ‘sassaiqIeEW ‘sTourg $3809 [ees *‘s2uyut. asoejans saohe{ o8eupeip aoejansqns pepeaz-uedo *sZuzutT avejains eT qrewisg S3upUTT pesodxe 20 32eziNns me te uoz zoung SqPTS SsassaiqiqeEW *sqa0us *sToueg suofjoofuT aanssead aoezansqns s}e0D [Tess *souraquay uoFAo.efuy voezansqns *sai0d weg *SsTTem yyoqng *sjeod [eas *s2uTUTT s0ejains S3uyUtT pasodxs 20 aoesans | ween s[TefieqeW 3apteudsy pe yeofaqejeig juawe) 3aTeydsy SOPFISEY 3Teudsy sox aTeydsy sno10g sextW ateudsy aTqeewzeduy fe 176 _ properties are not necessarily required in these instances, but quality asphalt concrete linings having low voids effectively resist the destructive effects of wave and current action as well as their abrasive effects (Figs. 42 and 43). Impermeable asphalt mixes may be used for the entire lining of the structure. They may also constitute a part of a more complex lining. They can, for example, be placed as the surface of a composite section made up of different asphalt layers. (3) Porous Hot-Mix Asphalt Linings. Porous asphalt mixes for hydraulic structures are characterized by the absence or reduced amount of fine aggregate or sand in the mix. As a consequence, the asphalt content is also reduced. The mixes have interconnected pores that permit passage of water. A harder, or more viscous, grade of asphalt cement is desirable in these mixes to allow sufficient film thickness and to prevent drainage from the aggregate. This choice of asphalt also provides additional cohesion in the mix between the aggregate particles. There are two types of porous asphalt linings: permeable and open- graded. Permeable hot-mix asphalt linings serve as a cover over an earth embankment to protect it from erosion by wave action or surface runoff. Open-graded asphalt linings, with higher void content than the permeable lining, serve as drainage layers under an impermeable lining while at the same time contributing to the structural strength of the lining. In either case, the purpose is to provide free drainage to prevent hydrostatic pressures from building up in the embankment or within the lining itself. Asphalt, as a surface lining, allows water to flow to and from the embankment through the lining. As a drainage layer, asphalt collects the subsurface water, channeling it to drains for removal. (4) Asphalt Mastic Mixes. Asphalt mastic mixes for hydraulic structures are essentially mixtures of mineral aggregate and filler where the voids in the mineral matrix are overfilled with asphalt cement. The result is an asphalt mix that can be applied by pouring or by hand-floating into place. Asphalt mixes require little or no compaction after placing because void spaces in the aggregate matrix are filled or slightly over- filled with asphalt. Asphalt mastics may be made from a variety of aggre- gate materials ranging from well-graded coarse and fine aggregates and mineral filler to essentially mineral filler alone with or without an additive such as asbestos fibers. The mastic is voidless except for air bubbles that may be trapped during the manufacture and placing. Asphalt mastics can be used in several ways to waterproof, protect, or reinforce a hydraulic structure. For waterproofing, asphalt mastics have been used for cutoff walls for dams as well as for the central core of the dam itself. They are also used as exposed watertight surface linings. Asphalt mastic mixes are erosion-resistant; therefore, they can be exposed to waves and abrasive water action. They are also used to form protective covers on embankments or over the floor of channels or estuaries that are subject to erosion. Hot mastic mixes can be placed underwater through tremies, chutes, or by simply dumping in masses. They are also used for constructing flexible slabs or mattresses that are lifted into place to form a protective blanket or cover. 177 10 - 15cm (4-6 in.) ASPHALT CONCRETE HEIGHT STORM WAVE CREST 20 - 30cm (8 - 12 in.) ASPHALT CONCRETE MEAN HIGH WATER HEAVY RIPRAP, ASPHALT GROUTED MEAN LOW a Figure 42. Seawall slope revetment. Placing mix by spreader box. Figure 43. 178 For reinforcing, asphalt mastics are used as grouts to fill and plug the voids in stone structures such as jetties and revyetments (Figs. 44 and 45). The binding action of the mastic tends to make one firm mass, yet mastics are flexible enough to conform to some differential settlement in the structure. Asphalt mastics are also used as joint fillers to bind stone blocks together on coastal structures, particularly in European construc- tion. 2.4 m (8 ft) ASPHALT CONCRETE CAP ASPHALT SEAL (GROUTING) COURSE COVER STONE 5.4 to 9.1t (6 TO 10 TONS) CORE STONE 34kg to 1.8t 0.9 m (3 ft) RIPRAP 7 to 91 kg (15 to 200 LB.) Figure 44. Cross section, south jetty, Galveston, Texas. (S) Surface Treatments. (a) Purposes. A surface treatment may be applied to an asphalt surface for a number of reasons. It may be designed to make the surface more watertight, or to protect it from abrasion by waves, water currents, or even by ice. A layer of mud deposited on an asphalt surface or algae and other sediments, and allowed to dry, will shrink as they dry will set up suprisingly large tensile stresses at the surface resulting in the surface curling or cracking. A surface treatment may also be used to protect the surface from mud curl or the curling of drying algae along the waterline, to give the surface a lighter color in order to reduce tempera- ture extremes, or to reduce the rate of oxidation of the exposed asphalt surface. (b) Sprayed Asphalt Seals. Asphalt cement or emulsified asphalt sprayed over the surface of an asphalt lining at the rate of 1 liter per square meter (0.25 gallon per square yard) will provide a film coating as much as 1 millimeter (0.04 inch) thick. A continuous film coating will fill and seal any exposed pores and increase the watertightness of the asphalt lining. It will also tend to fill and seal small cracks in the surface that may have been caused by improper rolling procedures in compacting the lining. The surface should be clean, dry, and free from 179 *(93n3TIsSUul ATeydsy Fo Asoqanos oyoyd) Teas ate ydse yitm AqW0f UOJSSATED “Sp omn3Ty a - ee 180 loose material. Its temperature should preferable exceed 38° Celsius (100° Fahrenheit). A sloped surface usually necessitates hand spraying. This should be done in a back-and-forth sweeping motion to build up the film and to keep the asphalt from flowing down the slope. (c) Asphalt Mastic Seals. In addition to providing a seal, asphalt mastics applied to the surface of asphalt linings provide protection from mechanical abuse. Asphalt mastics, generally placed on an asphalt lining with a screed, permit a heavier coating than sprayed applications, and well-designed mixtures can make the surface resistant to abrasion by waves, or scouring by waterborne sands. Asphalt mastic mixtures for this purpose are essentially blends of mineral filler and asphalt cement. (d) Prefabricated Asphalt Panels. The typical prefabricated asphalt panel consists of a core of ductile, blown or oxidized asphalt (asphalt which has certain natural characteristics changed by blowing air through it at elevated temperature) fortified with mineral fillers and reinforcing fibers. The ingredients are blended and molded under heat and pressure. The core is then sandwiched between protective sheets and a protective coating of hot-applied asphalt cement. The protective sheets may be an asphalt-impregnated felt, or plasticized or flexible glass fabrics (Fig. 46). Figure 46. Lining ditch with prefabricated asphalt panels. Asphalt panels are usually about 13 millimeters (1/2 inch) thick, but they are available as thin as 3 millimeters (1/8 inch) thick. They are usually 1.0 to 1.2 meters (3 or 4 feet) wide and 3 to 6 meters (10 to 20 feet) long for handling and placing. 181 The most extensive use of prefabricated asphalt panels has been in lining and waterproofing all types of water storage reservoirs, including domestic water reservoirs, sewage lagoons, industrial waste-treatment reservoirs, evaporation ponds, and reflecting pools. They are also used for lining canals and ditches, and for bank protection. Prefabricated asphalt panels have been used underneath riprap or rock reveted embankments to prevent leaching of sand and earth through the rock revetment usually caused by action of waves and tides. The development of geotechnical fabrics has largely replaced the use of asphalt panels in recent years. Asphalt panels have the advantage of providing a relatively thin watertight barrier that can be used as a surface lining. In addition, they do not require heavy machinery to install. They are useful for relining reservoirs where the concrete lining has cracked badly and where leaking has been excessive. Prefabricated asphalt panel linings are also used as an element of composite lining structures, most frequently serving as the watertight surface of a built-up lining. (6) Miscellaneous. (a) Sand Asphalt. Sand asphalt is a mixture of sand, with or without added mineral filler, and asphalt cement. Mineral filler added to the mix permits a higher asphalt content and makes it possible to obtain a denser, tougher, and more stable mix. Sand asphalt has been used alone for linings, as base courses for other linings, for revetments, and for groins, although not in the coastal zone. The largest use of sand asphalt for hydraulics purposes in the United States probably has been for bank paving along the Mississippi River by the U.S. Army Corps of Engineers. The Netherlands has made extensive use of sand asphalt in the construction of seawall revetments. Typically, the base thicknesses range up to 0.20 meter (8 inches) and are usually capped with a layer of asphalt concrete. Local sand deposits generally can be used, as gradation is not par- ticularly critical. The asphalt cement should be AC-20 (or equivalent AR- or penetration grade) or a higher viscosity grade. A typical mix would have an asphalt content of about 6 percent. If about 5 percent mineral filler is added, the asphalt content would probably be around 8 percent. Sand asphalt mixes for linings are not as watertight as specially designed hydraulic asphalt concrete. (b) Asphalt Prime Treatments. Priming the soil surface of a hydraulic structure with asphalt is often done to seal it temporarily or to reduce seepage until such time as waterborne sediments in the impounded water settle and plug the soil pores. Asphalt primers have also been applied to sloped embankments before placing a sprayed-asphalt membrane. The purpose, in this case, is to anchor the membrane to the slope. Primes have also been used for much the same purpose as prime treatments of roadway surfaces prior to paving operations, that is,to plug up voids and to provide a more stable surface on which to place asphalt construction. Prime treat- ments are neither watertight nor permanent. They are most applicable to silty sand soils that are quite permeable. 182 (c) Asphalt Injection. Asphalt injection is the subsurface application of asphalt pumped under pressure through pipes. The method is used to reduce leakage of a hydraulic structure through underground cracks, fissures, and cavities. Injection of asphalt into the subsurface has been done to prevent leaching of soils through rock reveted embankments at commercially developed sites to prevent surface subsidence behind the embankment. The hot, fluid asphalt is usually pumped through heated perforated pipes dropped into drilled holes at the leakage strata levels. Once in the leakage channel, the asphalt spreads out and hardens into a tight plug or water stop. With sufficient pumping pressure, the asphalt will do this even in fissures filled with water. These asphalt plugs can adapt to slight movements in the formation and changes in water pressure. (d) Asphalt Mattresses. Asphalt mattresses are precast sections or blankets of asphalt mastic reinforced with wire mesh and steel cables or fiber netting and lines. Generally they vary in thickness from 25 to 50 millimeters (1 to 2 inches). Their length and width are limited only by the size of the molding platform and the cababilities of the equipment used to manipulate and place them. The reinforced asphalt mattress was developed by the U.S. Army Corps of Engineers in 1932-34 for use on underwater revetments on the banks of the lower Mississippi River. Continuous asphalt mattresses were cast on a special barge pulled into the water. Mattresses have since been adapted for use in European hydraulic structures and in Japan. Their principal function is to protect the surface on which they rest from erosion or scour by waves and currents. They are often used at the toe of a revetment or lining. After a short period, the edge of the mattress settles into the scour zone, thus stabilizing the erosive process. Asphalt mattresses are also used as linings and as protective blankets for hydraulic structures. 2. Preplaced Aggregate Concrete. Preplaced aggregate (PA) concrete derives its name from the unique placement method by which it is made. Intrusion and grouted concretes are other common names used for this type of concrete. In this method of construction, forms are first filled with clean, well-graded coarse aggre- gate. Structural quality grout is then injected into the voids of the aggregate mass to produce concrete. This method of placing concrete is especially adaptable to underwater construction, to concrete and masonry repairs, and, in general to new structures, where placement by conventional means is unusually difficult or where concrete of low volume change is required (U.S. Bureau of Reclamation, 1963). This method of placing concrete has been used in the construction of bridge piers, atomic reactor shielding, plugs for outlet works in dams and tunnels, in mine workings, and for embedment of penstocks and turbine scroll cases, as well as a great variety of repair work. Recently this process has been used for exposed aggregate and other architectural treatments. Inasmuch as preplaced aggregate concrete construction is a relatively specialized type, it is essential that the work be undertaken by well-qualified personnel, experienced in this method of concrete construction. 183 Preplaced aggregate concrete differs from conventional concrete in that it contains a higher percentage of coarse aggregate in the finished product. Because of point-to-point contact of the coarse aggregate, as placed, drying shrinkage is about one-half the magnitude of that which normally occurs in conventional concrete {U.S. Army Engineer Waterways Experiment Station (WES), 1954; Shideler and Litvin, 1964}. The higher percentage of coarse aggregate in the concrete has an in- fluence on the modulus of elasticity which is slightly higher than that of conventional concrete. The other physical properties also appear to be more affected by the properties of the coarse aggregate than occurs with conven- tional concrete. In summary, the physical properties of preplaced aggregate concrete are similar to those of conventional concrete except that overall drying shrinkage of the former is considerably less. Accordingly, with a properly proportioned and tested grout mix and with good construction practices, allowable working stresses used for conventional concrete struc- tural design may be used (U.S. Army Engineer, WES, 1954). The economics of its use are a function of site conditions and job requirements. Structural forms for the concrete are usually more expensive than that required for conventionally placed concrete because greater care is needed to prevent grout leaks and placements usually require additional lateral support. However, in underwater construction, higher placing rates have been achieved by this method than by conventional placing methods. a. Types of Grouts. Slurries of Portland cement and water, with or without sand, have long been used in the construction industry for filling of rock fissures. Unless sufficient pressure is applied to squeeze out excess water, settlement of solids may result in incomplete filling of voids. Clean sand-cement or soil-cement slurries may be used for low- pressure backfill grouting of rubble or rockfill where strength is not an important consideration. As concrete technology has changed, basic grouts composed of Portland cement, sand and water have been modified to more effectively produce structural preplaced aggregate concrete. Such grouts may be modified chemically by the inclusion of admixtures such as pozzolans, fluidifiers, expansion agents, air-entraining agents, and coloring additives; or the grout may be modified mechanically by use of specially designed high-speed mixers. b. Grout and Aggregate Materials. (1) Cement. Grout can be made with any one of the types of cement that complies with ASTM, Standard C150, Corps of Engineers specification CRD-C 201, which would be suitable for use in conventional concrete and produce the required conditions for preplaced aggregate concrete. The type of cement should be selected in accordance with controlling factors, job conditions, and service exposures which would influence the same selection for conventional concrete. (2) Coarse Aggregate. Coarse aggregate must be clean, free of surface dust and fines, sound, durable, and should conform to ASTM Standard C33, Corps of Engineers specification CRD-C133, for aggregate acceptance, 184 except as to grading. Importantly, the coarse aggregate should not be susceptible to excessive breakage and attrition during handling and placing in the forms. The void content of the coarse aggregate after placement in the form will customarily range between 38 to 48 percent. For economy, it is desirable to keep the void content as low as possible to minimize the required volume of the intruded grout. A low void content not only results in a saving in cementing materials, but, concomitantly, less volume change. The maximum size aggregate depends on availability, type of construction involved, and usual limitations established for thickness of section and spacing of reinforcement bars (King, 1959). The minimum recommended size is dependent, essentially, on sand grading. Typical aggregate gradations are shown in Table 26. When grout is prepared with sand graded for use in conventional concrete, minimum coarse aggregate size should be 38 millimeters (1.5 inches). When a mason or plaster sand grading is used, minimum coarse aggregate size may be reduced to as low as 13 millimeters (0.5 inches). No limit is placed on maximum size of the coarse aggregate. Table 26. Typical aggregate gradations for preplaced aggregate concrete prepared with fine sand grout containing pozzolan and fluidifier Typical fine aggregate grading Cumulative percentage passing given sieve No. 30 No. 50 No. 100 Typical coarse aggregate grading Cumulative percentage passing given sieve in. TWStiny 63/4 ans S/S ins) Seam. Geile (22). Aaa ea GO 0) TMOG) 50 (12.5 mm) - mm ) The coarse aggregate should be well graded up to and including the largest size which can be placed economically in the forms without excessive segregation. Gap grading, using a ratio of minimum nominal size coarse aggregate to the maximum nominal size fine aggregate of 10:1 without inter- mediate sizes, has been occasionally used to achieve exceptionally low void 185 cements. However, this grading is uneconomical for most work. Coarse aggregates as large as the largest stones capable of being carried hy a man have been used with gaod results. (3) Fine Aggregate. Either crushed or natural sand may be used. However, well-rounded sand grains from a natural source are preferable because such sands require less water to achieve acceptable grout fluidity. The sand should be hard, dense, durable, uncoated rock particles, and of a uniform, stable moisture content. It should conform to current ASTM Standard C33, except with respect to grading. (4) Pozzolan. Pozzolan is used to reduce bleeding, to improve fluid properties of the mixture, and to reduce segregation of solid particles. The pozzolan combines with lime liberated during hydration of the cement to form strength producing compounds at later ages. The rate at which pozzolan contributes the heat of hydration is much slower than that of Portland cement. Both natural and manufactured pozzolans have been used, but the pozzolan most generally used and preferred is fly ash conforming to ASTM Standard C618, Corps of Engineers Specification CRD C255. Some pozzolans have caused excessive abrasion of pumping equipment and increased water requirements, so preliminary tests should be made with the selected pozzolan. (5) Grout Admixtures. A water-reducing, set-retarding agent, known as a grout fluidifier, is commonly incorporated in the grout mixture to make it more fluid, to reduce the amount of water otherwise required for a given fluidity, to delay setting time for ease in handling with pumping equipment and to promote better penetration of the voids in the coarse aggregate. This agent is customarily a preblended material obtained commercially. It normally consists of a water-reducing agent, a suspending agent, aluminum powder, and a chemical buffer to assure properly timed reaction of the aluminum powder with alkalies in the cement. Reaction of the aluminum powder with alkalies during hydration of the cement generates hydrogen gas which causes expansion of the grout while it is fluid and provides small air bubbles within the grout. Normal dosage of the water- reducing agent in commercially available grout fluidifiers ranges from 0.20 to 0.30 percent by weight of cement plus pozzolan. Aluminum powder is normally employed in the range of 0.01 to 0.02 percent by weight of cement plus pozzolan. The fluidifier should be so proportioned that most of the expansion occurs within 3 hours after initial mixing. Preblended grout fluidifiers should conform to Corps of Engineers Specification CRD C619. c. Grout Mix Proportioning. Grout material proportions, as in conven- tional concrete practice, are influenced by structural design requirements. Additionally, the grout must be so designed as to flow freely through the voids of the preplaced aggregate without appreciable segregation or water gain so that honeycombing is avoided and an intimate bond between grout and coarse aggregate particles is ensured. The importance of selecting maximum sand size, compatible with void size as determined by coarse aggregate grading, is reflected in Table 26. Cement-to-sand ratios employed are commonly in the range of 1:1 to 1:2; although ratios as lean as 1:3 cement to sand have been used. Compressive strength and pumpability requirements limit the amount of sand which can be used in any grout (U.S. Army Engineer, WES, 1954). The grout must be 186 sufficiently fluid so that it will penetrate and fill all the voids in the aggregate mass, yet be of such consistency that the suspended sand and cementing materials do not settle out. For normal structural work, the ratio of cementitious materials (cement plus pozzolan) to sand should be approximately 1:1. Usually, the proportions of cement to pozzolan are 2:1, although ratios as low as 1:1 and up to 9:1 have been used on various jobs. Occasionally, the pozzolan may be omitted entirely. For a structural grout, it is usually not desirable to exceed a cement to sand ratio of 1:2 by weight because higher ratios produce lower strengths and excessive segregation of sand in the grout mixture may occur. Mix proportions may be determined by Corps of Engineers Specifications CRD Cél5. d. Physical Properties. For structural preplaced aggregate concrete where strength and other physical properties are a consideration, the grout should be proportioned and test specimens, using the contemplated coarse aggregate grading, should be made to determine the grout mix proportions which will produce preplaced aggregate concrete of the required physical properties. Such tests will also provide information as to the quantity of materials needed for the work. Where necessary, the information on physical properties of the structural preplaced aggregate concrete should include strength, resistance to freezing and thawing exposure, modulus of elasticity, drying shrinkage, volume change, or other structural criteria. Physical properties of preplaced aggregate concrete made with a grout containing pozzolan and a fluidifier have been determined and compared with conventional concrete in a number of laboratory tests. This data can be found in pub- lished reports (U.S. Army Engineer, WES, 1954) (U.S. Bureau of Reclamation, 1949). Compressive strength of concrete with a given maximum size aggregate, grout fluidifier, and pozzolan is slightly lower at 28 days' age than that of conventional concrete containing entrained air and an equal amount of cementing materials. At 90 days' age and later, its strength is equivalent to that of conventional air entrained concrete (U.S. Army Engineer, WES, 1954). Concrete containing aluminum powder or a grout fluidifier, and pozzolan develops a higher bond strength with old concrete than does new, conventional concrete. This may be explained because of the greater fluidity of the grout as compared with mortar and the expansion of the grout which develops a slight pressure during the formation of the hydrogen gas. e. Placement. (1) Foundation Preparation. Foundation preparation is important in underwater placement. For example, if extremely fine material is left on the foundation or in heavy suspension just above the foundation, it will be displaced upward into the aggregate. The dispersed fine material then coats the aggregate or settles and becomes concentrated in void spaces in the aggregate, thus precluding proper intrusion and consolidation. Therefore, all loose fine material must be removed insofar as possible before placement of aggregate. Alternatively, if structural conditions permit, a layer of sand and gravel may be first deposited to serve as a filter bed to prevent contamination of preplaced coarse aggregate. (2) Aggregate Placement. Coarse aggregate should be washed and screened immediately before placing in the forms so that it will be surface 187 moist at the time of grout injection. Dry aggregate will absorb water from the grout which thickens the grout within the aggregate mass and may result in ungrouted or honeycombed areas. If more than one size of coarse aggregate is used, the aggregate should be weighed, batched, and mixed in the proper proportions, or discharged at proportional rates onto the wash screen. The wash screen may be either a vibrating deck or revolving type. The latter is effective as a blender, as well as a washer. For structural concrete work, aggregate is commonly conveyed to the forms in concrete buckets. A flexible rubber elephant trunk is often used to limit the height of free fall, thus preventing segregation, and for placing in constricted areas. The total fall distance and method of handling should be such that segregation and aggregate breakage are reduced to a minimum. Permissible fall distance depends on aggregate size and soundness. Where coarse aggregate is being placed through water in mass concrete work, as in bridge piers, it may be discharged directly into the forms from bottom dump barges or self-unloading ships. Coarse aggregate has been placed successfully to depths of well over 30.5 meters (100 feet) in water where the possibility of breakage is eliminated (Davis and Haltenhoff, 1956). While some segregation may occur, segregation itself is not usually objectionable since it tends to result only in a somewhat greater void content and a non-uniform distribution of the void system throughout the aggregate mass, the result being to increase, slightly, the grout require- ments with an insignificant effect on the strength of the mass concrete. However, an accumulation of smaller sizes might reduce the void size suffi- ciently to preclude consolidation within the area by the grout. (3) Grout Quality Control. The pumpability of grout is controlled by the consistency test, using a standard flow cone in accordance with Corps of Engineers CRD C611. To maintain uniformity, time of outflow should be limited to between 18 and 22 seconds. However, grouts can be successfully pumped having an outflow of up to 30 seconds, depending on void content of the aggregate. Test cylinders should be made in accordance with Corps of Engineers Specification CRD C84 and tested in accordance with appropriate ASTM standards. f. Curing. Curing should be in accordance with accepted conventional concrete practice. As with any concrete, extended periods of wet curing beyond the usual 7 days will be beneficial in improving the quality of the concrete. 3. Portland Cement Grout. a. Types and Characteristics. Portland cement grout has a variety of uses in coastal structures and is similarly varied in its makeup. A simple combination of cement and water, in a flowable consistency, is sometimes used to fill joints and yoids in concrete, masonry, or rock. More often other materials are added to improve various properties or reduce cost. These include sand and clay, used as inert fillers, and colloidal clays such as bentonite to stabilize fresh grout placed under water. Also included are special purpose admixtures to increase strength, retard or accelerate set and strength gain, cause expansion of the grout, prevent shrinkage, or improve bond, penetration, impermeability, plasticity, or resistance to freeze-thaw damage or chemical attack. These are discussed more fully in 188 Section V, Portland Cement Concrete, and in the previous discussion of preplaced aggregate concrete. In some cases the desired properties can be satisfactorily obtained by using one of the previously described special types of Portland cement. b. Mixes. Where grout can be pumped or poured into relatively open joints or voids a mixture of one part cement to typically three or four parts sand is common, with just enough water for satisfactory placement. For very large voids, gravel may also be added. Where the material will be pumped into the ground to raise a settled slab or behind a bulkhead to plug a hole or break, a mixture of clay or silt with about 10 percent cement can sometimes be used. For filling or repairing narrow joints or cracks a neat cement grout consisting of 1 part cement mixed with 1 to 10 parts water to obtain proper consistency, may be appropriate. In some cases the use of an admixture may be justified to enhance certain properties. In such a case care should be taken to ensure the suitability of the admixture for the conditions and materials involved, and that dosage and mixing are correct. Pertinent Corps of Engineers Specifications include CRD C615, CRD C619, CRD C611, and CRD C612. c. Placement Methods and Effects. Portland cement grout is usually placed by one of the following methods: (1) Dumping or pouring into large voids or onto flat or sloping surfaces; (2) free discharge from a hose or tremie trunk, above or under water, into a form or into voids or cavities in rock, masonry, or concrete; (3) pressure discharge from a hose or pipe; (a) into soil to correct settlement of a slab or light foundation by displacement or "mud jacking," or behind a bulkhead for sealing or patching; or (b) into cracks or joints in concrete, masonry, or rock; and (4) hand placement by pouring or ''dry packing." Where grout is used to fill joints, cracks or cavities in structural members it will be important to ayoid or minimize shrinkage. This will require the best practicable combination of compaction, low water-cement ratio, and possibly the use of an expanding or plasticizing admixture in the grout. If a significant surface area of freshly placed grout is exposed to the air, especially when the grout has a high cement factor, the surface will need to be kept continuously moist for several days if shrinkage cracks are to be ayoided. If the grout is injected into a confined space, such as immediately behind a bulkhead or into cracks or cavities, caution must be used to avoid building up excessive pressure which could displace or rupture the confining structure. This can be avoided by carefully limiting the injection pressure, 189 or by grouting in properly sized increments or lifts and allowing adequate setting time between them. Tests for the setting time of grout are described in Corps of Engineers Specification CRD-C614. d. Effects of the Environment. Portland cement grout will be affected to varying degrees by the environmental conditions and forces acting on the concrete, masonry or rock with which it is associated. Placed in thin joints or cracks it will have some protection from wave action, abrasion, periodic wetting and drying, and fire but may be vulnerable to water penetration, freeze-thaw cycles, chemical attack and seismic forces. Where used for surface repair, topping or void filling it may be exposed to all these. Most of these environmental forces will be adequately resisted by a grout having an optimum combination of strength, impermeability, entrained air content, and freedom from excessive shrinkage. Where a certain type of exposure is likely to be severe, the added cost of a beneficial proprietary admixture may be warranted. e. Functions in Coastal Structures. The many uses of Portland cement grout can be broadly classified as follows: (1) In protective structures: (a) filling voids in rock revetments; (this may be for improved slope stability, erosion resistance against waves, currents or floating debris, or rat-proofing) ; (b) filling joints in precast block revetments; or (c) sealing voids in stone breakwaters to improve wave attenuation. (This should be undertaken very judiciously, lest it cause excessive pressure buildup in the breakwater structure under heavy wave action, or trap and amplify resonant wave energy within the protected water area). (2) In functional structures: (a) grouting cyclopean or preplaced aggregate concrete; (b) setting steel piling or tieback anchors in rock; and (c) filling voids in hollow masonry walls. (3) In structural repairs: (a) repairing spalled, broken or cracked concrete; (b) plugging breaks or holes in steel or concrete bulk- heads; and (c) correcting foundation settlement. 4. Soil Cement. a. Description of Soil Cement. Soil cement is a mixture of pulverized soil and measured amounts of Portland cement and water, compacted to a high 190 density. As the cement hydrates, the mixture becomes hard and increases the stability of the soil. The term ''soil'' includes native soils, gravels, sands, crushed materials, and miscellaneous materials such as cinders, slag, caliche, and chert. b. Types of Soil Cement. There are three general types of soil cement mixtures depending on the quantity of cement and water added to the soil. (1) Compacted Soil Cement. This mixture contains sufficient cement and moisture for maximum compaction. It will withstand laboratory freeze- thaw tests (ASTM Standard D560, CRD C594) and wet-dry tests (ASTM Standard D559, CRD C593) and will meet weight loss criteria. (2) Cement-Modified Soil. This is an unhardened or semihardened mixture of soil and cement. When relatively small quantities of cement and moisture are added to a soil, the chemical and physical properties of that soil are changed. The soil's plasticity and volume change capacity are reduced and its bearing value increased. In cement-modified soil, only enough cement is used to change the physical properties of the soil to the desired degree--less cement than is required to produce a hard soil-cement. The use of cement to produce a cement-modified soil can be applied to both silt-clay and granular soils to increase the bearing values and reduce plasticity of soil materials. (3) Plastic Soil-Cement. This is a hardened mixture of soil and cement that contains sufficient water, at the time of placing, to produce a consistency similar to that of plastering mortar. Plastic soil-cement is used to line or pave steep or irregular slopes for erosion control of banks and ditches. c. Mixing Soil Cement. Since soil-cement obtains its stability primarily by the hydration of cement and not by cohesion and internal friction of the materials, practically all soils and soil combinations can be hardened with Portland cement. The general suitability of soils for soil-cement can be judged, before they are tested, on the basis of their gradation. On the basis of gradation, soils for soil-cement can be divided into three broad groups. (1) Sandy and Gravelly Soils. Sandy and gravelly soils with about 10 to 35 percent silt and clay have the most favorable characteristics and generally require the least amount of cement for hardening if they contain 55 percent or more passing No. 4 sieve. These soils are readily pulverized, easily mixed, and can be built under a wide range of weather conditions. i (2) Sandy Soils, Deficient in Fines. Soils such as some beach, glacial, and windblown sands make good soil-cement, although the amount of cement needed for adequate hardening may be higher than the first group. (3) Silty and Clayey Soils. These soils make satisfactory soil- cement, but those cantaining high clay contents are harder to pulverize. Generally, the more clayey the soil the higher the cement content required to harden it gradually. 19} Excessivly wet soil is difficult to mix and pulverize. Experience has shown that cement can be mixed with sandy soils when the moisture content is as high as 2 percent above optimum. For clayey soils the moisture content should be below optimum for efficient mixing. d. Curing. Compacted and finished soil-cement contains sufficient moisture for adequate cement hydration. A moisture-retaining cover must be placed over the soil-cement soon after completion to retain this moisture and permit the cement to hydrate. Materials such as waterproof paper or plastic sheets, wet straw or sand, wet burlap or cotton mats are entirely satisfactory. e. Engineering Properties of Soil Cement. During construction the soil-cement 1s compacted to a high density. As the cement hydrates, the mixture hardens in this dense state to produce a structural slablike material, and thus possesses engineering properties. The magnitude of these properties depends primarily on the type of soil, age and curing conditions. Depending on soil type, 7-day compressive strength of saturated speci- mens of the minimum cement content meeting soil-cement criteria is generally higher than 2.1 megapascals (300 pounds per square inch). The 28-day flexural strength is approximately 20 percent of the compressive strength, and the modulus of elasticity about 6 900 megapascals (1 million pounds per square inch). Soil cement tends to be brittle, cracking under impact and temperature stresses. f. Functions of Soil-Cement. Soil-cement is used primarily as a base course for stabilizing and compacting soils for foundations, bank protection and subbase construction. It has been used for earth dam cores, reservoir linings, and slope protection. 5. Sulfur Cement Concrete and Grouts. a. Introduction. The past 15 to 20 years have seen a rapid increase in research and development work on sulfur, and two factors have been the cause of this increase. In the early 1960's, large quantities of sulfur were beginning to be recovered from sour natural gas and petroleum. Sulfur producers realized the necessity of creating new end-use markets to absorb this sulfur, and sponsored research to that purpose. As a result of this research, sulfur was discovered, or in some cases rediscovered, to have a number of interesting mechanical properties. Research workers who originally had envisioned sulfur as a substitute material now discovered that sulfur had properties superior to some conventionally used materials and that it could outperform such material both technologically and economically. These initial discoveries stimulated additional research in many aspects of sulfur. Many interesting new uses for sulfur in construction have been discovered. Some of the more promising are: (1) Sulfur asphalt paving materials, (2) sulfur concretes, (3) sulfur coatings, 192 (4) impregnating materials with sulfur, and (5) foamed sulfur. The acceptance of sulfur asphalt technology by highway departments and contractors has been due not only to the desire to replace asphalt by readily available sulfur, but also to the fact that the sulfur asphalt materials have shown improved properties compared to asphalt, and to the fact that sulfur asphalt permits the use of aggregates which would be unsuitable for use with asphalt. It has been known for many years that mixing molten sulfur with sand or aggregate produces a sulfur concrete with excellent strength. However, the durability of simple sulfur concretes of this type has not been impressive, particularly under conditions of high humidity and wide temperature fluctua- tion. Research has centered on developing additives to sulfur to improve the durability. Work carried out by the U.S. Bureau of Mines at Boulder City, Nevada, and by Sulfur Innovations, Ltd., Calgary, Alberta, has resulted in sulfur concretes with greatly improved properties. Porous materials can be impregnated with molten sulfur that, on solidify- ing, imparts additional strength to the materials. Resistance to freeze- thaw cycles and corrosion is also frequently improved by sulfur impregnation. Recent research indicates that with suitable additives, sulfur could be made into a rigid foam having excellent mechanical and insulating properties. The properties of sulfur-based construction materials generally equal or surpass those of conventional cementing materials. b. Sulfur-Asphalt (SA) Materials. Basically, all the SA technologies involve combining molten sulfur and hot asphalt to produce a sulfur-asphalt binder, which is then mixed with mineral aggregate to give a SA hot-mix paving material. The individual technologies differ in the method and equipment used to produce the SA binder. (1) Mixes. Depending on the technology and type of aggregate used, from 1/3 to 1/2 by weight of the asphalt can be replaced by sulfur. Because sulfur is about twice as heavy as asphalt, sulfur-asphalt binders have higher densities than normal asphalt. Because a certain volume of binder is needed to obtain an acceptable void content of the compacted paving material, optimum stability of SA paving materials generally occurs at a somewhat higher binder content (by weight) than when straight asphalt is used. In practice, between 6.2 and 8.9 newtons (1.4 and 2 pounds) of sulfur are needed to replace 4.4 newtons (1 pound) of asphalt. Because SA paving materials are three-component systems (sulfur-asphalt-aggregate) they permit more flexibility of design than with regular two-component (asphalt-aggregate) paving materials. When hot asphalt and sulfur are mixed, some of the sulfur, about 20 percent by weight of the asphalt, will dissolve in the asphalt. The remainder of the sulfur forms a dispersion of sulfur in asphalt. Both the dissolved and the dispersed sulfur modify the properties of the asphalt. Some of the dissolved sulfur reacts chemically with the asphalt to form polysulfides, which make the asphalt softer and more ductile. (At higher 193 temperatures, above 160° Celsius, dehydrogenation occurs with the formation of hydrogen sulfide (H)$) and harder, more viscous asphalts. This type of reaction is undesirable, and is one of the reasons why temperature control is important in SA technology.) The dispersed sulfur is present as droplets, most of which are below 5 micrometers in size. These solidify as the paving material cools below the melting point of sulfur (120° Celsius), and the resulting solid sulfur phase imparts increased structural strength to the SA paving material. (2) Properties. Listed below are some of the improved properties of SA paving materials: (a) The strength of SA, as measured by the Marshall method, can be designed to be considerably higher than that of regular asphalt; (b) the increased strength obtainable with SA may permit the use of lower quality aggregates or a reduction in paving thickness; (c) SA increases the high temperature stiffness of paving materials, without a corresponding increase at low temperatures, thus softer asphalts can be used to minimize winter cracking, with less danger of deformation at summer temperatures; (d) SA has a lower viscosity than regular asphalt and can be mixed at lower temperatures, resulting in reduced energy consumption at the hot-mix plant; (e) SA improves resistance to water stripping (the breaking of the bond between asphalt and aggregate by a layer of water that forms on the surface of some types of aggregates), thus aggregates which would otherwise be unsuitable can be used, and the use of antistripping agents can be reduced or eliminated; (f) resistance to gasoline, diesel fuel and other solvents is improved; and (g) stress fatigue characteristics are improved. Not only are many of the properties of SA superior to other concrete binder mixes, but also some of these properties may be enhanced by combina- tions of SA with other materials. The combination of sulfur-asphalt and a nonwoven fabric results in a high performance product that has high tensile strength, is capable of withstanding considerable deformation without break- ing, and remains waterproof even when placed on sharp aggregate. The lower viscosity of SA improves the impregnation of the fabric and the ductility of SA improves the fabric's low temperature performance. On solidification, the finely dispersed sulfur particles impart additional strength to the impregnated fabric. (3) Placement. The SA hot-mix is handled like regular asphalt hot- mix paving material. Equipment and technology for transporting, placing, and e 194 compacting the SA material is identical to that used for regular asphalt hot-mix. c. Sulfur Concrete. During the past 5 years, interest in sulfur con- crete (SC) has grown rapidly. Research and development on SC is currently being carried out by at least 50 companies and agencies, some of which are now actively marketing SC products and materials. Sulfur concretes are basically simple materials, made by mixing sulfur plus certain additives with heated mineral aggregates. On cooling, SC sets to give a high-strength material with superb corrosion resistance. Early attempts to make and use SC date back more than 100 years. However, current SC technology is a product of the 1960's and 1970's following the discovery and development of suitable additives or "plasticizers" for the sulfur which impart durability to SC. A considerable number of compounds have been screened as additives. Currently, the most popular ones are dicyclo- pentadiene (DCPD), dipentene (DP), certain proprietary polymeric unsaturated hydrocarbons, and combinations of these materials. Much of the current research work is concentrated on finding additives or combinations of additives which will further improve the durability and performance of SC. Sulfur concretes can be designed to have compressive and tensile strengths twice or more those of comparable Portland cement concretes (PCC), and full strength is reached in hours rather than weeks. Sulfur concretes are extremely corrosion resistant to many industrial chemicals, including most acids and salts. Sulfur concrete is highly resistant to saltwater, and marine applications may be attractive. (1) Additives. While satisfactory SC had been obtained by the addition of 5 percent DCPD as a modifier to the sulfur, recent U.S. Bureau of Mines work indicates that a superior product can be obtained by the use of mixed modifiers. These consist of a mixture of DCPD fractions from DCPD manufacture containing three, four, or more units of cyclopentadiene or methylcyclopentadiene per molecule. Several companies market materials of this type. The relative amounts of DCPD and oligomer used in the modifier will vary to some extent with the type of aggregate, but a mixture of 65 percent DCPD and 35 percent oligomer is about optimum in most cases. Five percent by weight of this mixed modifier is added with stirring to the molten sulfur at 130 Celsius, and allowed to react with it for several hours. To ensure complete reaction of the sulfur with the modifier, the U.S. Bureau of Mines allows the mixture to react for 24 hours, but there are indications that this time can be shortened considerably. The use of mixed modifier rather than straight DCPD results in improved durability and corrosion resistance. It is also easier to prepare the modified sulfur using the mixed modifier. The reaction of DCPD with sulfur is exothermic, and care must be exercized when adding straight DCPD to molten sulfur to prevent overheating. With mixed modifiers, the reaction is easier to control. (2) Aggregates. A metallurgist at the U.S. Bureau of Mines (W.C. McBee, Boulder City Laboratory, personal communication, 1981) stressed that each aggregate system must be analyzed and evaluated as to its suitability for SC. Generally, limestone aggregates tend to give SC higher strength 195 and freeze-thaw resistance, whereas quartz aggregates give higher corrosion resistance. The salts in chloride and sulfate-containing aggregates have no effect on bonding, but some aggregates are unacceptable for SC because they react chemically with the binder. Aggregates containing swelling clays are also undesirable. (3) Mix Proportions. Design is normally for maximum compressive strength, and based on the VMA (voids in mineral aggregate) procedure. Optimum strength generally coincides with maximum workability and minimum voids level. Coarse and fine aggregates blended to give about 25 percent VMA were found to be optimal. In the finished SC, 4 to 5 percent voids remained. These voids are not interconnected, and moisture absorption by SC is very low, 0.05 percent or less, whereas PCC often absorbs 3 percent or more. This is an important factor in the resistance of SC to corrosion. Aggregate grading according to ASTM specification is unsatisfactory for SC. From 6 to 10 percent of fine (200 mesh) material should be included to provide good workability. To prevent dusting, the fine material can be mixed with the modified sulfur before it is added to the heated aggregate in the mixer. (4) Properties and Uses. The quick curing characteristics of SC make the material attractive in many situations. Eighty percent or more of final strength is reached within a few hours of pouring, compared to several weeks for PCC. Moreover, SC will cure equally well under freezing conditions, which are highly detrimental to PCC curing. SC can tolerate chloride and sulphate-containing aggregates found in desert areas, because the bonding properties of sulfur are not affected by salts. The good heat insulation characteristics of sulfur and the elimination of water in the manufacturing process are two additional advantages of SC in desert areas (The Sulphur Institute, 1979). (a) Fire Effects. The inherent flammability and low melting point of sulfur impose some limitations of SC use. Flammability can be controlled to some extent by the use of additives, and it is fortunate that the DCPD types of additives used to improve the durability of SC also impart a degree of fire resistance. Sulfur concretes are in any case considerably less of a fire hazard than wood. Because of the low thermal conductivity, heat penetration is slow, and SC can survive short exposures to fire without serious damage. Sulfur concretes do not support combustion, and flame spread is essentially zero. (b) Structural Use Limitations. The low melting point of sulfur limits the use of SC in applications where loss of structural strength in event of a fire could be catastrophic. Thus, SC for load- bearing structures will probably not be used in high-rise apartment buildings. However, the properties of SC appear to make it fully acceptable for single-story dwellings, as well as for utility buildings and a wide range of prefabricated structures. These materials are well suited to specific uses in the coastal zone environment, and when used in a restricted manner may resist coastal environments for many years. 196 6. Environmental Considerations. a. Corrosive and Pollutant Attacks on Exposed Surfaces. (1) Bituminous Asphalt. Bituminous asphalt is stable in the presence of nearly all chemically-laden substances; however, because asphalt is refined from petroleum-based products, exposure to petroleum solvents will cause deterioration and disintegration of asphalt. It is normally unaffected by usual concentrations (less than 1 normal) of acids, salts and other waste materials. (2) Preplaced Aggregate Concrete. Preplaced aggregate concrete, like Portland cement concrete, is rarely attacked by solid, dry chemicals. Corrosive chemicals must be in some minimum concentration and usually are sulfates or acids. Also organic acids such as acetic, formic, and lactic can be quite destructive to preplaced aggregate concrete. (3) Portland Cement Grout. This grout is attacked by the same chemicals as Portland cement concrete; however, if the grout is not of equal density as concrete then the chemical attack may be more aggressive. (4) Soil Cement. Soil cement in its normal use is not attacked by most chemicals except for natural occurring sulfates such as sodium, potas- sium, and calciun. (5) Sulfur Cement and Grout. Sulfur cement and grout are not generally affected by pollutants in the coastal or marine environment and they can tolerate chloride and sulfate-containing aggregates. They are highly resistant to the corrosive effects of saltwater (The Sulphur Institute, 1979). b. Sunlight Exposure Effects. (1) Bituminous Concrete. Bituminous concrete weathers only at the surface when exposed to sunlight and air. The weathering results in the very slow evaporation of solvents near the exposed surface, but because of the impermeability of asphalt the solvent loss is very slow. (2) Preplaced Aggregate Concrete. This concrete is not affected by sunlight when properly protected from evaporation of mixing water during the curing period. (3) Portland Cement Grout. This grout is not affected by sunlight. (4) Soil Cement. Soil cement is not affected by sunlight. (5) Sulfur Cement Concrete and Grout. Sulfur cement concrete and grout does not appear to be affected by sunlight; however, being a relatively recent material development, experience is limited. c. Water Penetration Effects. (1) Bituminous Concrete. This concrete is highly resistant to water penetration because of the impermeability of asphalt. Formulations 197 can be used in porous structures; however, the asphalt does not deteriorate in the presence of water unless accompanied by petroleum solvents. (2) Preplaced Aggregate Concrete. This concrete is not normally penetrated by water, but seawater with a high sulfate and chloride content may be moderately aggressive as on Portland cement concrete. (3) Portland Cement Grout. Portland cement grout will undergo the same environmental effect as preplaced aggregate concrete. (4) Soil Cement. Soil cement will not be affected by water penetra- tion. (5) Sulfur Cement Concrete and Grout. Sulfur cement concrete and grout will not be affected by water penetration. d. Wave and Current Effects. (1) Bituminous Concrete. Bituminous concrete is not affected by normal waves and currents unless they have sufficient force to carry sus- pended matter to cause severe abrasion. The abraded asphalt particles are a stable compound and sufficiently diluted as to not cause any measurable impact on the adjacent environment. (2) Preplaced Aggregate Concrete. Preplaced aggregate concrete exhibits no effects from waves and currents. (3) Portland Cement Grout. Portland cement grout also exhibits no effects from waves and currents. (4) Soil Cement. Soil cement should not be used in a wave and current environment as it is brittle and subject to damage by wave impact. (5) Sulfur Cement Concrete and Grout. Sulfur cement concrete and grout exhibits no direct effect due to waves and currents. Wear by abrasion and cavitation can result from severe wave action. e. Effect of Severe Temperature and Ice. (1) Bituminous Concrete. Bituminous concrete may be either a hot- mix or cold-mix design. When mixing temperature should be only sufficient to ensure dry aggregate but in no case should it exceed 163 Celsius (325 Fahrenheit). Exposure to higher temperatures will cause solvents to dissi- pate resulting in deterioration of the asphalt concrete. Ice does not affect bituminous concrete; however, severe cold temperature will cause the concrete to become brittle. (2) Preplaced Aggregate Cement. Preplaced aggregate cement is generally not affected by severe temperatures. Air-entraining admixtures will further improve resistance to freezing and thawing as in Portland cement concrete. (3) Portland Cement Grout. Portland cement grout is also highly resistant to the effects of severe temperatures. Like preplaced aggregate 198 cement, its resistance can be further enhanced with addition of air entrain- ing admixtures. (4) Soil Cement. Soil cement is seldom exposed to severe tempera- tures and ice as these conditions require an increase in cement content resulting in a substantial increase in cost and may eliminate the considera- tion of soil cement as a construction element in this environment. For severe exposures it is important to note that an excess of cement is not harmful but that a deficiency of cement will result in inferior soil-cement resulting in cracking and spalling. (5) Sulfur Cement Concrete and Grout. Sulfur cement concrete and grout because of the low melting temperature of sulfur (130° Celsius) will deteriorate at elevated temperatures. Low temperatures have little effect on this material. f. Marine Organisms. (1) Bituminous Concrete. Bituminous concrete is subject to deterioration from crustaceous organisms as it is comparatively soft as a coastal environment construction material. When used as a binder with other materials such as large stone, this type of deterioration has little effect on the structure. (2) Preplaced Aggregate Concrete. Preplaced aggregate concrete is not affected by marine organisms. (3) Portland Cement Grout. Portland cement grout is not affected by marine organisms if properly mixed and placed. (4) Soil Cement. Soil cement is not usually exposed to an environ- ment containing marine organisms. When it is, many organisms will become attached to the rough surface of an exposed soil cement surface and cause spalling. Boring animals can penetrate the surface but apparently do not find it a desirable environment; therefore it is not a common condition. (5) Sulfur Cement Concrete and Grout. Sulfur cement concrete and grout has not shown any deterioration from marine organisms; however, due to the limited experience with this material, long-range performance experience is not available. g. Periodic Wetting and Drying. (1) Bituminous Concrete. Bituminous concrete surfaces may tend to develop fine cracks or alligator patterns on exposed surfaces when subjected to alternated wetting and drying. Such cracks seldom develop any signficant depth in asphalt concrete and are not serious in coastal struc- EUGeS)- (2) Preplaced Aggregate Concrete. Preplaced aggregate concrete is subject only to the same action as Portland cement concrete, i.e., the formation on the surface of 'D cracks" usually in random patterns. These are normally restricted to the surface and do not contribute to serious deterioration. 199 (3) Portland Cement Grout. Portland cement grout will react similarly to preplaced concrete. (4) Soil Cement. Soil cement may be exposed to alternate cycles of wetting and drying; however, because of the nature of this material it tends to harden until all the cement content is fully hydrated. Sufficient experience is not available to predict the long-term effects; however, because of the hardened condition improved resistance to wetting and drying is a reasonable expectation. (5) Sulfur Cement Concrete and Grout. Sulfur cement concrete and grout is unaffected by periodic wetting and drying. h. Wind Erosion. None of the five materials discussed in this section are subject to change or deterioration by wind. Strong winds may pick up sand particles that may cause some etching of their exposed surface over extended periods of time. i. Effects of Burrowing Animals. (1) Bituminous Concrete. Bituminous concrete, being a petroleum- base product, is an inhibitor to animals. It contains no food value and therefore is unaffected by animals. (2) Preplaced Aggregate Concrete and Portland Cement Grout. Preplaced aggregate concrete and Portland cement grout (as in Portland cement concrete) are very hard materials and not disturbed by burrowing animals. (3) Soil Cement. Soil cement used primarily to stabilize soil, is not as hard a material as Portland cement concrete. It can be attacked by burrowing animals but because of the shape and mass of these structural elements (foundations), usually any damage is minor and insignificant. (4) Sulfur Cement Concrete and Grout. Sulfur cement concrete and grout is also hard and resistant to activities of burrowing animals. The sulfur content is also a deterrent. j. Effects of Flora. There are no reports of flora growth having any effect on any of the five materials discussed in this section. Ike RaLTe@e (1) Bituminous Concrete. Bituminous concrete, because of its petroleum-base content, is subject to serious damage by fire. However, because the asphalt binder in this concrete contains very little solvent, it does not normally sustain burning itself. (2) Preplaced Aggregate Concrete and Portland Cement Grout. Preplaced aggregate concrete and Portland cement grout are resistant to fire and extreme high temperatures. (3) Soil Cement. Soil cement is fire resistant. 200 (4) Sulfur Cement Concrete and Grout. The inherent flammability see’. 3 and the low melting point of sulfur (130° Celsius) results in the loss of structural strength, causing the immediate deterioration of a structure. 1. Abrasion. (1) Bituminous Concrete. Bituminous concrete has a substantial resistance to wearing away by rubbing and friction. Not being as hard a material as Portland cement concrete or steel, it is not highly resistant to severe impact by large particles; however, it has a high degree of resistance to normal sand or wind abrasion. Precise limits for abrasion resistance are not possible to determine and it is usually best to rely on an analysis of specific environmental conditions to evaluate the physical properties of the designed bituminous concrete to be used. (2) Preplaced Aggregate Concrete and Portland Cement Grout. Pre- placed aggregate concrete and Portland cement grout are subject to abrading or etching by wind or waterborne particles; however, the slow rate of the abrasion process in the coastal zone is usually unnoticeable. Abrasion of structures above the water surface may result in some minor dusting problem. (3) Soil Cement. Soil cement when used as an integral part of a foundation, is not subject to abrasion. When used as a surface stabilizer it will wear quite readily, if subjected to surface traffic, and result in increased dusting. (4) Sulfur Cement Concrete and Grout. Sulfur cement concrete and grout have a relatively high resistance to abrasion. It is believed that admixtures can enhance these properties. Because of the short field exper- ience of this relatively new material, research and testing is still under- way to develop admixtures that can improve abrasion resistance properties of this material. m. Seismic Effect. (1) Bituminous Concrete. Bituminous concrete, not being a struc- turally rigid material, does not resist seismic forces or movement of the earth. Instead, its properties of plasticity and the ability of asphalt to flex allow it to move with a seismic event and thus reduce the possible damage to structures. (2) Preplaced Aggregate Concrete and Portland Cement Grout. Pre- placed aggregate concrete and Portland cement grout resistance to seismic effects is primarily a design problem. Severe seismic forces can cause structural failure by direct structural damage or by altering the foundation condition, resulting in structure settlement and failure or deterioration. (3) Soil Cement. Soil cement in its use in coastal structures is usually unaffected structurally by seismic activity, but it may shift with earth movement resulting from seismic-induced stress. (4) Sulfur Cement Concrete and Grout. Sulfur cement concrete and grout resistance to seismic effects is similar to that of Portland cement 201 concrete. Seismic forces can cause structure failure hy producing excessive stress in the material, resulting in structural deterioration. n. Human Activity. Human activity has very little impact on structures of these materials except where visual impact may be noticeable resulting from graffiti or other defacing action. 7. Uses In Coastal Structures. a. General. (1) Bituminous Concrete. Bituminous concrete is used to perform three basic functions in coastal construction. [It is used as a binder or filler to stabilize quarrystone work or soils, as a sealant to prevent the migration or flow of liquids, and, in its asphaltic cement form, as a wearing surface that can be easily repaired or replaced as it is eroded. Bituminous materials are also used in the preservative treatment of wood as discussed in Section VIII, Wood. (2) Preplaced Concrete. Preplaced concrete is usually used in large dimension mass concrete structures when aggregate larger than can be conveniently handled by ordinary mixing methods is desired. (3) Portland Cement Grout. Portland cement grout is used generally as a filler and binder for quarrystone work and as a stabilizer for soils. (4) Soil Cement. Soil cement is used to strengthen foundation soils and to resist erosion of selected layers of soil. (5) Sulfur Cement and Grout. Sulfur cement and grout are resistant to many environmental attacks in the coastal zone and may become economical to use due to an increasing abundance. Because of limited general use and history, sulfur cement and sulfur asphalt must be considered unproven materials. However, the property of reaching full strength on cooling could be especially useful in making repairs to structures and embankments where the cost of delay is high. In busy cargo terminals, on heavily used roads or in coastal structures subject to imminent assault by storms, quick repairs to structures not immersed in water could be made. No practical techniques for placing sulfur concrete under water have been developed to date. (Fast cooling is the problem.) b. Offshore Structures. (1) Bituminous Concrete. Bituminous concrete is used for reinforce- ment or grout to fill and plug the yoids in stone or rubble-mound breakwaters. The binding action of the mastic tends to produce a large firm mass while being flexible enough to conform to some differential settlement of the structure (Fig. 44.) (2) Preplaced Concrete. An impermeable breakwater could be made by placing uniformly graded stones in layers along the contours of a rubble- mound breakwater. Each layer would be bound together with tremie-placed Portland cement concrete grout. The resulting mass concrete structure would be accomplished by the preplaced concrete method except that no forms would be used. 202 c. Shore-Connected Structures. (1) Breakwaters, Jetties and Groins. Breakwaters, jetties and goins could be made in the same manner as offshore structures using bitumi- nous concrete or preplaced aggregate methods. (2) Seawalls. (a) Bituminous Concrete. In addition to the types of uses described for offshore structures, bituminous concrete products and sealers may be required to make impermeable membranes, where required. (b) Preplaced Concrete. Preplaced concrete techniques can be used for mass concrete seawalls. Forms for the vertical or specially contoured faces would be required. Otherwise, the placement methods would be as described for offshore structures except that a tremie may not be necessary for layers placed above the waterline. For good void filling, a vibrator would be used to ensure that the concrete grout flows into all the voids and fills the form. (c) Portland Cement Grout. Portland cement grout would be used to fill synthetic mesh bags and tubes used to form seawall units. (3) Revetments. (a) Bituminous Concrete. Bituminous concrete is used to bind stone blankets together to form a stable mass or can be used by itself as slope protection, as shown in Figure 43. (b) Portland Cement Grout. Portland cement grout may be used to bind stones in a blanket together to form a stable but brittle mass. It can also be pumped into weak soils to firm them for foundations or can be used to fill voids in earth layers to obtain foundation continuity. (c) Soil Cement. Soil cement techniques may be used where the slope is composed of the right type of soil and the exposure is not subject to severe wave action. It has the advantage of not requiring aggregate materials to be hauled to the site. (4) Piers and Wharves. (a) Bituminous Concrete. Bituminous concrete wearing surfaces are sometimes used to provide an economical surface to be sacrificed to the wear of ordinary use. Replacement or refurbishment is easily and cheaply done and the underlying structure remains undisturbed. (b) Preplaced Aggregate Concrete. Preplaced aggregate con- crete has been used along the perimeter of landfills to act as a combination seawall, retaining wall, and wharf structure. Such structures are usually topped with a large reinforced concrete wall that supports the fender system and forms the "face of wharf." 203 VIT. STRUCTURAL AND SHEET METALS 1. Types and Characteristics of Metals and Alloys. a. Steel. Steel has been an important construction material for marine service since the late 1800's. Steel obtained this dominance at the expense of wood and iron because of greater strength and availability. Although other materials may have advantages, such as corrosion resistance, steel is relatively inexpensive, strong, and available in various shapes and sizes for marine application. To ensure the quality of the material used in construction, materials are purchased to specifications. ASTM standard specifications define the requirements to be satisfied by the particular material and indicate the procedure by which it may be determined that these requirements are met. ASTM Standard A6, "Standard Specification for General Requirements for Rolled Steel Plates, Shapes, Sheet Piling, and Bars for Structural Use," lists a number of specifications for materials that are Suitable for marine application. Other ASTM specifications cover pipe, mechanical tubing, fittings, forgings, and other materials. ASTM specifica- tions both from ASTM Standard A6 and other appropriate ASTM specifications for steel materials, suitable for marine application, are included in Appendix A. (1) Metallurgy. (a) Carbon Steel. Metallurgists define carbon steel as an alloy of iron and carbon with the carbon content under 2 percent. Structural steel specifications limit carbon to 0.35 percent or less for weldability considerations. Manganese is added to improve strength and toughness, but mostly to aid in the deoxidation of steel during refining and modify the detrimental effects of sulfur. Sulfur causes steel to be "hot short," i.e., to be brittle at high temperatures, which can lead to cracking during hot rolling and forging. Manganese combines with sulfur in the molten steel to form insoluable manganese sulfide, some of which is removed as slag, and the remainder as well distributed inclusions throughout the steel. The shape of these sulfide inclusions can be controlled by special processing during the steelmaking process. Phosphorous is also present as an impurity. Most steel specifications require the phosphorous content to be less than 0.05 percent because larger percentages of phosphorous cause a decrease of ductility and toughness, rendering the steel to be "'cold short."' Silicon is often added as a deoxidizing agent during the melting and refining of steel. Copper may also be present up to 0.25 percent. (b) Carbon Steel Alloys. Depending on the alloy content, carbon steel can be classified as low, medium, or high alloy. Carbon steel contains only residual elements and elements, such as manganese and silicon, added during the melting and refining stage to obtain a workable product. Low alloy steel contains up to 1.5 percent of elements added to obtain increased strength or heat treatment capability. Medium alloy steel contains 1.5 to 11 percent added alloy elements. Above 11 percent alloy element content, the steel is classified as high alloy. The high allay steels include both the ferritic and austenitic stainless steels. 204 (2) Processing. (a) Deoxidation and Classification. Steels are classified on the basis of the amount of gases evolved during solidification. In the manufacture of steel from pig iron, excess carbon is removed by the exposure of the molten metal to oxygen or air until the desired carbon content is reached. Oxygen dissolves in the molten metal and reacts with carbon to form bubbles of carbon monoxide, which rise to the surface. Other sources of oxygen include that contained in materials added to the slag or molten metal and that present as a product of chemical reactions that occur during the steelmaking process. Because carbon and oxygen may continue to react during solidification, or the steel may have an unacceptably high oxygen content, deoxidation in the ladle of the molten steel may be required. The deoxidation practice, which may or may not be specified by the steel specifi- cation, is often an important consideration in choosing a steel for a particular application. Steels having decreasing degrees of gas evolution or deoxidation are termed "rimmed," "capped," "semikilled," and "killed." Figure 47 shows sketches of typical ingot cross sections corresponding to these degrees of deoxidation. KILLED SEMIKILLEO CAPPED RIMMED Figure 47. Typical ingot structures Rimmed steels do not receive any silicon or aluminum deoxidation before being poured into ingots. Carbon and oxygen dissolved in the molten steel continue to combine forming small bubbles which effervesce during solidifica- tion. Some effervescence is also due to the much lower solubility of oxygen in solid steel compared to that in molten steel. Chemical composition 205 varies widely throughout rimmed steel ingots. The area near the surface is much lower in carbon, sulfur and phosphorus than the remainder of the ingot. This low carbon skin persists to the finished mill product which contributes to the superior deep drawing properties of rimmed steel. Capped steel is similar to rimmed steel except that the effervescence of gas from the molten steel in the ingot mold is only allowed to occur for a minute or so before a cast-iron cap is placed on the mold. Capped steel has a thinner low carbon rim than rimmed steel but is of more uniform composi- tion. Capped steel is used for plate, strip, pipe, trim plates, wire, and bars. Semikilled steel is produced by additions of silicon and other deoxida- tion elements during the manufacture. These additions are carefully made in order to balance evolution of gases with solidification shrinkage. Semi- killed steel is used for structural shapes, plate, pipe, forging billet and bars. Killed steel is produced by the addition of excess deoxidizers over the amount required to fully remove all oxygen from the ladle. As the molten killed steel solidifies, a large shrinkage cavity forms, called the pipe, as shown in Figure 47. It is necessary to cut off the top of killed steel ingots at the bottom of the pipe to avoid producing a defect, known as a seam, in the rolled product. Killed steel is more uniform in both composi- tion and mechanical properties than semikilled steel. However, because of the low yield of product per ingot, killed steel is more costly than semi- killed steel. The choice of deoxidizer used is often dictated by the specification chosen by the user after considering the end use. If high temperature use is contemplated (for instance for use in a steam boiler) silicon coarse- grain killed steel will be specified because of its improved resistance to deformation at high temperatures. When improved resistance to brittle failure is desired, particularly for service at temperatures below 20 Celsius (68 Fahrenheit), a silicon-aluminum dioxidation practice will be specified so as to produce a steel having a fine-grain structure. Vacuum degassing is also used when premium quality is required. (b) Heat Treatment. Mechanical properties of steel can be altered by heat treatment. When steel is heated above a critical tempera- ture (the specific temperature depends on the composition), transformation of the microstructure into a single phase solid solution occurs. This solid solution is called austenite. The temperature at which transformation takes place is called the austenitizing temperature. Steel heated to the austen- itizing temperature and allowed to cool in the furnace to a temperature low enough for the steel to be handled is said to be annealed. Annealing is performed to reduce hardness, improve machinability, and facilitate cold working. Normalizing is the process of heating the steel above the austenitizing temperature, allowing sufficient time for transformation to occur, and then removing the steel from the furnace and cooling in air. Normalizing is performed to refine grain size and homogenize microstructure, improve machinability, and or provide the desired mechanical properties. Normalizing 206 is usually performed on steels requiring additional heat treatment for hardening, on hot formed pressure vessel heads, and when specified by the applicable material specification. Steels having sufficient carbon can be hardened by heating above the austenitizing temperature, holding at this temperature long enough for transformation to occur, removing the steel from the furnace, and immediately quenching it in water or oil. The resulting surface hardness depends on the carbon content, section size, and quenching medium. The depth of hardening depends also on alloy content and grain size. After quenching, steels are tempered by heating to a specified temperature (below the transformation temperature) and holding them at this temperature for a specified time, usually an hour per 2.54 centimeters of thickness. This process restores ductility. The particular tempering temperature used depends on the alloy content, mechanical strength requirements, and end use. Low carbon steels are often stress relieved by heating between 593° Celsius (1100 Fahrenheit) and the austenite transformation temperature to remove resudial stresses resulting from prior forming or welding operations. Stress relieving restores ductility and toughness. It may also improve fatigue life. Welds areas are often postweld heat treated locally, i.e., stress relieved, using proprietary portable heating equipment. (c) Alloy Additions. Alloying elements are added during the steelmaking process to improve mechanical properties or to improve corrosion resistance. Small additions, singly, of copper, nickel, chromium, silicon, and phosphorus have been shown to be effective in improving the corrosion resistance of steel. The greatest improvements in corrosion resistance are obtained by the addition of specific combinations of these alloying elements, such as specified by ASTM Standard A690 for H-piles and sheet piles intended for service in the splash zone. Other steels suitable for marine applications and having improved atmospheric corrosion resistance are ASTM Standards A242, A441, and A588. Additions of chromium and molybdenum improve the high temperature oxida- tion resistance as well as improve the high temperature strength of steel. High-pressure steam tubes and piping are often 1.25 percent chromium alloy steel. Stainless steels meeting ASTM 400 series specifications include type 410, with 12 percent chromium, and type 430 with 18 percent chromium. However, because of a tendency to pit, the 400 series stainless steels are not recommended for marine service. b. Aluminum. (1) Alloy Strengthening. Aluminum, in high purity form, is soft and ductile but does not possess enough strength for most commercial applica- tions. The addition of alloying elements, either singly or in combination, impart strength to the metal. Aluminum alloys can be classified into two catagories: nonheat-treatable and heat-treatable. The nonheat-treatable wrought alloys can be strengthened by cold working only and are usually, designated in the 1000, 3000, 4000, or 5000 series. The degree of cold working is termed the aluminum strain hardening or temper, denoted by an "H" followed by a number. 207 Certain alloying elements, such as copper, magnesium, zinc, and silicon, show increasing solid solubility in aluminum with increasing temperatures. Many aluminum alloys containing these elements can be heat treated to enhance the initial strength. These alloys are heat treated by first raising the alloy to an elevated temperature below the melting point, called the solu- tioning temperature, which puts the soluble element or elements into solid solution. This is followed by quickly cooling the material, usually by quenching in water, to retain the elements in solid solution at room tempera- ture. At this stage the freshly quenched alloy structure is very workable. By storing such material at below-freezing temperatures, this workable alloy structure can be retained until the fabrication is ready to form the alloy into the desired final shape. Such alloys after quenching are not stable at room or elevated temperatures because precipitation of the constituents from the supersaturated solution takes place. After a period of several days at room temperature or hours at an elevated temperature, the alloy is consider- ably stronger. This process is called age hardening or precipitation harden- ing. The degree of hardening or temper produced by heat treatment is denoted by a "'T" followed by a number. (2) Identification of Aluminum Alloys. Aluminum alloys are identi- fied by specific numbers. Alloys belong to certain series depending on the particular alloying elements. The 1000 series consists of the high purity aluminums containing at least 99 percent aluminum. These alloys are char- acterized by having high thermal and electrical conductivity, excellent corrosion resistance, excellent workability, but low strength. These alloys can only be hardened by cold working. Major impurities are iron and silicon. Copper is the major alloying element of the 2000 series. These alloys are solution heat treated to obtain optimum properties. Some alloys of this series are aged at slightly elevated temperatures, a process called artifi- cial aging, to obtain increased yield strength. The corrosion resistance of the alloys in the 2000 series is less than most of the other aluminum alloys. Sheet forms of these alloys are often clad with high purity alloy or a magnesium-silicon alloy of the 6000 series which provides galvanic protection to the core material and therefore increases resistance to corrosion. Manganese is the principal alloying element of the 3000 series alloys. Alloys of this group generally cannot be heat treated, but can be hardened by cold working. Silicon is the major alloying element of the 4000 series, which in sufficient quantities, lowers the melting point without producing brittle- ness. Aluminum-silicon alloys are used in welding and brazing wire where the lower melting point is beneficial in joining other aluminum alloys. Although most alloys of this group are nonheat-treatable, during welding of heat-treatable alloys, some elements from the parent material may be picked up by the weld metal providing joints that may be strengthened by heat treatment. The 5000 series of alloys contains magnesium. Although these alloys are nonheat-treatable, the addition of magnesium produces alloys having moderate to high strength, good welding characteristics, and good corrosion resistance to marine atmospheres. These alloys are subject to stress corrosion cracking if employed in the cold-worked condition in services where the temperature exceeds about 65 Celsius (150 Fahrenheit). 208 The 6000 series of aluminum alloys contains both silicon and magnesium in approximate equal proportions which combine during melting to form magnesium silicide. Alloys of this series are heat-treatable, and possess good formability and corrosion resistance with medium strength. One of the most versatile heat-treatable alloys is the major alloy of this series, 6061. Zinc is the major alloying element of the 7000 series, and when coupled with a smaller percentage of magnesium results in heat-treatable alloys of very high strength. Small amounts of other elements such as chromium and copper also may be added. Alloys in this series are used in air-frame structures and for high-stressed parts. Among the high strength aluminum alloys, 7075 can be heat treated to 565 megapascals (82 000 pounds per square inch) tensile strength, and 496 megapascals (72 000 pounds per square inch) yield strength. The complete designation of aluminum alloys includes the temper designa- tion, separated from the alloy designation by a hyphen, as for example 7061- T6. The basic temper designations are as follows: F as fabricated - no special control is exercised over thermal con- ditions or strain hardening. O annealed - heat treated to obtain lowest strength temper and improved ductility. H strain hardened (wrought products only). W solution heat treated (applies only to alloys hardenable by thermal heat treatment) - an unstable temper, describing the condition between solution treatment before aging. Subfreezing is sometimes used to preserve this temper against natural aging. T thermally treated to produce stable tempers other than F, O, or H. Numbers following the basic temper designations further describe the specific combination of operations affecting the temper and in turn the mechanical properties. Specifications, such as those of the American Society for Testing and Materials (ASTM), fully define the alloy composition, mechanical properties and other requirements for applicable aluminum mate- rials. Alloys 5083, 5086, 5052, and 6061 are the most popular aluminum alloys for applications exposed to marine atmospheres. The 5000 series of alloys are the most corrosion resistant, but the 1000, 3000, and 6000 alloys have been used in marine atmospheres. These aluminums may be also employed in the splash zone, but are not recommended for continuous immersion in seawater. c. Copper and Copper Alloys. Copper has several unique properties. Properties such as high thermal and electrical conductivity, excellent corro- sion resistance in normal atmospheric conditions, good workability, and availability at reasonable cost make copper a first choice for conductors in electrical equipment. Copper can be alloyed to produce alloys having improved strength, corrosion resistance, creep resistance, and machinability. 209 The U.S. copper industry through the Copper Development Association used to designate alloys by a three-digit identification system. This recently has been expanded to five digits, following a prefix letter C, and made part of the Unified Numbering System for Metals and Alloys (UNS) developed and managed jointly by ASTM and the Society of Automotive Engineers (SAE). In the UNS system, numbers C10000 through C79999 denote wrought alloys. Cast alloys are numbered from C80000 through C99990. Within these two catagories, the alloy compositions are grouped into families of coppers and copper alloys as presented in Table 27. Copper like other metals that have a recrystallization temperature, or softening temperature, above room temperature can be hardened by cold working. If the cold-worked metal is exposed to temperatures above a certain critical temperature determined by the amount of cold work received and the composition of the metal or alloy, the microstructure changes from marked distortion to a recrystallized structure. Yield strength, tensile strength, and hardness are reduced to the same as the alloy had before cold working. The recrystalliza- tion temperature or softening temperature of copper can be raised by adding sufficient quantities of silver, phosphorous, cadmium, tin, arsenic, or antimony. Such coppers are often alloyed to raise the softening temperature to above that at which soldering is to be performed so that the benefits of increased strength due to cold working can be retained in the final product. Copper alloys that are precipitation hardenable contain berylliun, chromium, zirconium, or nickel in combination with silicon or phosphorus. Alpha aluminum bronze containing cobalt or nickel is also precipitation hardenable. During hardening, these alloys are heated to an elevated temperature, held a sufficient time for solid solutioning to occur, then rapidly cooled to room temperature, followed by aging at an intermediate temperature. Beryllium copper (C17200) in the solution annealed and aged condition has a usual tensile strength of 1 210 megapascals (175 000 pounds per square inch). Copper and copper alloys have useful corrosion resistance for marine application. Most corrosion resistant to seawater are aluminum brass, classified as a miscellaneous copper-zinc alloy; inhibited admiralty, a tin brass containing elements which inhibit the loss of zinc; and the copper- nickel alloys. These alloys form films of corrosion products that provide protection even in flowing seawater. The limiting velocity where these films are lost depends on the alloy. Copper and copper alloys are attacked by ammonium hydroxide due to the formation of a soluable component. Copper alloys containing more than 15 percent zinc are susceptible to stress corrosion cracking due to ammonium ion, and also dezincification, i.e., the loss of zinc due to selective corrosion. Stress corrosion cracking occurs at areas of high stress that can become more anodic than the surrounding metal. Corrosion occurs at the interfaces of the metal crystals that are perpendicular to the stress, weakening the bonding between crystals until cracking occurs. Dezincification occurs in waters having a high oxygen and carbon dioxide content. d. Other Alloys. Nickel aluminum bronzes and-two phase aluminum bronzes are transformation hardenable. These alloys are heat treated by heating to an elevated temperature to form a single phase solid solution, 210 Table 27. Classification of Cappers and Copper Alloys C10000 through C15999 Coppers (Cu2 99.3 pct) C16000 through C19999 High copper alloys (96 pct < Cu < 99.3 pct) C20000 through C29999 Copper-zinc-alloys (brasses) C30000 through C39999 Copper-zinc-lead alloys (leaded brasses) C40000 through C49999 Copper-zinc-tin-alloys (tin brasses) C50000 through C52999 Copper-tin alloys (phosphor bronzes) C53000 through C59999 Copper-tin-lead alloys (leaded phosphor bronzes) C60000 through C64699 Copper-aluminum alloys (aluminum bronzes) C64700 through C66399 Copper-silicon alloys (Silicon bronzes) C66400 through C69999 Miscellaneous copper-zinc alloys C70000 through C72999 Copper-nickel alloys C73000 through C79999 Copper-nickel-zine alloys (nickel-silver) C80000 through C81199 Coppers” (Cu"2"99"3 pct); cast C81200 through C82999 High copper alloys (96 pct < Cu < 99.3 pct), cast C83000 through C83999 Copper-tin-zinc and copper- tin-zinc-lead alloys (red brasses and leaded red brasses), cast C84000 through C84999 Semired brasses and leaded semired brasses, cast C85000 through C85999 Yellow brasses and leaded yellow brasses, cast C86000 through C86999 Manganese and leaded manganese bronze alloys, cast C87000 through C87999 Copper-zinc-silicon alloys (silicon bronzes and silicon brasses), cast C90000 through C91999 Copper-tin alloys (tin bronzes), cast C92000 through C94699 Copper-tin-lead alloys (leaded tin bronzes and high-leaded tin bronzes), cast C94700 through C94999 Copper-tin-nickel alloys (nickel-tin bronzes) C95000 through C95999 Copper-aluminum-iron and copper-aluminumn- iron-nickel alloys (aluminum bronzes), cast C96000 through C96999 Copper-nickel-iron alloys (copper-nickel), cast C97000 through C97999 Copper-nickel-zinc alloys (nickel-silver), cast C98000 through C98999 Copper-lead alloys (leaded copper), cast C99000 through C99990 Special alloys, cast 2il held a sufficient time for solutioning to occur, then cooled rapidly to produce a metastable, ordered, close-packed-hexagonal beta phase structure, much like the transformation structure that is formed during the quenching of high carbon steel from a temperature above the austenitizing temperature. This structure is very hard but too brittle for most engineering purposes and must be tempered by heating to an intermediate temperature, typically 595° to 650° Celsius, and holding for a sufficient time to reprecipitate fine acicular alpha phase particles in the tempered beta phase structure. Tempering stabilizes the structure and restores ductility and toughness. e. Galvanic Coupling. When two dissimilar metals are in electrical contact with each other and immersed in an electrolyte, a potential is established and electrical current may flow. This potential is related to the relative tendency of each of the metals to go into solution. The more active metal acts as the anode and corrodes at a faster rate than it would by itself. The more noble (stable) metal acts as the cathode and is pro- tected. This phenomenon is known as galvanic corrosion. The two dissimilar metals electrically connected are called a galvanic couple. Table 28 presents a galvanic series for flowing seawater at ambient temperature for several metals and alloys. This galvanic series is based on practical measurements of corrosion potentials at equilibrium in seawater. Galvanic corrosion is most likely to occur if the two metals are widely separated in the series. The rate of corrosion is dependent on current density. Table 28. Galvanic series in flowing seawater (2.4 to 4.0 m/s) at ambient temperature. Magnesium Zinc Aluminum alloys Calcium Carbon steel Cast iron Austenitic nickel cast iron Copper - nickel alloys Ferritic and mortensitic stainless steel (passive) Nickel copper alloys, 400, K-500 Austenitic stainless steels (Passive) Alloy 20 Ni - Cr - Mo alloy C Titanium Graphite Platinum If two dissimilar metals must be joined, several steps may be taken to minimize galvanic corrosion: (1) Choose metals close together in the galvanic series to reduce the potential; (2) avoid unfavorable area effects by keeping the cathodic area small in relation to the anode, thereby reducing current density; 2l2 (3) insulate the two metals from each other, making sure contact is not restored in service by grounding or corrosion products bridging the insulator; (4) use coatings: the anodic material must be completely covered to prevent rapid attack at holidays in the coating; sometimes it is also beneficial to coat the cathodic material to reduce current density; and (5) place a more anodic third metal in contact with the other two so that this third metal provides sacrificial protection. 2. Joining, Cutting and Repairing Metals. a. Rivets and Bolts. Riveting, at one time, was the primary means of joining metals together. Today the importance of riveting in construction has lessened because of the developments of welding and high strength bolting. The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code no longer lists riveting as an acceptable method for pressure vessel fabrication, although repairs can be made to riveted vessels in accordance with the code requirements that were used for the vessel con- struction. Riveted joints have one important advantage over bolted joints. Properly set, rivets do not loosen. In spite of its lack of favor in con- struction, riveting is an important joining method in manufacturing. Rivets are made from bar stock by hot or cold forming the head. Round button heads are most common but flattened and countersunk types are also produced. For structural steel fabrication, steel rivets should be specified to ASTM Standard Standard A502, Steel Structural Rivets. This standard lists three grades, all of which are intended to be hot driven. Grade 1 is a carbon steel rivet for general purpose, usually used for joining steel conforming to ASTM Standard A36. Grade 2 is a carbon-maganese steel rivet used for joining high strength carbon and high strength low alloy structural steels. Grade 3 is about the same strength as grade 2 rivet steel, but because copper and chromium are required in the steel composition, grade 3 rivets have enhanced atmospheric corrosion resistance approximately four times that of carbon steel without copper. Grade 3 rivets correspond to steels conforming to ASTM Standard 588, High Strength Low-alloy Structural Steel with 340 megapascals (50 000 pounds per square inch) Minimum Yield Point to 10.2 centimeters (4 inches) Thick. Steel rivets are also listed in ASTM Standard A31, Boiler Rivet Steel and Rivets, for repair of riveted boilers and pressure vessels, and in ASTM A131, Structural Steel for Ships. Rivets meeting the requirements of ASTM A31 or ASTM A131 are not suitable for structural construction unless these rivets have also met requirements of ASTM A502. One important difference in the requirements between these standards is that ASTM A502 requires hardness tests, whereas the other standards specify tensile tests on the rivet steel. Holes for rivets may be punched or drilled. If punched, it is recom- mended that the holes also be reamed to remove distorted metal, particularly if the structure may be suhjected to vibration. For steel construction, the holes are usually 1.6 millimeters (1/16 inch) in diameter larger than the nominal diameter of the undriven rivet. Flame cutting of holes is not recommended because of the microstructural changes that occur in steel. 213 Temporary bolts are often inserted in a few holes as an alinement aid and to help draw the structural steel memhers together. Steel rivets are usually driven hot by heating to 982° Celsius (1 sao? Fahrenheit). During driving a second head is formed and the riyet shank may be expanded to fill the hole. As the rivet cools, it shrinks and squeezes the connected pieces together. The magnitude of this clamping force depends on the driving and finishing temperature of the riveting operation, the overall grip length, and the driving pressure. Because these are variables that are difficult to control, no credit may be claimed for clamping force in design calculations. Riveting is used ta advantage in joining aluminum structural alloys that have been heat treated for greater strength. The high heat encountered in welding reduces the strength of heat-treated aluminum. Less skill is re- quired for riveting than for welding. The specification covering wire and rod to be used in aluminum rivet manufacture is ASTM Standard B316-75, Aluminum-alloy Rivet and Cold-Heating Wire and Rods. Of the listed alloys, alloys 1100, 3003, 5005, 5052, 5056, and 6061 are most suitable for joining aluminum alloys in coated structures. The 6061 alloy is the only alloy that can be heat treated to obtain higher strength levels. Bolts are made from bar stock. High strength steel bolts are made by open-hearth, basic oxygen, or electric furnace process. They are fine- grained and must meet ASTM Standard A588-75. The atmospheric corrosion resistance of this steel is approximately two times that of carbon structural steel with copper. High strength bolts are made using various types of quenching and tempering processes and are used in structural connections where high stress and corrosion resistance are required. Bolts are used to advantage in structural installation where welding is not practical and where working connections are necessary such as tongue and groove pile connections, bulkhead wales, and tiebacks. It is common practice to oversize bolt requirements in marine exposures as an allowance for exces- sive metal loss from corrosion. b. Welding. Welding processes most likely to be used during coastal structure construction include gas welding, arc welding, and thermite welding. Other processes, such as resistance welding, friction welding, and induction welding, are used during fabrication of mechanical and electrical equipment. Each welding process has areas of application where its use is the most economical for the desired level of quality. Gas welding is classified by the gases used; i.e., air-acetylene, oxy- acetylene, oxy-stabilized methylacetylene-propadine, and oxy-hydrogen. The, oxyacetylene flame has the highest temperature, about 3 371” Celsius (6 100 Fahrenheit), that can be obtained with commercially available gases. Because the temperature produced by the oxyacetylene flame is far above the melting point of most metals, rapid localized melting necessary for welding is produced. Oxyacetylene is suitable for welding carbon and alloy steel, cast iron, copper, nickel, aluminum and zinc. alloys. Lower melting temperature alloys, such as aluminum, magnesium, zinc, lead and some precious metals, can be gas welded using hydrogen, methane, or propane fuel gases. Gas welding is not 214 suitable for joining the refractioning metals such as columbium, tantaliun, molybdenum, and tungsten nor reactive metals such as titanium or zirconium. By varying the relative amounts of fuel gas to oxygen in the gases flowing to the tip of the welding torch, the characteristics of the flame can be altered. When fuel gas and oxygen are supplied in the stoichiometic ratio for complete combustion, a neutral flame is produced. As more oxygen is introduced, an oxidizing flame is produced. Slightly less oxygen than that required for a neutral flame results in a reducing flame. Still less oxygen results in a carhurizing or carbon impregnating flame. In any flame, the highest temperature is reached at the tip of the inner cone. In oxyacetylene welding, an oxidizing flame is never used to weld steel but is used sometimes to weld copper and copper base alloys. The copper oxide slag that forms on top of the_weld provides shielding from the weld puddle. Temperatures exceeding 315 Celsius (600 Fahrenheit) can be obtained in oxidizing oxyacetylene flames. The reducing flame is frequently used for welding with law alloy steel rods. Flame temperature at the tip of the inner cone is usually 2 930° to 3 040° Celsius (5 300 to 5 500° Fahren- heit). The carburizing flame has a tendency to soot the cold work but is useful where lower temperatures are required such as for silver brazing, soldering, and in the melting of lead. For most oxyacetylene welding, a neutral flame is used. When welding steel the outer envelope provides protection to the molten weld puddle, and no flux is required. Fluxes are required when oxyacetylene welding stainless steel, cast iron, and most nonferrous metals. There is no universal flux suitable for all metals. The function of the flux is to clean the metal surfaces to be joined and to provide protection ta the weld puddle by lowering the melting point of the metal oxides or dissolving these oxides so they rise to the top of the weld pool forming a protective slag covering. Fluxes are not required for welding lead, zinc, and some precious metals. c. Underwater Arc Welding. Although many experts consider underwater welding suitable only for emergency ship repairs of a semipermanent nature, satisfactory permanent welds can be accomplished using special. techniques. Sometimes underwater welding is the only practical method of making attach- ments or repairs on such underwater structures as drilling platforms or bulkheads. Three different techniques have been used for performing welding below the waterline. These are wet welding, dry welding, and welding using either a caisson open to the surface attached to the area to be welded, or a special habitat constructed around the area to be welded. Underwater wet arc welding requires the use of divers in full deep-diving suits. The helmets are fitted with supplementary hinged faceplates with appropriate welding glass. It is advisahle for the diver's head to be insulated from the helmet by wearing a cap, and by covering metal with insulating tape. Scuba diving is suitable only at shallow depths because it is required that the diver be in voice communication with tapside assistant. Topside welding assistants operate the power source at the command of the diver-welder. Electrodes for underwater welding must he waterproofed using proprietary products or coatings of cellulose acetate. Some brands of electrodes are also satisfactory without additional coatings. Because these coatings can be only considered as providing temporary protection, divers should carry only a few electrodes at a time. The Navy recommends 4.75-millimeter (3/16 inch) electrodes of 215 type E6013 for all positions except where the sectiagn size is tog thin for this size electrode. Qther electrodes, such as waterproofed iron powder electrodes, may he satisfactory. Qualification testing should be performed. Electrodes for underwater welding are designed for straight polarity, i.e., the electrode is negative. If reverse polarity is used underwater, the electrode holder is consumed due to electrolitic action. It is important that the electrode holder be insulated and be designed to permit easy changing of electrodes by the diver. Power sources for underwater arc welding should be capable of delivering at least 300 amperes of rectified or direct current. Because welding is usually done at considerable distances from the power source, the welding cables should be at least size 2/0. To facilitate maneuverability, the last 3 meters (10 feet) af cable at the electrode holder is usually size 1/0. A safety switch is installed in the circuit that is closed only while the welder is actually welding. For good electrical continuity, the ground cable must be securely attached to the work after first cleaning the contact area. Provided the pieces ta be welded fit together properly, 4.75-millimeter fillet welds can develop 44 kilonewtons (10 000 pounds) tensile strength per 25.4 millimeters (1 inch). Using 4.75-millimeter electrodes and the drag technique where the electrode is allowed to consume itself as it is pressed against the work, 4.75-millimeter fillet welds are produced in a single pass. Stringer bead technique should be used if additional weld reinforce- ment is required. Because visibility is poor under water, multipass welds are difficult to finish after the first bead is laid because the guiding groove is filled. Fillet welds can be made in the horizontal, vertical, and overhead positions. Bubbles generated during welding interfere with visibility. Welders minimize this problem by welding toward themselves when making horizontal welds and from the top down when making vertical welds. Underwater welds in mild steel plate develop 80 percent or more of the tensile strength, but only 50 percent of the ductility of similar welds made in air. This substantial decrease in ductility is explained by the hardening resulting from the drastic quenching of the surrounding water. Because it is not possible to preheat weld areas wet by water, to avoid cracking underwater welding should not be attempted on base materials having carbon contents above 0.25 percent or carbon equivalents (percent carbon plus 0.17 percent manganese) above 0.40 percent. The area to be welded must be free from marine growth, paint, mill scale, and rust to assure sound welds. Electric shock is a hazard that must be taken into account by equipment and safety procedures. Another hazard that could be overlooked is the possible explo- sion resulting from the accummulation of hydrogen and oxygen gas in closed or inadequately exposed compartments or spaces. Bubbles generated during arc welding are about 70 percent hydrogen and are produced by electrolysis of the water. Such accummulations of hydrogen can be ignited by spark or flame. Underwater work including welding has been accomplished dry in air using a caisson open to the surface. Such a structure must be strongly constructed to stand the pressure of the water, approximately 9.8 kilopascals per meter of depth (62.4 pounds per square foot per foot of depth), depending on salt content and temperature. A caisson has been used to repair a tear 13.7 216 meters (45 feet) helow the surface, in the stainless steel liner of a water- filled storage pool. Habitats haye been used to make underwater modifica- tions to a drilling platform in the Gulf of Mexico. Habitats can be con- structed to surround the areas to be welded and filled with air so that preheating of the weld areas is possible. Welds produced under these conditions will basically have the same strength and ductility as welds produced under the same condition topside. Habitats used in welding are usually open at the bottom. Because of buoyancy, the habitat must be securely attached and weighted. A constant flow of air through the habitat is necessary to remove the fumes produced by welding, but electrolysis and hydrogen formation is avoided because water is kept away from the arc. d. Underwater Cutting. Underwater cutting is used in salvage work and wherever cutting below the waterline is required on steel structures such as docks, piers, drilling platforms, and ships. The two most widely used methods are flame cutting and oxygen arc cutting. The technique used for underwater flame cutting is not too different from flame cutting steel in air. In each method, a fuel gas in a torch is mixed with oxygen and burned to produce a flame that preheats the steel, and a cutting jet is provided to supply oxygen to cut the steel. The underwater cutting torch, however, contains one important difference in construction. The underwater torch supplies its own ambient gas atmosphere, an air bubble around the flame, by means of compressed air that is ejected through a special nozzle surrounding the tip. An adjustable shield on the top of the torch is also usually supplied to help control the formation of the air bubble and to allow the torch to be held at the optimum distance from the work, even under conditions of poor visibility and constraint due to the cumbersome diving suits that must be worn. Slots are cut in the shield to allow gases to escape. The underwater torch is furnished with three hoses, for compressed air, oxygen, and fuel gas. Underwater flame cutting is most effective in severing a steelplate in the thickness range of 12.7 to 152 millimeters (1/2 to 6 inches). Below 12.7 millimeters, the quenching effect of the water retards the cutting action greatly. It is important that the air hose never be used for oxygen. Compressed air may contain some oil which can coat the hose causing an explosion when oxygen is introduced. Fuel gases are usually hydrogen or natural gas because these gases can be used at any depth without liquifying. Acetylene is almost never used in underwater cutting because at pressures more than 207 kilopascals (30 pounds per square inch) acetylene becomes unstable and may decompose violently even if no oxygen is present. A standard welding power source, capable of supplying 300 amperes of direct current straight polarity, is satisfactory for oxygen arc cutting under water. Electrode holders are fully insulated and of a special design so that both oxygen and current can he supplied to the electrode. To reduce resistance losses, cables should be size 2/0, except the last 3 meters (10 feet) at the torch which may he 1/0 for added flexibility. If the power source is more than 120 meters (400 feet) from the work, parallel cables of 1/0 or 2/0 are required. All underwater cable connections should be wrapped with rubber tape. A safety switch must be provided so that the torch is energized only while cutting. 217 Electrodes for underwater agxygen arc cutting are either tubular carbor- undum or steel. Steel electrades are availahle in 4.75- and 7.93-millimeter (3/16 and 5/16 inch) diameters with a 1.6-millimeter-diameter (1/16 inch) bore. These electrades are provided with a waterproof coating, which serves as an insulator during cutting. Cutting underwater requires that positive pressure he maintained by the electrode against the metal being cut; whereas, in air, the electrode is dragged along the intended line of cut. Particular attention must be paid to safety. The power sources must be grounded to the tender and ground cables securely connected to the work. All parts of the power cables and torches must be fully insulated and periodically inspected. An operating disconnecting switch must be part of the cutting electrical circuit. To prevent possible explosions, enclosed spaces must be vented so that gases generated during cutting cannot accummulate. 3. Environmental Considerations. a. Exposure to Air. (1) General. In contrast to organic materials, sunlight exposure does not cause deterioration of metals. Under some conditions, however, sunlight can be a contributing factor in the stress corrosion cracking of some stainless steels. Stress corrosion cracking occurs where high stress accelerates corrosion along intercrystallince boundaries, leading to weakening of intercrystalline bonds and eventual cracking. Austenitic stainless steels, such as type 304, 316, 321, 347, and even 216, are susceptible to stress corrosion cracking when exposed simultaneously to heat, stress, chloride ion, and oxygen. Cold-worked materials are most susceptible; however, even annealed austenitic stainless steel contains some residual stresses from fabrication and can crack. Stress corrosion cracking is believed to be time dependent, but the exact threshold conditions for this phenomenon to occur have not been established. Process equipment constructed of austenitic stainless steel and hydrotested with seawater but not properly drained and flushed has been ruined by stress corrosion cracking where the only heat applied was the heat of the sun. (2) Effect of Severe Temperatures. At one time, harbor facilities were located only in the torrid or temperate zones. Many ships were built of riveted construction. Welded ships were constructed by fitting each plate individually in turn. World War II created a demand for cargo ships that only mass production techniques could meet. These techniques involved constructing large hull sections offsite, then moving them into position for welding together to complete the hull. Because alinement of the sections was not perfect, force was applied to obtain sufficient alinement for welding. Many of these ships broke in two in the North Atlantic. Investigations revealed that brittle failure was the cause of these losses. Today, knowledge of the relationship between notch toughness and brittle failure enables marine structures to be designed ta survive the most severe temperatures. Carbon and most alloy steels suffer a decrease in toughness as tempera- tures are reduced. When slow rates of loading are applied these materials exhibit increased tensile and yield strength with only a slight loss of elongation and reduction of area at reduced temperatures. When the load is 218 , rapidly applied, as in the Charpy impact test, the amount of energy absorbed’ during fracture decreases gradually as testing is performed at progressively lower temperatures until, at some temperature, the absorbed energy drops dramatically. This temperature is known as the nil ductility transformation (NDT) temperature, the temperature at which the specimen exhibits little ductility before fracture. The NDT temperature can be defined by Charpy V- notch testing as (1) the temperature at which a certain absorbed energy is attained, (2) the temperature at which 50 percent shear fracture is attained on the broken specimen, or (3) the temperature at which a certain lateral expansion is attained on the specimen opposite the notch. A common value for minimum absorbed energy at the NDT temperature for ordinary constructional steels is 20 newton meters (15 foot-pounds); however, acceptable impact values are often stated in ASTM or other material specifications. Complete procedures for conducting many mechanical tests on metals including impact tests are given in ASTM A370. Figure 48 presents a representative plot of absorbed energy versus temperature for Charpy V-notch tests on a typical carbon steel. pct. SHEAR E z > iu) a wW 2 ul -30 -20 TEMPERATURE °C Figure 48. Plot of Charpy V-notch test on a low carbon steel. Values obtained from Charpy V-notch testing cannot be directly used in engineering calculations for design. Notch toughness values become signifi- cant only when correlated with a particular type of structure in a particular service. These values are useful to compare different materials. The NDT temperature determined by Charpy V-notch testing has correlated rather well with temperatures at which service failures have occurred for components of the same steel. Factors affecting the notch toughness of a metal are as follows: (a) Chemical composition, (b) gas content, 219 (c) micrgstructure (e.g., size, shape and orientatiagn of grains, and grain boundaries of a structure), (d) grain size, (e) section size, (physical crass-section dimensions), (£) hot and cold working temperature, (g) method of fabrication, and (h) specimen orientation in relation to working directian. Figure 49 presents representative plots of Charpy V-notch absorbed energy curves for several materials used in construction. Fully killed carbon steel made using a fine grain melt practice in the normalized heat treatment has the best notch toughness at lower temperatures of the carbon steels. If sulfide shape control is used during processing, improved notch toughness can be obtained in the transverse (across grain) and through (with grain) section directions. Austenitic stainless steel, type 304, and 9- percent nickel are candidate materials for handling liquefied gases. Notice that gray cast iron exhibits little notch toughness at any temperature shown. (3) Wind Erosion. Wind erosion does not have a severe effect on metals. Wind-driven sand, however, can destory paint and therefore increase the formation of rusting on steel structures. Appearance is the property most often affected. b. Exposure to Flora. The major effect of flora on metals is a slight increase in corrosion rate where the plants, by their root system, may transport additional moisture to the metal surface. In some soils, aerobic bacteria are present that oxidize sulfur which is either present in the soil or is obtained from decaying organic matter. By oxidation of sulfur, a strong solution of sulphuric acid is formed that reacts with any basic material present. The presence of either anaerobic or aerobic bacteria can cause soils to be corrosive to metals even though a usual mineral analysis of the soil and water does not reveal that a corrosive condition exists. c. Exposure to Burrowing Animals. Most metals have high hardness which prevents burrowing animals from penetrating. Animals have damaged the insulation covering of some buried electrical cables, which resulted in failure of the cables. d. Exposure to Freshwater. (1) General. Exposed surfaces of metals are subject to some degree of corrosion from water. The corrasiveness of water is basically dependent on three factors; acidity, oxygen content, and electrical conductivity. Many rivers are polluted by industrial wastes or runoff from mines causing the water to become acid. Such water may be mare corrosive to carbon steel than seawater would be. Rainwater becomes slightly acid as it falls to earth due to saturation with carbon dioxide. As the rain contacts the earth it becomes altered by reaction with minerals and soil. Depending on the acidity and 220 KILLED FINE GRAIN NORMALIZED TYPE 304 SS SEMIKILLED RIMMED [ea] 4 I <= uw v= oO a uJ z uJ + ° 3- Yo%Ni ul (eo) Ni-RESIST TYPE D-2 fy, GREY CAST IRON a A Ls -300 -200 -100 0 +100 + 200 TEST TEMPERATURE Op Figure 49. Representative Charpy V-notch absorbed energy curves for several materials. (Data compiled from International Nickel Company, 1976, and American Society for Metals, 1978). mineral composition, stream water may be less corrosive to carbon steel than rainwater. (2) Water Penetration Effects. Metals are impervious to water penetration. (3) Freezing and Thawing. The volume expansion of ice in fine- grained soils, such as very fine sand, silt, or clay, may produce lateral thrusts to sheet-pile structures. Placement of free-draining coarse granular soil above the frostline behind sheet-pile walls should eliminate the possi- bility of lateral thrust from ice or frozen ground. Steel sheet piling can 22! yield laterally to relieve any thrust load due to ice. Plugged and broken waterlines caused by ice are inconveniences that require cooperation between design and construction personnel, and between operations and maintenance personnel to eliminate this problem. Heat tracing and insulation are solu- tions to this problem, but other methods may be more practical such as pumping out fire hydrants, and closing doors to heated loading docks. e. Exposure to Saltwater. (1) Corrosion Effects - General. Corrosion rates of metals in seawater are higher than in pure water because ions of halogen compounds, such as sodium chloride, have the power to cause localized breakdown of oxide films that are responsible for passivity and corrosion resistance. Halogen ions can form soluble acidic corrosion products, such as ferric chloride, which interfere with the restoration of passivity to steel leading to localized corrosion in the form of pitting. Tests have shown that corrosion rates for carbon steel in the atmosphere at the shoreline are 10 times the rates shown by plates 460 meters (500 yards) from the shoreline. It has been shown that the rate of corrosion of steel in seawater and in freshwater is governed to a large extent by the oxygen content. Carbon steel, in contact with freshwater saturated with oxygen at ambient tempera- ture, usually exhibits a corrosion rate of 220 micrometers (9 mils) per year general corrosion plus an additional 220 micrometers per year of pitting. When freshwater is oxygen-free, the corrosion rate for carbon steel is usually only 25 micrometers (1 mil) per year or less, provided no corrosive pollutants are present. (2) Variable Oxygen Content. The pattern of corrosion found on steel pilings in the atmosphere, the splash zone, the tidal zone, submerged in clean seawater, and in the mud zone varies considerably. A principal variable related to position is the oxygen content. The high corrosion rate in the splash zone is attributed to the constant wetting of the steel by highly aerated seawater. In the tidal zone, differential aeration produces a protective cell effect, resulting in a considerably lower corrosion rate. At deeper positions, less oxygen is present and the corrosion rate for steel drops to rates usually in the range of 76 to 152 micrometers (3 to 6 mils) per year. Carbon steel in seawater that has been treated to remove dissolved oxygen and marine bacteria exhibits an even lower corrosion rate under low velocities. Austenitic stainless steel and aluminum alloys exhibit satisfactory corrosion resistance in the splash zone, because the high oxygen content helps keep passivating films intact. Aluminum has better corrosion resis- tance in the splash zone than at greater depths where less oxygen is present. The high corrosion rates on carbon steel piling in the splash zone may also be attributed to the severe electrochemical corrosion cells set up in the pile. Piles made from high-copper-hearing, high-strength, low-alloy steel conforming to ASTM Standard A690 haye two to three times the resistance to seawater corrosion in the splash zone of ordinary carbon steel, although such steels exhibit no better corrosion resistance at greater depths. (3) Effects of Polluted Seawater. Polluted waters often contain hydrogen sulfide which causes severe effects in metals sensitive to the 222 effects of sulfides. Hardened steel, or welds not stress relieved in medium carbon steel, may crack due to stress corrosion. Hydrogen sulfide presence can lead to corrosion of the vapor side of copper alloy heat exchangers. Small amounts of ammonia may also be present in polluted seawater, causing aggressive attack and stress corrosion cracking of copper-zinc alloys. The copper-nickel alloys are preferred when ammonia pollution is expected and the 90-10 copper nickel alloy (UNS No. C70600) has demonstrated satisfactory performance in many applications where sulfide pollution has been present. f. Effects of Marine Organisms. Biofouling and biological fouling are common terms that refer to the settlement and growth of living organisms on materials exposed to the marine environment. Some metals, such as titanium and the nickel-chromium-high molybdenum alloys, are completely corrosion resistant under fouling. Copper base alloys exhibit varying degrees of resistance to biofouling. Other materials such as aluminum, carbon steel, and stainless steel both foul and suffer increased corrosion due to bio- fouling. On structures such as wharves and breakwaters, biofouling may not be of as much importance. However, biofouling causes increased wave action loadings on such structures. Increased flow blockage and decreased heat transfer efficiency are other problems encountered as result of marine biofouling on metal structures in marine service. Biofouling resistance is highest for copper and the 90-10 copper nickel alloy. Brass and bronze have good resistance but 70-30 copper nickel alloy, aluminum bronze, zinc (galvanizing), and Monel alloy 400 have only fair biofouling resistance. The high resistance to biofouling of many of the copper-base materials have been attributed by some researchers to the in- hospitable nature of the green cupric hydroxychloride corrosion product that forms on these materials. This film is itself loosely attached so that any marine organisms that do attach to this film are soon removed. Monel, carbon steel, aluminum, and stainless steel exhibit poor corrosion resistance under biofouling. Carbon steel suffers general corrosion, whereas Monel, aluminum, and stainless steel exhibit pitting and crevice corrosion. Crevice corrosion is caused by differential oxygen cells produced when oxygen is prevented from reaching the metal surface under barnacles. Corrosion rates on carbon steel may be reduced a little when biofouling is present due to reduced velocity of water at the metal surface; however, corrosion rates remain relatively high. Biofouling will periodically slough off when the corrosion product breaks off. The high general corrosion rate of carbon steel in seawater is attributed to marine organisms known as anaerobic bacteria. Principal groups are the sulphate-reducing and the iron-consuming bacteria. The sulphate-reducing bacteria require oxygen, which is derived from the reduction of compounds such as sulphates, sulphites, thiosulphates, or organic substances rather than dissolved oxygen. These bacteria liberate hydrogen sulphite which attacks iron severely, removing hydrogen from the cathodic areas of the steel with the formation of iron sulphide. The iron-consuming bacteria do not actually consume iron as food but do require iron in solution for growth. Biofouling has been controlled by using copper base alloys, antifouling coatings, mechanical cleaning of the surface, or environmental controls. Environmental control measures include increased flow velocity, elevated 223 temperature, and chlorination. When employing such control measures, the corrosion performance af the base metals must he considered. In addition to hiofouling, there are several organisms (such as limnoria, teredo, and termites) common in the marine environment that cause deteriora- tion of structures through boring. Because metal structures are impenetrable these organisms do not cause deterioration usually found on marine pilings constructed of wood. g. Wave and Current Effects. Fouling diminishes as water velocities in contact with a structure reach the l- to 2-meter-per-minute (3 to 6 foot) range. Pitting of the more noble materials slows down and may even cease. As velocities continue to increase, stainless steel and nickel base materials remain passive and inert but corrosion barriers are stripped away from carbon steel and copper alloys. Although wave or current velocity are seldom too high to allow the use of carbon steel, velocity is a factor to consider in the design of equipment such as piping and pumps. h. Abrasion. Abrasion to metal structures is caused by the movement of the elements in the coastal zone and their ability to transport particles with force against all structures. Significant particle transport is caused by wind and water. Structures in windswept beaches and shores are subject to severe abrasion from the wind-driven sand with substantial force and can result in significant metal wear in the case of steel or other metal structures. For steel pile structures, abrasion to piles at the mud line increases the metal loss far in excess of loss from corrosion. For some structures, usually on land or for structural elements located above the waterline in the ocean, added abrasion resistance can be provided by addi- tional protection in the form of concrete, wood, or hard-surfaced alloys Most hard-surfaced metals require special heat treating and the addition of small amounts of other elements such as manganese. The latest improvement in steel piling was the development of mariner steel for seawater exposure. Mariner steel was developed primarily to improve the corrosion resistance of steel in seawater by alloying about 0.5 percent each of copper and nickel in addition to about 0.1 percent of phos- phorous (ASTM Standard Specification A 690-77). While mariner steel has a somewhat improved strength, its hardness is little different than that of normal steel piling and abrasion resistance is also little different. Although cathodically protected steel structures in seawater usually take on a calcareous coating (chemicals deposited from the seawater) this coating is too soft to offer any resistance to abrasion. i. Seismic Effects. Metals are well suited for marine construction in areas of seismic activity. They possess high tensile strength, good duc- tility, and, when properly specified, good toughness. Jn addition, metals can consistently meet specified minimum seismic requirements. Steel, the most economical of the metals for construction of harbor facilities, is available in several shapes. The inherent high-bending strength of steel H- piles permits the development of required resistance to lateral forces, when used in foundation designs where resistance. to seismic forces is required. The ability of metals to be loaded in shear, compression or tension within calculated limits facilitates the design of earthquake-proof structures. 224 j. Fire. Metals in the shapes and sizes used in construction will not burn in a fire; however, these do have reduced strength as temperatures rise. Carbon steel is affected above 340° Celsius (650° Fahrenheit). At 480° Celsius (900° Fahrenheit), carbon steel has only about half the strength that it does at room temperature. During a fire, structures of all steel construction have collapsed. Structures are protected from fire loss by the installation of sprinkler systems, which spray water on the building and roof supports to keep them cool and by the covering of steel beams and supports with concrete to provide insulation. Metals that have experienced a fire should be tested for suitability before being reused because strength and toughness may be reduced. Heat treatment may be required to restore properties. k. Human Activity. Accidents and theft are two elements of human activity that the designer must consider. Piers and wharves are constructed with fender systems to minimize damage from impact by ships. When accidents do cause damage, metal structures may be repairable by welding. Legs on drilling platforms are often sheathed with copper nickel alloys in the splash zone areas to minimize corrosion. Attempts to use similar methods in harbors have not been completely successful because the sheathings have been stolen for their metal value as scrap. 4. Uses of Structural and Sheet Metal. a. General. (1) Steel. Various parts of coastal structures are made of steel. Steel H-piles or pipe piles are used to support foundations. Steel H-piles are used in preference to steel pipe piles because they are more easily driven in soils containing hard strata or obstructions such as boulders. Steel H-piles are easily spliced by welding, allowing driving to deep rock strata if necessary. Steel H-piles are also frequently used to support fender systems immediately in front of the wharves. Steel bolts are used to attach rubber bumpers to the fender system that prevents damage to the structure by absorbing the ship impact loads. Cast-steel bollards and mooring posts are used to take up ships' lines. Steel is an ideal material for breasting and mooring dolphins because steel can be easily jointed, has high tensile strength, good ductility, and good toughness. Structural steel shapes are used for framing of structures. Even the fences around coastal installations are most often chain-link steel fences. Large quantities of steel are used in components that appear to be all concrete. Concrete piles, beams, structure foundations, walls, roadways, and pads all will contain steel reinforcing bar, wire or wire fabric. Materials for concrete reinforcement are covered in Section V, Portland Cement Concrete. (2) Aluminum. Many alloys of aluminum possess high corrosion resistance to marine atmospheres as well as good strength-to-weight ratios. These properties make aluminum an economic choice for many applications in coastal structures, particularly where freedom from maintenance is desired. 225 Pa In buildings, door and window frames are usually 6063 aluminum, roofing and siding, alclad 3004 aluminum. Tread plate, such as used for decking and catwalks, is 6061 aluminum heat treated to T4, T42, or T6 temper. Aluminum alloys are also used for architectural trim, hardware, and gutters and downspouts. Insulation is even faced with aluminum foil to reflect heat, making the insulation more effective. Electrical wire and bus bars are either copper or 1350 aluminum. Because the conductivity of 1350 aluminum is approximately one half that of copper, the cross section of the aluminum conductor must be approximately twice that of the copper for equivalent current capacity. The specific gravity of aluminum is so much less than that of copper that equivalent conductors of 1350 aluminum weigh only half those of copper, making the choice one of economics. Lamp poles and standards are made from 6063 aluminum. Even the lamp bases may be 3004 or 5050 aluminum, Tanks and equipment for liquid natural gas facilities must be constructed of materials having high notch toughness. Aluminum alloys 5083 and 5456 have been specified for liquid natural gas storage tanks and vaporizers because these alloys have good corrosion resistance to marine atmospheres and high notch toughness. In accordance with ASTM A370, aluminum alloys do not require Charpy impact testing because aluminum alloys do not become brittle at cryogenic temperatures. (3) Copper. Electrical conductors such as wire and bus bars are the largest applications of copper. Copper is also used for pipe and sheathing. Coppers are used in many hidden applications in supporting equipment at coastal structures. Such uses include radiators in air conditioners and powered equipment, springs and contacts in communication and control systems, and even tools of beryllium copper for use in areas where sparks must be prevented to avoid fires and explosions. Copper alloys are used in equipment such as heat exchangers, pumps, valves, and hardware for sluice gates and traveling water screens. (4) Nickel. Nickel base alloys have good corrosion resistance to seawater and generally high resistance to cavitation damage. Most resistant are nickel-chromium-molybdenum columbium alloy 625 (Inconel 625, produced by Huntington Alloys, Huntington, West Virginia) and nickel-molybdenum-chromium alloy C (Hastelloy UC, produced by Stellite Division, Cabot Corporation, Kokomo, Indiana). These two alloys are used for springs, cable connectors, bellows- type expansion joints, rupture disks, and pump seal rings in coastal facili- CLES 5 Nickel-copper alloy 400 (Monel 400, produced by Huntington Alloys) is the lowest cost nickel base alloy for marine service. This alloy is used for valve and pump trim, fasteners, heat exchangers, and piping. (5) Titanium. The major uses of titanium in coastal structures are steam condensers employing seawater cooling, ball valves, and desalination equipment. Titanium will tolerate polluted seawater under conditions where other materials fail. As a result, many coastal powerplants are installing steam condensers using titanium tubes. 226 b. Sheet-Pile Structures. (1) Design. Bulkheads in waterfront facilities are subjected to lateral pressure resulting from earth movement and the unbalanced hydrostatic and seepage forces acting on opposite sides of the wall. A higher water level may exist in the backfill behind the wall than in front of it as a result of a receding tide, receding high water, or a heavy rainstorm. Other lateral loads that may be encountered are ice thrust, wave forces, ship impact, mooring pull, and earthquake forces. Because of its material strength sheet pile is often used in marine construction for bulkheads. The designer, after evaluating the lateral pressure and forces, must determine the required depth of piling penetration, the maximum bending moments in the piling, and the maximum bending stresses in the wall. An appropriate sheet- pile section must be selected, taking into account yield strength and moment of inertia of the selected section. Some typical steel sheet-pile profiles are shown in Figure 50. A choice may be made between a cantilevered or anchored wall. Anchored sheet-pile walls can be designed for greater height than is possible with the cantilever-type design with a similar sheet-pile section. For heights to about 11 meters (35 feet) (depending on soil conditions), sufficient support can be obtained from anchor tie rods near the top of the wall and the lateral support of the embedded part of the wall.. For greater heights, higher yield strength steel or multiple tie rods at lower levels are required. Anchorage systems in use include deadman anchors, H-pile anchors, and sheet-pile anchors. Sketches of the systems are shown in Figure 51. Regardless which anchorage system is used, the anchor must be located outside the potential active fracture zone behind the sheet-pile wall. Passive resistance of the anchor is not possible if the ground is unstable. A complete sheet-pile wall system may consist of the wall, wale, tie rods, and the anchor. The wale is a flexible member attached to the wall which distributes the horizontal reactive force from the anchor tie rods to the wall section. Locating the wale on the outside of the wall where the piling will bear against the wale in compression is preferred for engineering purposes. However, wales are sometimes bolted onto the inside face to provide a clear outside face. Wales are often constructed of steel structural channels conforming to ASTM Standard A36 mounted with their webs back to back, and separated by enough space to clear the end of tie rod between them. When the wales are located on the inside face, each sheet-pile section is bolted to the wale. Standard wale designs for wales located on both outside and inside faces are shown in Figure 52. Tie rods are usually round steel bars, comforming to ASTM Standard A36, that have been upset and threaded at each end so as to maintain cross- sectional area in the threaded part. Usually a turnbuckle is used between two tie-rod sections ta allow removal of slack. Sagging of the tie rods may occur because of soil settlement around them which drags them downward, causing increased tension in the rods. Two methods of avoiding this con- dition are: (1) use light vertical piles at 6- to 9-meter (20 to 30 foot) intervals to support the rods, or (2) encasing the rods in large conduits. Zein eerie eerie ee eee eae /) Y (Liltiblilitl lille Figure 50. Typical steel sheet-pile profiles -- top view, straight; middle view, arch, bottom view, angle. 228 REINFORCED CONCRETE CAP (CONTINUOUS) STEEL H-PILES \e (VARIABLE) PILING TIE ROOS & DEAD MAN TIE RODS & A-FRAME USING STEEL H—PILES Figure 51. Typical-steel pile anchorage systems. DOUBLE CHANNEL OUTSIDE WALL DOUBLE CHANNEL INSIDE WALL Figure 52. Standard wale designs. 229 Tie rods are subject to corrosion and must, therefore, be adequately coated and wrapped. (2) Construction. Steam hammers are commonly employed for pile driving in the United States. During driving, the steam hammer, consisting of a housing and the moving part called the ram rests on top of the pile. A single acting steam hammer is a freely falling ram with steam pressure acting on a piston to raise the ram prior to fall. In a double acting hammer, steam is not only used to lift the ram but also to help drive the ram dgwnward. Double acting hammers are able ta deliver blows faster than single acting hammers of the same energy output because double acting hammers use a shorter stroke and higher ram acceleration. Both drop hammers and diesel hammers are also available. A drop hammer consists of a heavy weight or ram that is allowed to fall by gravity on top of the pile. Fall height must be controlled to avoid damage to pile heads by excessive impact from rams moving with high velocity. Excessive impact or improper cushioning during pile driving may result in mashed pile heads. Vertical misalinement of the pile as a result of obstructions encountered below the ground surface or of poor pile-driving conditions may cause failure of pile interlocks. If excessive misalinement occurs, sheet piles can become over stressed resulting in bulkhead failure. The method used for the construction of steel breakwaters depends on the soil conditions and the height of the waves. If the waves are below 10 feet, and the bottom is soft to a great depth, steel sheet pile topped with concrete and supported with batter piles may be used. Bulkheads for small-boat harbors have been constructed using sheet piling of aluminum alloy 5052-H141. Coping was of 6063-T6, tie rods and stiffener bar beams of 6061-T6. Deadman anchors were constructed of 5052- H141 alloy. Aluminum sheet pile is available in 3.6-meter (12 foot) lengths which limit application to shallow facilities. c. Gabions. Gabions, compartmented rectangular containers made of galvanized steel hexagonal wire mesh and filled with small stones, have been used to reinforce the shoulder of seawalls constructed of rock. They have also been used to construct jetties as well as revetments and seawalls to control shoreline erosion. Gabion mattresses can also be used as foundations or filter layers under rubble-mound structures and caisson structures. For seawater use, gabions of galvanized wire should be coated with plastic to reduce corrosion. The Alaska District limits use of gabions in the wave zone where ice occurs due to bursting of the gabions by the ice. Also, if the gabions are not rigidly filled, the rockfilling can move and abrade the wire. 230 VIII. WOOD 1. .General. Wood is widely used in the coastal zone because it is strong, resilient, and easily installed with common tools and equipment. It is also a common material available nearly everwhere at a reasonable cost. When properly treated, it is very durable. Its ability to absorb energy (resiliency) is a feature that makes it especially desirable for uses such as fender piles. The main problem when using wood in the coastal zone is that it is an organic material that is the natural food supply and habitat for fungi, bacteria, insects and marine organisms. The first three occur on land and are more active in the high moisture conditions at the coast. Wood treat- ments to prevent attack by natural enemies are very effective in combating damage from these sources. 2. Physical Properties of Wood. a. Physical Structure of Wood. Wood is a cellular organic material made up principally of cellulose, which comprises the structural units, and lignin, which cements the structural units together. It also contains certain extractives and ash-forming minerals. Wood cells are hollow and vary from about 1 000 to 8 000 micrometers (40 to 330 mils) in length, and from 10 to 80 micrometers (0.4 to 3.3 mils) in diameter. Most cells are elongated and are oriented vertically in the growing tree, but some, called rays, are oriented horizontally and extend from the bark toward the center, Orepach) On nthemtnee. (1) Hardwoods and Softwoods. Species of trees are divided into two classes: hardwoods, which have broad leaves; and softwoods or conifers, which have needlelike or scalelike leaves. Hardwoods shed their leaves at the end of each growing season, but most softwoods are evergreens. The terms "hardwood" and "'softwood" are often misleading because they do not directly indicate the hardness or softness of wood. In fact, there are hardwoods which are softer than certain softwoods. (2) Heartwood and Sapwood. Several distinct zones are distinguish- able in the cross section of a log: the bark; a light-colored zone called sapwood; an inner zone, generally of darker color, called heartwood; and, at the center, the pith (Fig. 53). A tree increases in diameter by adding new layers of cells from the pith outward. For a time, this new layer contains living cells which produce sap and store food, but eventually, as the tree increases in diameter, cells toward the center become inactive and serve only as support for the tree. The inactive inner layer is the heartwood; the outer layer containing living cells is the sapwood. There is no consistent difference between the weight and strength properties of heartwood and sapwood. Heartwood, however, is more resistant to decay fungi than is sapwood, although there is a great range in the durability of heartwood from various species. (3) Annual Rings. In climates where temperature limits the growing season of a tree, each annual increment of growth usually is 231 Figure 53. Typical cross section of a log. readily distinguishable. Such an increment is known as an annual growth ring or annual ring, and consists of an earlywood and a latewood band. (4) Earlywood (Springwood) and Latewood (Summerwood). In many woods, large thin-walled cells are formed in the spring when growth is greatest, whereas smaller, thicker walled cells are formed later in the year. The areas of fast growth are called earlywood, and the areas of slower growth, latewood. In annual rings, the inner, lighter colored area is the earlywood, and the outer, darker layer is the latewood. Latewood contains more solid wood substance than does earlywood and, therefore, is denser and stronger. The proportion of width of latewood to width of annual ring is sometimes used as one of the visual measures of the quality and strength of wood. (5) Grain and Texture. The terms "grain" and "texture" are used in many ways to describe the characteristics of wood and, in fact, do not have a definite meaning. Grain often refers to the width of the annual rings, as in "close-grained" or "coarse-grained." Sometimes it indicates whether the fibers are parallel to or at an angle with the sides of the pieces, as in "straight-grained" or "cross-grained." Texture usually refers to the fineness of wood structure rather than to the annual rings. When these terms are used in connection with wood, the meaning intended should be defined. b. Moisture Content of Wood. Wood may contain moisture as "free water" in the cell cavities and as "absorbed water" in the capillaries of the cell walls. When green wood begins to lose moisture in the seasoning process, the 232 , cell walls remain saturated until the free water has been evaporated. The point at which evaporation of free water is complete and cell walls begin to lose their moisture is called the fiber saturation point (fsp). This point occurs between 25 and 30 percent moisture for most species. Moisture in wood is expressed as a percentage of the ovendry weight and is determined most accurately by weighing a representative sample, drying it at slightly more than 100 Celsius @ize Fahrenheit), until no further loss of weight takes place, reweighing, and then dividing the difference between the original and final weights by the final (ovendry) weight. Electric moisture meters offer a simpler though less exact method of determining moisture content. With slight seasonal variations, wood in use over a period of time attains an equilibrium moisture content (emc) corres- ponding to the humidity and temperature of the surrounding atmosphere. When exposed to similar atmospheric conditions, different woods will have the same moisture content regardless of their density. Moisture content has an important effect upon susceptibility to decay. Most decay fungi require a moisture content above fiber saturation point to develop. In addition, a favorable temperature, an adequate supply of air, and a source of food are essential. Wood that is continuously water-soaked (as when submerged) or continuously dry (with a moisture content of 20 percent or less) will not decay. Moisture content variations above the fiber saturation point have no effect upon the volume or strength of wood. As wood dries below the fiber saturation point and begins to lose moisture from the cell walls, shrinkage begins and strength increases. c. Directional Properties. Wood is not isotropic because of the orientation of its cells and the manner in which it increases in diameter. It has different mechanical properties with respect to its three principal axes of symmetry: longitudinal (parallel to grain), radial (perpendicular to grain), and tangential (perpendicular to grain) (see Fig. 54). Strength and elastic properties corresponding to these three axes may be used in design. The difference between properties in the radial and tangential directions is seldom of practical importance in most structural designs; for structural purposes it is sufficient to differentiate only between properties parallel and perpendicular to the grain. d. Specific Gravity. Solid wood substance is heavier than water, its specific gravity being about 1.5 regardless of the species of wood. Despite this fact, dry wood of most species floats in water because a part of its volume is occupied by air-filled cell cavities. Variation among species in the size of cells and in the thickness of cell walls affects the amount of solid wood substance present and hence, the specific gravity. Thus, specific gravity of wood is a measure of its solid wood substance and an index of its strength properties. Specific gravity values, however, may be somewhat affected by gums, resins, and extractives which contribute little to strength. The relationship of specific gravity to wood strength is recommended in the practice of assigning higher basic stress values to lumber designated as "dense."' e. Dimensional Stability. (1) Effect of Temperature. Wood, like most other solids, expands on heating and contracts on cooling. In most structural designs, the 233 Figure 54. The principal axes of wood: L, longitu- dinal; R, radial; T, tangential (American Institute Timber Construction, 1974). increase of wood in length due to a rise in temperature is negligible, and, as a result, the secondary stresses due to temperature changes may, in most cases, be neglected. This increase in length is important only in certain structures that are subjected to considerable temperature changes, or in members with very long spans. é The increase in length per unit of length for a rise in temperature of 1° is designated the coefficient of linear thermal expansion. It differs in the three structural directions of wood. Radially and tangentially (perpen- dicular to grain), the coefficient of linear thermal expansion varies directly with the specific gravity of the species. It is in the range of 45 x 10© meters per meter per ° Celsius (25 x 10° feet per foot per Fahrenheit) times specific gravity for a dense hardwood such as sugar maple to 81 x 10® meters per meter per ° Celsius (45 x 10° feet per foot per Fahrenheit) times specific gravity for softwoods such as Douglas fir, Sitka spruce, redwood, and white fir. Radial or tangential dimensional changes for common sizes of wood structural members are relatively small. Longitudinally (parallel to grain), the coefficient is independent of SUSEEEIS (RENIN and varies from 3.08 x 10° meters per meter per ° Celsius (1.7 x 10° feet per foot per Fahrenheit) to 4.5 x 10° meters per meter per ° Celsius (2.5 x 10®© feet per foot per ° Fahrenheit) for different species. This is from one-tenth to one-third of the values for other common structural materials and glass. For this reason, consideration must be given to the different thermal expansion coefficients of various materials used in conjunction with wood. The average coefficient of linear thermal expansion for plywood is 6.12 x 10° meters per meter per ° Celsius (3.4 x 10° feet per foot per Fahrenheit). The coefficient of thermal expansion for thickness is essentially the same as for solid lumber. (2) Effect of Moisture Content. Between zero moisture content and the fiber saturation point, wood shrinks as it loses moisture and swells as 234 it absorbs moisture. Above the fiber saturation point there is no dimen- sional change with variation in moisture content. The amount of shrinkage and swelling differs in the tangential, radial, and longitudinal dimensions of the piece. Engineering design should consider shrinkage and swelling in the detailing and use of lumber. Shrinkage occurs when the moisture content is reduced to a value below the fiber saturation point (for purposes of dimensional change, commonly assumed to be 30 percent of the moisture content at the fiber saturation point) and is proportional to the amount of moisture lost below this point. Swelling occurs when the moisture content is increased until the fiber saturation point is reached, then, the increase ceases. For each 1 percent decrease in moisture content below the fiber saturation point, wood shrinks about one-thirtieth of the total possible shrinkage, and, for each 1 percent increase in moisture content, the piece swells about one-thirtieth of the total possible swelling. The total swelling is equal numerically to the total shrinkage. Shrinking and swelling are expressed as percentages based on the green wood dimensions. Wood shrinks most in a direction tangent to the annual growth rings, and somewhat less in the radial direction, or across these rings. In general, shrinkage is greater in heavier pieces than in lighter pieces of the same species, and greater in hardwoods than in softwoods. As a piece of green or wet wood dries, the outer parts are reduced to a moisture content below the fiber saturation point much sooner than are the inner parts. Thus the whole piece may show some shrinkage before the average moisture content reaches the fiber saturation point. Neither the initial nor the final moisture content (M. or M,) can be greater than 30 percent when calculating shrinkage becausé that is the moisture content at which, when drying, wood starts to shrink or at which, when absorbing moisture, it reaches its maximum dimension. Values for longitudinal shrinkage with a change in moisture content are ordinarily negligible. The total longitudinal shrinkage of normal species from fiber saturation to ovendry condition usually ranges from 0.1 to 0.3 percent of the green wood dimension. Abnormal longitudinal shrinkage may occur in compression wood, wood with steep slope of grain, and exceptionally lightweight wood of any species. The cross-laminated construction of plywood gives it relatively good dimensional stability in its plane. The average coefficient of hydroscopic expansion (or contraction) is about 0.000 2 meter per meter (0.000 2 foot per foot) of length or width for each 10 percent change in relative humidity, or 0.2 percent ovendry to complete saturation. 3. Mechanical Properties of Wood. a. Wood as Structural Material. Wood is not an isotropic material because strength properties differ along its different axes. It is strongest when loaded in induce stress parallel to grain, either in tension or compression. However, this condition is not always possible and loading perpendicular to grain may be accomplished in a satisfactory manner. 235 The anisotropic nature of wood may be confusing to the designer during his first experience with its use, but as he gets to know the material he finds that engineering design with wood can be interesting as well as productive in the way of lower construction costs. The discussion which follows provides a brief description of the various mechanical properties of structural wood as they affect engineering design. (1) Tension Parallel to Grain. A force generating tension parallel to grain, as shown in Figure 55, creates a tendency to elongate the wood fibers and to cause them to slip by each other. Resistance to tension applied strictly parallel to grain is the highest strength property of wood. This resistance, however, is substantially reduced when the force is applied at an angle to the grain or when the cross section of the piece is reduced by knots or holes. Figure 55. Tension parallel to grain. (2) Tension Perpendicular to Grain. A force generating tension perpendicular to grain tends to separate the wood fibers along the grain. This is the direction in which wood has the least strength, and because it is not good practice to apply loading to induce tension across grain, design values are not provided for this strength property, except for special applications. (3) Compression Parallel to Grain. A force generating compression parallel to grain, as shown in Figure 56, creates a tendency to compress the wood fibers in the lengthwise position. As with tension, resistance to compression parallel to grain is affected by the angle of load to grain and by the presence of knots or holes. (4) Compression Perpendicular to Grain. A force applied perpen- dicular to grain, such as the bearing under the ends of a beam as shown in Figure 57, tends to compress the wood at its surface. While the wood becomes more dense as it is compressed, this action causes slight displacement of the supported member. Thus, limits are placed on loading in bearing perpen- dicular to grain. (5S) Shear Parallel to Grain. A force applied in the manner illustrated in Figure 58 causes one section of the piece to shear or slide along the other section in a direction parallel to grain. In a loaded beam where the induced stress on the one side is compression and on the other side is tension, as illustrated in Figure 58, shearing stress is created 236 <4 —=— GRAIN —_ = > Figure 56. Compression parallel to grain. Figure 57. Compression perpendicular to grain. X Figure 58. Shear parallel to grain. parallel to grain. The largest shear stress parallel to grain usually occurs along the neutral axis on the plane at which the induced stress changes from compression to tension and generally increases to the maximum at the supports or end of the beam. Shakes, checks, and splits, which may occur during the drying of lumber, have the effect of reducing the area in the plane of shear resistance. Consequently, laboratory test values for shear strength parallel to grain are substantially reduced for design purposes in order to accommodate the probability of the occurrence of shakes, checks and splits after drying. 237 (6) Shear Perpendicular to Grain. Shear perpendicular to grain is not a design factor in solid wood because effective control is applied through limits on design stresses in shear parallel to grain and compression or bearing perpendicular to grain. (7) Fiber Stress in Bending. A force or set of forces applied perpendicular to a beam, as shown in Figure 59, creates compression in the fibers on the side to which the force is applied and it also creates tension in the fibers on the opposite side. Thus, there is a tendency to compress the fibers on the compression side and to elongate the fibers on the tension side. As the stress is distributed from the extreme fibers or outside faces toward the center or neutral axis of the piece it is reduced in intensity. Thus, deviations in slope of grain and the presence of knots or holes in these outside faces tend to reduce the resistance in the extreme fibers and the bending strength of the beam. COMPRESSION £ TENSION Figure 59. Fiber stress in bending. (8) Proportional Limit, Static Bending. The proportional limit occurs at the point where the induced strain or deformation ceases to be proportional to the stress or applied load, as determined by the standard test method. Stress at proportional limit is computed by the standard method. All conventional methods of structural design for wood are within the proportional or elastic limit. (9) Modulus of Rupture, Static Bending. The modulus of rupture is computed from the ultimate load or the point at which the piece breaks under the standard bending test method. Loading by test beyond the proportional limit shows an increasing rate of deformation, without a specific yield point, until ultimate load is reached. (10) Modulus of Elasticity, Static Bending. The modulus of elas- ticity is a measure of stiffness and is computed on the basis of the load and deformation within the proportional limit. b. Design Values For Structural Lumber. (1) General. Design values are assigned to lumber in a scientific manner to provide material of predictable strength properties to meet the requirements of engineering design. Because of the varying nature of the different species of trees, there is a wide range of stress values from which the designer can make his selection. However, to avoid delay during 238 / construction, it is advisable to determine which species and grades are available locally before design values are selected. (2) Classification of Structural Lumber. Because the effects of knots, slope of grain, checks, and shakes on the strength of lumber vary with the loading to which the piece is subjected, structural lumber is often classified according to its size and use. The three major classifications are as follows: (a) Dimension lumber--pieces of rectangular or square cross section, 2 to 4 inches thick and 2 inches or more wide (nominal dimensions) graded primarily for strength in bending edgewise or flatwise but also used where tensile or compressive strength is important; dimension lumber may be further classified as joists and planks, for material 5 inches or more in nominal width, and as light framing or structural light framing for material 2 to 4 inches wide; (b) beams and stringers--pieces of rectangular cross section, 5 to 8 inches (nominal dimensions) and larger, graded for strength in bending when loaded on the narrow face; and (c) posts and timbers--pieces of square or nearly square cross section, at least 5 by 5 inches (nominal dimensions) and graded primarily for use as posts or columns but adapted to miscellaneous uses in which bending strength is not especially important. (3) Characteristics Affecting Strength. Aside from the natural properties of the species, the major characteristics affecting the strength of a piece of lumber are the sizes of knots or holes and their locations, the sizes of checks or shakes and splits and their locations, the amount of wane or absence of wood, slope of grain, degree of density or rings per inch, and the condition of seasoning. All these characteristics are taken into consideration in the stress grading of a piece of lumber. These conditions are illustrated in Figure 60. (4) ASTM Standards. There are two ASTM standards which serve as principal references in the assignment of working stresses of lumber. One standard is ASTM D2555, "Methods for Establishing Clear Wood Strength Values,'' which sets forth procedures for establishing strength values for clear wood of different species in the unseasoned condition and unadjusted for end use. Such procedures may be applied to a single species or to a group of species where growth and marketing conditions justify such grouping. The other standard is ASTM D245, "Methods for Establishing Structural Grades for Visually Graded Lumber," which sets forth reduction factors to be applied to the clear wood values and provides procedures for determining strength ratios, based on knots and other characteristics, which, when applied to the adjusted clear wood values, results in working stresses for the various commercial grades of any species. This standard also provides adjustments for degree of density and for condition of seasoning. (5) Lumber Grading Rules. Lumber grading rules are, in effect, specifications of quality. In the rules the maximum knots, slope of grain 239 ICHEVER WHE LEAST DIMENSION SHAKES E- MEASURE BETWEEN LINES F- MEASURE LEAST DIMENSION PARALLEL TO THE EDGES G- MEASURE ALONG CORNER OR F—-MEASURE LEAST DIMENSION MEASURE SIZE MOST NEARLY REPRESENTING DIAMETER OF BRANCH CAUSING THE KNOT KNOTS Figure 60. Defects affecting strength of lumber (American Institute Timber Construction, 1974). 240 , and other strength reducing characteristics are described in sufficient detail that the procedures of ASTM D245 can be applied and working stresses can be assigned to the specified quality. It is common practice to give each grade a commercial designation such as No. 1 for best, No. 2 for next best. This means that the purchaser orders the commercial grade which qualifies for the values used in design. (6) Machine Graded Lumber. While most structural lumber has design values assigned on the basis of visual grading to meet a minimum quality specification, there is a growing trend toward the nondestructive testing of lumber by machine. In this method a piece of lumber is passed flatwise through a series of loading rollers and the stiffness, or modulus of elasticity, is automatically recorded. Through correlation with pre- viously established test data, bending strength and other strength properties are assigned to each piece tested. At present, machine grading is supple- mented by visual grading particularly in the assignment of horizontal or longitudinal shear values. (7) National Design Specification. The principal reference for working stresses for commercial grades of structural lumber is the National Design Specification for Wood Construction, available from the National Forest Products Association, Washington, D.C. The design value information in this specification is taken from the published rules written by the American Lumber Standards Committee (ALSC) and other grading rules writing agencies. When these values are used, each piece of lumber is required to be identified by the grade mark of a lumber grading or inspection agency recognized as being competent. The National Design Specification provides for design of single member uses of lumber and other structural timbers, and also for repetitive member uses of lumber where load sharing is known to exist between repetitive framing members which are spaced not more than 0.6 meter (24 inches), are not less than 3 in number and are joined by floor, roof, or other load- distributing elements adequate to support the design load. For repetitive member uses, the design values in bending are higher than those for single member uses, as provided in the National Design Specification. 4. Selection of Timber Piles. a. Round Timber Piles. Recommendations for the use of timber piles in foundations may be found in the American Wood Preservers Institute (1967). The ASTM D25-73, Standard Specifications for Round Timber Piles, classifies round timber piles according to the manner in which their load-carrying capacity is developed. There are two classes: (1) Friction Piles. Friction piles are used when pile capacity is determined by the friction developed in contact with the surrounding soil, along with the compressive strength of the timber piles used. Table 29 from ASTM Standard D25-73, lists size requirements for friction piles. (2) End-Bearing Piles. End-bearing piles are used when pile capacity is determined primarily by the end-bearing capacity of the soil at the pile tip, along with the compressive strength of the timber piles used. 24 *SUTATIp Jo sasodind 1ofF dt} ww /z7T Jo unUTUTW e oINsUS 02 WW OOF 03 poseertoUT u9eq SABY SONTLA TeNPTATPpUT dy} ‘uM OOH UeYI SSseT Fo dt. dy. Ye sdUeTOzZUND -ITD & 02 92eTNITeD SadUsTAFUMIATI 33nq 9y} 04 pottdde sede, oy. etoyMN :920N 901 90v 90% 90bF 90F LSv. 90v¥ 90% 90% (wu) sosuezZezuMNoITS dt} wnututp (w) yQsue7T OLZI vert 8IIl Tv0T S96 688 84 EZ 95,9) “6S (wu) 323nq wWorzZ WU PTE odUeTEFUMIITD UNUTUTW portnboy “(WLSV) e9UerTezuMdITS dt wNUTUTW YIM SodUdTAaFUNDITS 33nq petFtoeds - sattd uoTITIy “67 STqeL 242 Table 30 from ASTM Standard D25-73 (75), lists size requirements for end bearing piles. Table 30. End-bearing piles - specified tip circumferences with minimum butt circumferences (ASTM). Specified minimum tip circumference (mm) 483 559 635 711 787 889 Minimum circumferences 0.9 meter from butt (mm) PRE Ee PPE BRP RP RP eee PREP Re Pe ail ol 6B We re) a8) .4 4 55) 5) 6 ee b. Wood Sheet Pile. Wood sheet piles are sometimes used for groins, bulkheads and subterranean cutoff walls in a saltwater environment. Wood used as sheet piling is subject to environmental attack and therefore must be treated with preservatives if it is to have a useful life more than a few months. Wood sheet pile should be beveled at the bottom on one side and one edge to facilitate driving and to cause each succeeding pile to wedge firmly against the adjacent pile. Sheet pile should not be driven more than a meter. If deeper penetration is needed, the area along the line of piles should be excavated before driving so that the piles need be driven only a meter to final tip elevation. There are two types of wood sheet pile in general use. Members are sized according to the loads and conditions to be resisted by the sheeting. (1) Tongue and Groove. Tongue and groove sheeting consists of planks milled so that on one edge there is a projecting tongue and on the opposite edge a groove into which the tongue of the adjoining plank is fitted when driven. (2) Wakefield Sheet Piling. Wakefield sheet piling is made up of three layers of planks spiked or bolted together to form a sheet pile, so that the middle plank projects beyond the edges of the planks on each side, thus forming a tongue on one edge and a groove on the other (See Fig. 61). 5. Characteristics of Common Construction Species. Woods normally used in the coastal zone are the domestic softwoods generally available in the United States: Douglas fir, southern pine, 243 WOOD PLANKS Figure 61. Wakefield sheet piling. spruce, hemlock, redwood, cedar, and a number of species of pine, including lodgepole, ponderosa, and white. Hardwoods are less commonly used not because of inferior quality but because of cost or availability. Hard- woods, generally, are more difficult to treat with preservatives. However, special situations may call for hardwoods. For instance, an imported hardwood called greenhart is gaining some acceptance for use as fender piles because it appears to be fairly resistant to marine borers in its untreated state. Tables 31 and 32 list significant characteristics of domestic softwoods and hardwoods, respectively. 6. Destructive Biota. a. General. Although there are many life forms that may eat, live in, or make use of wood in a way that may be called destructive, many are so rare or do so little damage during the useful life of wood structures that they can be ignored relative to the use of wood in the coastal zone. Those that most Table 31. Domestic softwoods. General Douglas Southern characteristics Fir Redwood Pine Shrinkage in volume from green to ovendry (pct) Modulus of rupture 43.7 51.4 41.6 31.4 44.1 MPa (green) (green) (green) (green) (green) Modulus of 7.798 7 539K 5.199 Se 971 7.860 Elasticity (green) | ' (green) (green) (green) (green) GPa 244 Table 32. Domestic and imported hardwoods. No 12.0 to to WH ot 14.5 Shrinkage in volume from green to ovendry (pct) Modulus of rupture 49.5 40.1 41.4 MPa Gea 7568 to 62.5 |to 68.9 (green) (green) | (green) 54.2 20) WW oS (dry) 105.2 (dry) 108.0 (dry) Modulus of 6.047 6.502 7.102 elasticity to 11.63 to 10.16}to 10.20 GPa (green) (green) | (green) 9.108 12.14 9.618 to 14.36 to 12.95|to 12.26 (dry) (dry) (dry) Imported Shrinkage in volume from green to ovendry (pet) Modulus of rupture W254 MPa (green) 206.8 (dry) Modulus of 20.00 elasticity GPa (green) 245 seriously affect the useful life of wood are the shipworms (teredos) of the family Teredinidae and small (2 millimeters) crustaceans of the genus Limnoria. These marine biota are generally more active in clean water with high dissolved oxygen. On land, the most destructive insects are termites. Also on land but more in air, and very destructive in the presence of moisture or intermittent wetting are the fungi and bacteria. Preservative treatment can reduce the destructive effects of the various biota and extend the useful life of wood but cannot completely prevent the attacks. Cracks or holes in the wood or leaching of the preservatives will eventually allow access for some marine borer or nest of termites. b. Teredinidae. These are marine bivalve mollusks that have evolved into a long wormlike shape with its ''shell" parts having become a set of grinders at one end that the teredo uses to bore holes in wood. An adult can be 50 to 100 millimeters long and 5 to 10 millimeters in diameter (Fig. 62). The individual enters the wood as a larva by making a small hole that is never enlarged at the surface. As it grows, the teredo bores a larger hole into the wood at the rate of 20 to 300 millimeters per month to accommodate its whole body and apparently to feed itself (Fig. 63). An infestation of teredos can destroy an untreated pile at the mud line in 5 to 6 months (Kofoid and Miller, 1927). Species found in abundance in U.S. waters are Teredo dtegensts and Teredo navalis. Teredos are sensitive to coal tar creosote treatment. c. Limnoria. These are small marine crustaceans about 2 millimeters long and less than 1 millimeter wide (Fig. 64) that either enter the wood in the adult stage or are hatched and remain in the same piece of wood. They use the wood as habitat and apparently as food supply because they continue to bore holes after they are securely entrenched in the wood (Ray, 1959). They bore at the rate of about 0.5 millimeter per day (Kofoid and Miller, 1927). At this rate, a heavy infestation of limnoria could eat through a 30-centimeter untreated pile in about a year. One species, Limnorta tripunetata, is present off most of the U.S. coastline (see Fig. 65). A subspecies, Trtpunctata mengtes is found all along the Atlantic seaboard and in the Pacific Ocean from the southern end of the South Island of New Zealand to several hundred miles north of Vancouver, Canada. Ltmnorta tripunetata is particularly troublesome because it apparently is not repelled by coal tar creosote preservative (American Society for Testing Materials, 1957). Where L. trtpunctata is present the dual treatment, described in paragraph 6, Preservative Treatment of Wood, is required. Figure 66 shows the damage that can occur from limnoria attack. d. Termites. The principal termite species attacking wooden structures in the United States is a subterranean type named Reticulitermes hesperus. The typical life cycle of this species starts with winged reproductive adults that fly from the nest for the purpose of establishing new colonies. When a pair finds a suitable environment they start a colony. In 5 or 6 years, a colony may contain several thousand individuals (Palermo, 1951). Termites are antlike insects about 5 millimeters long that spend their lives inside an earth nest or gnawing tubes through available wood (except for the winged adults). Termite damage is not evident to casual observation because the outer layer of wood is left untouched for their own protection. The usual evidence of their presence are the piles of fecal pellets that 246 Figure 62. Teredo or shipworm (Rasp, 12)59))< ‘ : agatha, — pares i. 2 é A: © eee se <= - ae eae aes SS eee Figure 63. Typical work of the teredo (Ray, 1959). 247 a Po Figure 64, Live limnoria in their burrows (Ray, 1959). TO ALASKA TO GREENLAND TRIPUNCTATA TRIPUCTATA, PFEFFERI , PLATYCAUDA , ETC... Figure 65. Distribution of limnoria in North America (ASTM, 1957). 248 (oqzoyd toqiey *y'I) ‘“SseTtd uo yOe7ze BTLOUWTT 0} ONp SeTOpuos peoT[ Tel Lopun Faeym poom Fo asdeT{ToD “99 94nsTy te N ‘Sa Eeaaak See f a a 249 are pushed out of the way through small ventholes about 1 millimeter in diameter in the wood. A structure attacked by termites will eventually fail unless the infestation is discovered early and the termites destroyed. Termite control can be accomplished in several ways. Separation of structural wood from the ground and removal of all cellulose material from the ground in the vicinity of the structure are accomplished in the design and construction phases. Dry ground, good ventilation, and exposure to sunlight also discourage termites from nesting. If contact with the ground cannot be avoided as in the case of power poles, pressure treatment with preservatives will discourage termites. Poison can be injected into the wood and nesting areas where termites are established. e. Fungi. The decay fungi, which are of primary concern, consist of microscopic threadlike strands known as hyphae; these aggregate into a mass called mycelium. The mycelium under suitable conditions form fan sheets, especially when developing in a very moist locality. These may give rise to the fruiting body of the fungus which, in the case of the decay fungi, is relatively flat. These fruiting bodies bear enormous numbers of micro- scopic spores which are similar in function to the seeds of higher order plants. The spores are readily distributed by water or air currents, or by men and animals. Spores germinate and penetrate wood by means of hyphae. The fungus may also be spread from decayed material to sound material by the hyphae. In the United States there are many species of fungi that cause wood decay. Two important species are the building poria, Porta tncrassata, and the tear fungus, Merulius lachrymans. The tear fungus is more common in northern United States and Canada; the poria fungus prevails in the south and west (Thomas, 1951). Timber destroying fungi require both moisture and oxygen at a temperature of about 20° to 36° Celsius (68° to 97° Fahrenheit) for optimum growth. Therefore, wood that is kept very dry will not decay nor will wood that is submerged where the oxygen is excluded. Because wood must be kept moist, the term "dry rot" is a misnomer for the crumbly brown rot that results from the action of fungi. Figure 67 shows specimens of wharf timbers heavily damaged by fungi. Control of fungi in wood structures can be accomplished by proper design and by chemical treatment. Design criteria should anticipate meteor- ogical conditions such as fog, rain, or dew which may deposit moisture on wood surfaces. Wood structures should be designed to provide for drainage of wood surfaces and eliminate joints and pockets where moisture can collect. Where exposure to moisture is severe and cannot be eliminated by design, pressure treatment with a wood preservative is required. Coal tar creosote, copper napthenate, pentachlorophenol and salt preservatives such as chromated zinc chloride are used separately or in combination for fungi control. 7. Preservative Treatment of Wood. a. General. To extend the life of wood for both economical and practical use in the coastal zone, it must be protected from its natural enemies-- fungi, bacteria, insects, and marine organisms. Effective preservative treatments have been found to discourage the natural enemies and extend the useful life of wood to about four to five times that of untreated wood. 250 *(queuqaedeq roqzey sotesuy soy Jo Asaqzanod ojoyd) (snsunz) jor Arp Aq posewep sioqut} Fareym FO suoutoods “£9 eINSTYy 251 Untreated wood can be used effectively for temporary structures and facili- Hes b. Pressure Processes. The most effective method of treating wood with preservatives is by means of pressure. There are a number of pressure processes that employ the same general principle but differ in the details of application. Treatment includes loading the timber on tramcars, which are run into a large steel cylinder, bolting the cylinder door, and pressure applying the preservative until the required absorption has been obtained. Two principal types of pressure treatment, the full-cell and empty-cell, are in common use (U.S. Department of Agriculture, 1952). (1) Full-Cell Processes. In pressure treatments with the so-called "full-cell" or Bethell process, a preliminary vacuum is first applied to remove as much air as practicable from the wood cells. The preservative is then admitted into the treating cylinder without admitting air. After the cylinder is filled with preservative, pressure is applied until the required absorption is obtained. A final vacuum is commonly applied immediately after the cylinder has been emptied of preservative to free the timber (or charge) of dripping preservative. When the timber is given a preliminary steaming-and-vacuum treatment, the preservative is admitted at the end of the vacuum period following steaming. It 1s impossible to remove all the air from the wood cells regardless of the method of treatment employed. For this reason, even under the most favorable conditions, there is some unfilled airspace in the cell cavities of the treated wood after impregnation by the full-cell process. (2) Empty-Cell Processes. Two empty-cell treatments, the Lowry and the Rueping, are commonly used, both of which depend on compressed air in the wood to force part of the absorbed preservative out of the cell cavities after preservative pressure has been released. In the Lowry process, which is also designated as the "empty-cell process without initial air," the preservative is admitted to the treating cylinder at atmospheric pressure. When the cylinder is filled, pressure is applied and the preservative is forced into the wood against the air originally in the cell cavities. After the required absorption has been obtained, pressure is released, a vacuum is drawn, and the air under pressure in the wood forces out part of the pre- servative absorbed during the pressure period. This makes it possible, with a limited net retention, to inject a greater amount of preservative into the wood and to obtain deeper penetration than when the same net retention is obtained with the full-cell process. The Lowry process is convenient to use in any pressure-treating plant, since no additional equipment is required. The Rueping process is called "empty-cell process with initial air"; this process differs from the Lowry empty-cell process in that air is forced into the treating cylinder before the preservative is admitted. The air pressure is then maintained while the cylinder is filled with preservative; thus, the wood cells are left more or less impregnated with air pressure. c. Classification of Wood Preservatives. Wood preservatives may be grouped into two broad classes; preservative oils and waterborne preserva- tives. Each of these classes may be further subdivided in various ways. For example, preservative oils include petroleum refining byproduct oils 252 such as coal-tar creosote and other creosotes, mixtures of coal tar creosote with coal tar, petroleum, or other oils, solutions of toxic chemicals such as pentachlorophenol or copper naphthenate in selected petroleum oils or other solvents, and various mixtures of these solutions with the byproduct oils and mixtures. The waterborne preservatives include solutions of single chemicals such as chromated zinc chloride (CZC) or chromated copper arsenate (CCA), which are not resistant to leaching, and various formulations of two or more chemicals that react after impregnation and drying to form compounds with limited solubility and sometimes with high resistance to leaching. Preservatives vary greatly in effectiveness and in suitability for different purposes and use conditions. The effectiveness of any preserva- tive depends not only on the materials of which it is composed, but also on the quantity injected into the wood, the depth of penetration, and the conditions to which the treated material is exposed in service. (1) Coal-Tar Creosote. Coal-tar creosote is defined by the American Wood Preservers Association as a preservative oil obtained by the distilla- tion "of coal tar produced by high-temperature carbonization of bituminous coal; it consists principally of liquid and solid aromatic hydrocarbons and contains appreciable quantities of tar acids and tar bases; it is heavier than water; and it has a continuous boiling range of at least 125° Celsius, beginning at about 200° Celsius." Coal-tar creosote is highly effective and is the most important and most extensively used wood preservative for general purposes. Coal-tar creosote solutions vary and usually contain from 30 to 70 percent of coal tar by volume; the most prevalent mix contains 50 percent coal tar. (2) Chemicals Dissolved In Solvents Other Than Water. Preservatives composed of toxic chemicals carried in nonaqueous solvents, such as petroleum- oil distillates, are now being used to an increasing extent. These were originally devised for the purpose of providing a clean treatment without causing swelling of the wood and were originally applied by nonpressure methods. A shortage of cresote that developed during World War II created an active interest in the use of these preservatives as a possible substitute for creosote, especially in the pressure treatment of poles. Particular attention was directed to the chlorinated phenols, which are known to have a high degree of toxicity. Pentachlorophenol is the best known and most widely used in this groun., Other preservatives of this type, which in the past have been largely limited to use in surface treatments, are the metallic naphthenates, such as copper naphthenate. The latter has also been used to a limited extent for pressure-treated poles. Although some of these toxic chemicals, particularly pentachlorophenol, have given excellent results over a considerable period of time, service records are still inadequate to evaluate them completely in comparison with coal-tar creosotes. (3) Waterborne Preservatives. A variety of chemicals in water solution are used as wood preservatives. These include zinc chloride, sodium fluoride, arsenic in various forms, copper sulfate, and similar toxic chemicals. Most of these salts are used in combination with one or more 253 other chemicals, frequently including a chromium compound. Chromated zinc chloride (CZC), which is composed of a mixture of zinc chloride and sodium dichromate, has come into wide use in recent years. The preservative is now much more extensively used than straight zinc chloride, which was formerly the most widely used waterborne salt. A less widely used compound, Fluoro-chrome-arsenate-phenol (FCAP), is one of the preservatives listed in the current standards and government specifications. Arsenic compounds have been used as preservatives for many years. They are important ingredients of a number of proprietary preservatives, some of which have demonstrated high effectiveness and are extensively used. Three effective compounds commonly used are chromated copper arsenate (CCA), acid copper chromate (ACC), and ammoniacal copper arsenate (ACA). Three types of CCA are specified in Interim Federal Specification (U.S. Department of Agri- culture, 1974). The type is chosen according to availability and economics. Copper sulfate, although extensively used in Europe for many years and demonstrated to be moderately effective in retarding decay, has found little use for wood preservation in the United States except in certain proprietary preservatives, in which it is combined with other chemicals. Several of these preservatives are of high effectiveness and extensively used. Copper sulfate is corrosive to iron and steel and, therefore, cannot be used alone in ordinary treating equipment. (4) Proprietary Preservatives. Various patented or proprietary pre- servatives are sold under trade names for pressure treatment. For the most part they are composed of various waterborne salts and are injected in water solutions. Others employ a volatile solvent to carry the toxic substance into the wood. Some of the waterborne preservatives contain chemicals that are intended to react after injection into the wood and to form substances that are of low solubility and resistant to leaching. Wolman salts is one of several proprietary names for a waterborne salt, chromated copper arsenate (CCA), also known as "green-salt.'"' Chemonite is another proprietary name for ammoniacal copper arsenate (ACA). Other proprietary names for preservatives can be found in the American Wood Preservers Association Standard (AWPA) M9. It lists a number of proprietary names for each of the standard preservatives. 8. Specific Applications for Treated Wood. a. General. Tables 33 and 34 indicate the amount of preservative to be retained in various wood forms using approved practices for preservative treatment with creosote and solutions containing creosote, pentachlorophenol, and waterborne preservatives. The net retentions in the tables are minimum penetration requirements. Higher net retentions may be needed for severe use conditions and should be specified when applicable. Data in the tables are taken from Federal Specification TT-W-571J. Coal-tar creosote, creosote-coal tar solution, creosote-petroleum solu- tion, and pentachlorophenol in heavy petroleum solvent and the four water- borne preservatives, ACA, and CCA Types A, B, and C are ordinarily ‘to be 254 Table 33. Preservative retention for timber treatment (from AWPA C2 and C18). Retention by SPECIES (pcf) = N a bi = - w nn nN a —_— vo eo a0 wor S om 0 a sen = = Sc Oe 2 & = in Cy | Types of a 8 5 a, 2 @OC ls : = a) c-- el + | Preservative 2O= aa heey ee fe 5 He S-=- 8S OGC fics ae ode He od oo & Fy oro oovowrws~ WH s a DH WY PueevrvuvdTnATD Dw = > oN Hneocooamocrltss = 600 Ome oartenzen no=z = Creosote! 8.0 Pentachlorophenol ACC, ACA, CCA Ground 1 + | Creosote HO o.0 rv Se Pentachiorophenol ae @ | ACC wooed Ke) wv CCA or ACA Creosote! 12.0 Pentachlorophenol CCA or ACA Creosote!? CCA or ACA Saltwater Contact Submerged Creosote! CCA or ACA lIncludes creosote-coal tar. 2Creosote-coal tar not recommended for single treatment of these woods. 3In saltwater atmosphere, above splash zone, use retentions for ''Freshwater and Soil Contact." 4For members under S inches (13 cm) thick. 5In soil contact in saltwater splash zone or atmosphere, use retentions for "Splash Zone." SAWPA C2 lists treatments for these woods "Subject to Marine Borer Exposure," but AWPA C18 does not recommend them for saltwater use. NR: Not recommended. 7Teredo is present with no to light limnoria activity. 8Limnoria activity is moderate to heavy but pholads are absent. 3Limnoria is present with teredo or pholads. ; 255 Table 34. Preservative retention for treatment of wood piles (from AWPA C3). Retention by SPECIES (pcf) Types of Preservative Coastal Douglas Fir Interior Douglas Fir Application Southern Pine Red Pine? Ponderosa Pine“ Jack Pine? Lodgepole Pine Western Larch Creosote! Pentachlorophenol CCA or ACA iss) i= i) AH o ap aoa os ‘A a Far) 3 oO OH Sw 3 ° em Creosote! | 20.0289 CCA or ACA Creosote! CCA or ACA Saltwater (Submerged) 2» 3 ‘Includes creosote-coal tar. *Ponderosa and jack pine piles are not used in saltwater environments. Applies only to red pine piles. C 3Fed. Spec. TT-W-571J does not specify oak and red pine piles for saltwater use. +*Not recommended. “Teredo is present with no to light limnoria activity. SFed. Spec. TT-W-S71J recommends these where teredo is present with light lim- noria activity. Navy prefers these over dual treatment for fender piles. ?Limnoria activity is moderate to heavy but pholads are absent. 8Limnoria is present with teredo or pholads. 256 used for wood exposed to severe weathering conditions, such as contact with soil or water and for important aboveground structures exposed to the weather. Because oil-type preservatives afford protection against weathering and checking as well as against decay, they are generally preferable to waterborne preservatives for the treatment of sawed wood that is to be used in contact with the ground. If cleanliness, freedom from odor, or paintability is essential, either of the four waterborne preservatives mentioned above may be expected to give good protection to sawed wood that is selected for its receptiveness to treatment and treated to meet the minimum penetration requirements. The same four preservatives may be used for wood in contact with saltwater where limnoria are the only threat. Pentachlorophenol in a volatile petroleum solvent (Table 33) is ordinarily to be used in above- ground structures, particularly where cleanliness and paintability are re- quired. All the waterborne preservatives (Table 34) are suitable for such use. Pentachlorophenol in a light petroleum solvent is also generally limited to aboveground: use especially where moderate cleanliness is desired and freedom from residual solvent is not essential. If water repellency also is desired in order to avoid surface damage due to wetting during storage, it should be stipulated by the purchaser. In some harbors, condi- tions are highly favorable for limnoria, and the life of creosoted piling may be extended by mechanical barriers. AWPA Standard C3 includes a dual treatment that is recommended for trial in harbors where experience has shown that a high limnoria hazard exists along with other organisms. Painting of treated wood involves special considerations. Wood treated with creosote, solutions containing creosote, and pentachlorophenol in heavy petroleum solvent cannot ordinarily be painted satisfactorily. When re- quested it can be conditioned by the producer to improve its cleanliness. Difficulties may be encountered in painting wood treated with pentachloro- phenol in a light petroleum solvent. Wood treated with waterborne preserva- tives should be properly seasoned after treatment and may require light brushing or sanding in order to provide a paintable product. Since "'cleanli- ness'' is a relative term, it is recommended that the purchaser make known his specific requirements and the end use of the material, and that the supplier be required to furnish evidence that the material be suitable for that use. In the absence of accepted methods for determining cleanliness, paintability, and water repellency of pentachlorophenol-treated wood, the purchaser may elect to use arbitrary test methods which should be described to the supplier. b. Timbers and Lumber. (1) Functioning Environment. The treatment required for marine timbers and lumber depends on the environment in which they function. Timbers subject to the marine environment but not submerged or intermittently submerged, are treated differently than those that are submerged. The reason being that submerged timbers are subject to marine borer attack and must be treated according to the anticipated attack. Unsubmerged timbers are highly subject to fungus attack, particularly where water spray or airborne moisture can frequently wet them, but they cannot be attacked by marine borers. An example of submerged use would be the framing and bracing members of a wood pier. Another would be wales, particularly the lower wales of 257 fender piles and wales at the top of wood groins. These are frequently located at or below the water level. The planks of Wakefield piling used as a groin and wood cribbing below water are other examples. When timber and lumber are used above the water but near enough to be frequently wetted by splash and spray they would be in the spray or splash zone. Pier decks and wood fittings such as handrails are frequently in this use zone. Timber bulkheads and cribbing above water are also frequently in the splash zone. Where wood is used away from the immediate contact with saltwater or its splash and spray, two different treatments are called for. They are pressure treatments that have different retention requirements depending on whether the wood is placed in contact with the soil or above the soil in air. Retention requirements for these uses are shown on Table 33. Examples of wood in contact with soil would be bulkheads and retaining walls using Wakefield piles or horizontal planking supported by vertical piles. Sometimes boardwalks are incorporated into a bulkhead structure and these frequently are in firm contact with the soil. Sand fences and cribs placed above the tide line are usually in direct contact with the soil. Wood in air is probably best visualized in causeway decking (far enough removed from the water to be free of the direct influence of splash and mist) buildings, towers, navigation aids and other such structures built on piles or concrete foundations. Whatever the foundation, wood in air must be clear of the ground by at least 200 millimeters (8 inches) and well venti- lated. In the southern United States or in especially warm and moist climates, additional clearance should be considered (ASCE, 1975). (2) Preservative Retention Standards. The adequacy of preservative treatment may be determined by the quantity of preservative retention or by its penetration into the wood. (a) Retention By Assay. The quantity of preservative required for adequate protection is given by the American Wood Preservers Association (AWPA) in pounds per cubic foot (pcf). The retained quantity is measured by assaying the contents of core samples. Timber and lumber used in submerged locations should be pressure treated using the full cell process to achieve retention equal to or greater than the amounts shown in Table 33. In those parts of the world where teredo and pholad attack is expected and where Limnorta trtpunetata attack is not prevalent, creosote or creosote-coal tar treatment will provide adequate protection. Where L. tripunctata attack is expected, and where either teredo or pholad attack is expected, the dual treatment with creosote or creosote-coal tar and either CCA or ACA preservatives to the retentions shown on Table 34 will give the best protection known (AWPA C3). Timber and lumber in the splash zone can be protected by using either of the oil base preservatives, creosote or creosote-coal tar or one of the waterborne preservatives CCA or ACA to the retentions shown on Table 33. The creosote or creosote-coal tar preservatives are usually preferred because the waterborne preservatives are subject to leaching. 258 Creosote and creosote-coal tar mixtures are commonly employed for sawed material (such as bridge timbers) used under relatively severe conditions. Retentions specified for such timbers vary from about 942 to 3 927 newtons per cubic meter (6 to 25 pounds per cubic foot), about 1 570 to 1 890 newtons (10 to 12 pounds) being most common. Both empty-cell and full-cell methods are employed, depending on the amount of sapwood, retention required, size of timbers, and similar factors. The full-cell process is commonly employed in the treatment of resistant heartwood timbers and timber for use in salt- water. Waterborne salts are widely applied in the treatment of sawed lumber under conditions that make it impractical to employ preservative oils. Specifications for retentions of both preservative oils and water-borne salts often fail to take into consideration the relation of the timber dimensions to penetration and retention. The specifications may require a net retention in large heartwood timbers that cannot be obtained because of the small ratio of surface area to volume, although the same retention might be obtained without difficulty in heartwood timbers of tie size or smaller or in large-size timbers containing a large proportion of sapwood. In timbers containing 50 percent or more sapwood, it is recommended that at least 1 570 newtons per cubic meter of preservative oil be specified. (b) Retention by Penetration. The AWPA standards for adequate penetration of the preservative indicate the required penetration in inches or percent of the thickness of the sapwood, whichever is greater. Penetration requirement of preservatives in timbers and lumber generally varies according to species. However, for some species it also varies by size. Timbers and lumber smaller than 5 inches (127 millimeters) require less penetration when the species is coastal Douglas fir, hemlock or pine species other than south- ern pine and ponderosa. Requirements for penetration are found in tables of AWPA Standard C2. The following are representative examples of preservative penetration requirements found in the tables. For use above ground or in freshwater, the penetration required for southern pine is 63.5 millimeters (2.5 inches) or 85 percent of the sapwood for all sizes. Coastal Douglas fir would require a penetration of 12.7 millimeters (0.5 inch) and 90 percent of the sapwood for sizes 5 inches (127 millimeters) and larger but for sizes under 5 inches the requirements would be 10.16 millimeters (0.4 inch) and 90 percent of the sapwood. Oak, for the same uses, would have only the percent- age requirement with white oak requiring 95 percent of sapwood and red oak requiring 65 percent of annual rings. In the marine environment, the penetra- tion requirements would be similar for each preservative of the dual treatment. (c) Treatment of Cuts and Holes. Insofar as practical, wood pieces should be trimmed, dapped, bored and counterbored before pressure treatment because field treatment cannot match the thorough penetration and distribution of preservatives obtainable in the pressure retort. However, it is not always possible and practical to avoid all field cuts and bores. When pretreated wood is cut in the field it is essential that the exposed wood be generously mopped with the same preservatives. The top faces of field cuts are particularly vulnerable to fungus attack and should be given extra careful field treatment. Wood submerged in saltwater is vulnerable 259 to marine borers that can enter the wood in very small cracks or exposed areas. cee Paliese (1) General. The principal woods used for piling are southern pine and coastal Douglas fir, although a few other woods, such as red pine, lodgepole pine, western larch, and oak, are used in some localities. No untreated wood, commercially available for pilings, either domestic or imported, will resist borer attack for more than several years. However, one species of tropical tree known as greenheart (Ocotea rodtaet or Nectandra rodiaet), which is not treatable, may last 2 or’ 3 years longer than treated Douglas fir, in the same water. Timber piles should conform to the require- ments of ASTM Standard D25. Untreated pine and fir piles usually last no longer than 2 years in the ocean, often less than 1 year where marine borers, such as LZ. trtpunctata, are present in great numbers. Treated piles have a life expectancy averaging 8 to 10 years where trtpunctata are present. Ltmnorta tripunctata was selected as an example because this is the only known species of Limnoria which will attack and destroy heavily creosoted piling (Civil Engineering Laboratory (CEL), 1974)). The Forest Products Laboratory has tested a large number of BERNE NICS to study their effectiveness in protecting wood against marine borers. Results obtained in these experiments, as well as experience in general, have shown that heavy retentions of coal-tar creosote are essential if the best protection is to be obtained (USDA, 1952). The heavy retentions ensure better penetrations and also furnish a reserve supply of creosote to provide against early depletion by leaching. Over much of the coastal region of the United States, marine timbers are exposed to severe borer attack, and it is poor economy to specify retentions that will not give the maximum protection under such conditions. Specifications for such timbers should require treatment to refusal by the full-cell process, and the specified retention should be the minimum that will be accepted. No maximum should be specified. The Civil Engineering Laboratory (CEL, 1974) reports that a compound that is toxic to L. tripunctata does not prevent Teredo diegensts attack and a compound that is toxic to 7. diegensis is not effective against L. tripunctata. Experiments by CEL indicate that a dual treatment of wood piles should be used in moderate or warm waters to effectively defend against marine borer attack. The dual treatment consists of metallic salts, either ammoniacal copper arsenate (ACA) or chromated copper arsenate (CCA) and coal-tar creo- sote. A 157-newton per cubic meter (1.0 pound per cubic foot) treatment of metallic salts is applied in water solution. After drying, the wood is pressure treated with coal-tar creosote to a 3 140-newton per cubic meter (20 pound per cubic foot) retention. The above treatment may be specified as conforming to American Wood Preservers Association Standard C3. This treatment significantly increases the expected life of wood piles used in moderate or warm waters but it also reduces the strength and toughness of the wood. Eaton, Drelicharz and Roe (1978) of the Civil Engineering Labora- tory report that dual-treated piles lose 27 to 54 percent of their untreated flexural strength, measured as modulus of rupture, and about 50 percent of their untreated flexural toughness, measured as energy absorbed per unit 260 volume. They recommend creosote treatment alone rather than dual treatment for fender piles in cases where breakage from impact may limit the useful life before marine borer attack. Appendix B describes their results, in- cluding effects on other mechanical properties. In northern waters or where attack by L. trtpunetata is not anticipated and Teredo is the only threat, pressure treatment of 3 140 newtons per cubic meter of coal-tar creosote would be sufficient. The effects on properties are described in Appendix B. Other chemicals, such as pentachlorophenol, should not be used in seawater because this chemical will hydrolize. That is, the presence of water will split the chemical bonds and unite with the radical ions of the original compound to form acids and bases. Table 34 shows preservative retention requirements as set forth in AWPA Standard C3 for single and dual treatment of wood species most likely to be used for piles in the United States. Preservative retentions in pounds per cubic foot are measured by assay of bore samples. Requirements for adequate preservative treatment of piles include minimum penetrations. Penetration requirements for various species of wood piles and use conditions are also set forth in AWPA Standard C3. Penetration tests are made by gauging the penetration distance from the outside face of the pile. Representative preservative penetration requirements for the wood species most frequently used for piles are presented in Table 35. Table 35. Representative preservative penetration requirements. Foundation or Saltwater Freshwater Dual Treatment Southern Pine 7.6 cm or 90 8.9 cm or 90 SE OI elie pet of the sapwood sapwood Coastal Douglas Fir 1.9 cm and 85 2.5 to 4.4 cm and pet of the SS) SE Oie wine sapwood sapwood. (2) Treatment of Pile Cutoffs, Framing Cuts and Holes. After driving treated wood piles in a wood wharf or another structure, excess wood in the piles is sawed off at the desired elevation. This exposes untreated wood at the cutoff, which necessitates some kind of preservative treatment in place. The usual method is to swab the cutoff with creosote, cover that with Irish flax, and add another coat of creosote before placing the pile cap. On inspection, cones of dry rot have been found in the pile tops with the foregoing treatment, after only a few years' service. A method which has adequately protected the cutoff areas and is inexpen- Sive consists of boring five or six 19.1-millimeter (0.75 inch) holes, about 25.4 millimeters (1 inch) apart in a circular pattern, in the untreated area of the cutoff. This is shown in Figure 68. The holes are then filled with a 50-50 mix of liquid coal tar and creosote. A layer of Irish flax is 26l “(sorTasuy soy JO 340g ey FO AsaqIN0d oO oY) quowzee11 930S00I9 Ie1-[TeoD TOF so{td Fyoynd Butaedoig 89 emnsTy placed on top and covered by a 3.8-millimeter (150 mil) layer of high density polyethylene before placing the pile cap. Side and end grain penetration of the preservative completely impregnates the entire pile top to a depth of more than 25.4 millimeters in less than 2 years. d. Poles. Prior to World War II, most of the pressure-treated poles used in the United States were treated with American Wood Preservers Associa- tion specification grade 1 coal-tar creosote with a specified distillation residue above 355° Celsius of not more than 20 to 25 percent. Coal-tar creosote treatment may still be the preferred preservative under conditions where waterborne preservatives could leach away or cost may be the con- trolling factor. In recent years solutions of pentachlorophenol have attracted attention as substitutes for creosote or for use in mixtures with creosote, and large quantities have been used. Thousands of poles have been treated with pentachlorophenol dissolved in the lighter petroleum oils or with solutions containing various proportions of coal-tar creosote and pentachlorophenol dissolved in a petroleum-oil solvent. These poles have not been in service for sufficient time to determine how the results will compare ultimately with those obtained from creosoted poles. Experimental installations under observation, however, are giving excellent results, so that this preserva- tive may find a wide field of use in the future. Most of the poles that have been pressure-treated and on which the best service records are available are southern yellow pine and coastal Douglas- fir. Preservative retention quantities for these and other species are shown in Table 36. The data are taken from Federal Specification TT-W-571J which gives a more complete specification on the treatment of wood poles. 9. Joining Materials. a. Metal Connections. The various members and parts of wooden coastal structures are in nearly all cases joined together by metal. Most common are the bolts, spikes, and driftpins which fasten heavy timbers in structures such as groins, jetties, bulkheads, and piers (Fig. 69). Another cate- gory includes such items as spike grids and split ring connectors for increasing the shear capacity of bolted joints (Fig. 70), and sheet metal framing anchors for lighter structural framing and miscellaneous hardware such as bearing plates and straps. A third category of metal connection material would include tying items such as rods, wire rope, and chain (Fig. 71). Metal connection material for a timber structure is subject to much the same deteriorating factors in a coastal environment as are metal structures. These are predominantly corrosion and, in some cases, abrasion. They are discussed further in Sections VII and XI. In addition to resisting corrosion, the material may also have to resist chafing, or abrasion by drifting sand, floating debris, or moored vessels. This factor should be considered in selecting the anticorrosion coating or system, as discussed in Section XI. Because even the best protective system will have only limited life in a severe marine exposure, a program of periodic inspection and preventive maintenance will probably be needed. 263 Table 36. Preservative retention for treatment of poles (Fed. Spec. TT-W-571J, AWPA C4 and C23 combined). Retention by Species! (pcf) Preservative Coastal Douglas Western Red Cedar Inland Douglas Fir Western Larch Comal (0) i=} ‘dl A ¢ uu S) AS} r=) 5} (e) ww Ponderosa! Red Pine! Jack Pine Lodgepole Coal-tar : 9 to 123 10.5 to 13.53 12 to 16 Creosote2 Pentachloro- 0.45 to 0.603/0.53 to 0.683 |0.60 to 0.80 phenol in heavy petroleum ACA CCA 1Retentions are for use as utility poles except for Southern, Ponderosa, and Red Pines and Coastal Douglas Fir which are used for building poles as noted in Footnotes 3 and 4. ~According to AWPA C4, creosote coal tar also may be used for utility poles. 3According to AWPA C23, the highest retentions are used for building poles as ten as utility poles. *Fed. Spec. TT-W-571J requires these high retentions for building poles but not utility poles. b. Adhesives. (1) Field Application. At present, the use of adhesives to form or assemble wood structural members is largely confined to factory production of building components. Here the wood parts to be joined can be milled to close tolerances and the joining and curing processes can be closely con- trolled. For use in a coastal structure where they are exposed to the weather or subject to immersion, a wet-use adhesive, phenol or resorcinol resin or a blend of the two, should be specified for shop-fabricated members. Such members have only limited use in coastal structures, primarily for such items as footbridge girders and trusses, and small-craft docks in marinas. There is also some use of adhesives in field assembly of wood structural members primarily for buildings. This use is at present largely in secondary connections where a failure would not be hazardous to life or property. The necessary gluing pressure is often provided by nailing. Because in-field gluing and alinement of material may be much less precise than in the shop, it is necessary to use different adhesives, which, until recently, have not 264 Sh 2S TWO MEMBER JOINT, TWO MEMBER JOINT MEMBERS OF EQUAL MEMBERS OF UNEQUAL THICKNESS THICKNESS MULTIPLE MEMBER JOINT ANGULAR JOINT TIMBER FRAMING DRIFT PIN ORIVEN IN WOOD PILE PINNED JOINT SPIRAL DOWEL Figure 69. Typical bolted and pinned wood joints. 265 APPLICATION SPLIT RING SPIKE GRIDS METAL PLATES & BOLTS CONNECTING WOOD STRINGERS Figure 70. Split rings, spike grids and metal plate connectors. 266 provided the joint strength and rigidity obtainable in factory gluing. The relatively recent development of fast-curing, gap-filling phenolic and phenol-resorcinol resin adhesives for construction may allow onsite gluing to further expand into the area of primary load-bearing connections {American Institute of Timber Con- struction (AITCG); 1974). (2) Shop or Factory Applica- tion. Conditions of service de- termine the type of adhesive required. In general, dry-use (water-resistant) adhesive should be used for interior locations and wet-use (waterproof) adhesive for exterior locations. However, under some conditions, a member glued with dry-use adhesive may be used satisfactorily on an exterior member for certain uses. It is not practical to use both types of adhesives within the length of the same member. If any part of a member's length requires wet-use 3 adhesives, wet-use adhesives must be Figure 71. Pile dolphin tie used throughout its length. It with wire rope. should be kept in mind that the use of a wet-use adhesive will generally increase the cost of a laminated member; therefore, it should not be speci- fied unless actually needed. > : (a) Dry-Use Adhesives. Casein adhesive with a suitable mold inhibitor is the standard dry-use adhesive of the structural glued laminated timber industry. It has proved its dependability for over two generations in Europe and North America. It is used in large quantities by other wood products manufacturers as well as this industry. Casein adhesive with mold inhibitor is satisfactory in properly designed, constructed, and maintained buildings as long as the members are not subjected to repeated wettings or high humidity over a long period of time. Although casein adhesives can withstand some wetting during erection of the members, special attention should be given to the protection of the top face of beams, rafters, or arches during shipment and erection when end or beveled faces are exposed at these locations. Angular cuts are often made that pass through one or more laminations and result in feathered ends on the individual laminations. These surfaces have greater than average moisture absorption and should be properly end-sealed to prevent delamination of the feathered ends. Although such damage is not likely to be of structural concern, it may be unsightly. All end cuts should be well sealed (AITC, 1974). 1 Exterior Use. Two major requirements must be met to ensure proper performance of casein adhesives in exterior locations. If the requirements cannot be met, wet-use adhesives shall be used. Complete 267 protection from the direct effects of precipitation on members must be provided either by undercutting the ends to keep off wind-driven moisture or by the use of fascia boards or end caps to prevent water from collecting on vertical surfaces of the members. Ends of members should be coated with white lead paste or treated with water-repellent sealer before the cap is applied. Casein adhesives are not considered suitable for laminated members intended for exterior use where the moisture content of the wood exceeds 16 percent for repeated or prolonged periods of service. 2 Interior Use. Only one major condition must be satisfied to ensure proper performance of casein adhesives in interior locations: the moisture content of the wood must not exceed 16 percent for repeated or prolonged periods of service. 3 Performance Requirements. Dry-use adhesives shall comply with the requirements of ASTM Standard D3024-72 for structural glued laminated timber. (b) Wet-Use Adhesives. Phenol, resorcinol, and melamine base adhesives will withstand the most severe conditions of exposure. They are more expensive than water-resistant adhesives. Phenol-resorcinol base or resorcinol base adhesives are the most widely used wet-use adhesives in structural glued laminated members. 1 Use. Although the wet-use adhesives may be employed for all conditions of use, they are generally used only when the equilibrium moisture content of the members in service exceeds 16 percent, such as the following: (a) Members which must be pressure treated; (b) marine vessels and structures such as barges, ships, piers, wharves, docks, slips, and dredge spuds; and (c) structures and members exposed to the weather, such as bridges and bridge girders (other than for temporary construction such as falsework and centering). 2 Performance Requirements. Wet-use adhesives shall comply with the requirements of ASTM Standard D2559-72 for structural glued laminated timber. Only adhesives meeting the requirement for wet use shall be used with California redwood. OF Repair Materials and Methods. a. Adhesives. Adhesives are rarely used in field repairs. b. Concrete Encasements. Wood-bearing piles which have received damage from marine borers (Fig. 72) (either partially or totally destroyed) can be restored to their design capacity, in place, by encasing them in a reinforced concrete jacket. Piles are enclosed with nyion jackets (adding steel reinforcement as necessary) and the jacket is filled with a tremie concrete. A similar successful method is to enclose the damaged part of the pile with a fiberglass form, installing the necessary reinforcing and filling the space between the form and the pile with a hydrophyllic epoxy (Fig. 73). 268 *(suwoqysks outTiep dT1yenby Fo Asaqyanosd ojoyd) 4noIr3s pue SULOF SSETSLoqtyZ BSutsn poarteder soettg | = caf ee fe whee: | | y 7) “(S461 ‘pueuno SUTIOOUTSUY SOTJI[TOeY [eAeN °S°f) Wioy sseTsieqtz pue ettd pesewep ~eotdkz Fo yore ys “ZL ernst yj 269. Wood pilings that have been severed by marine borers have been success- fully restored, in-place, by literally dozens of methods. Most of these are based on external reinforcement, such as heavy wall steel pipe, overlapping the upper and lower pile sections, followed by corrosion protection of the steel by a plastic wrap. Small scale tests in the laboratory have proved the efficiency of these methods in repairing piles, both in the bearing and bending capacity, to achieve their full design loads. c. Synthetic Materials Wrap. Wood piles can be protected, in place, from marine borer attack, by wrapping with flexible synthetic sheet such as polyvinyl chloride (PVC) or polyethelene sheeting (cigarette fashion) from 305 millimeters (12 inches) below the mud line to 305 millimeters above the highest tide line. In preparing a wood pile for a jacket it is important that all sharp protrusions be removed. In case of barnacles, sharp edges can be smoothed by various simple hand or mechanical devices (Fig. 74). Modular kits are available which permit fast and positive application from above or below water. This system effectively removes wood piles from their environment. Marine borers attacking the piles while encapsulated under the wraps die from lack of oxygen within 48 hours, while the synthetic sheating prevents further intrusion. This system has been successfully used on both coasts of the United States, Germany, Australia, the Bahamas, and elsewhere for more than 20 years. The U.S. Navy has also used the system on numerous projects (see NAVFAC specification 75M-Bl0a). Other methods of wrapping wood piles with synthetic film before driving have also been tried as shown in Figure 75. Unless the piledriving crew are very careful, the PVC jackets can be ripped during driving. Fortunately, permanent repairs can be made by nailing patches of synthetic film over torn areas with aluminum alloy 5056 roofing nails. d. In Place Treatment of Timber Cracks. If such cracks make the pile structurally unsound and also expose it to internal marine borer action, the crack can be bolted together with form-fitting steel washers on each side of the pile by one or more bolts. The entire area should then be jacketed with a synthetic film jacket. e. Replacement. In wood structures, parts such as framing members are frequently repaired by replacement of the damaged member. Replacement is relatively easy because the fasteners are usually in accessible places and the wood members are in discrete sizes of individual pieces. When repairing treated wood, treatment of the new member must be to the same specification as the original. Cuts and bored holes are to be made prior to pressure treatment in the shop when possible. Cut faces of pieces to remain in place must be coated with similar material as the original. New fasteners should be used where there is any damage or corrosion to the original. Damaged wood piles are removed by pulling, after removing deck and stringers when present. Before pulling, remnants of the damaged pile and 270 ay eS TR SAY a) % .t teem . ter ne eae 6 ~ + carers RO ANY | NS aA, Mire hep ty ! oe ee 271 re’ oe ~~ . ~~ * a \ J Wood-bearing piles with PVC wrapping (photo courtesy of the Port of Los Angeles). Figure 74. (photo courtesy ing 272 PVC wrapped pile ready for driv of the Port of Los Angeles) PaL@unKS 75). | fastenings must be cleared away to make space for the replacement pile. A ’ replacement pile can then be set in the same hole as the original and driven to refusal. If it is to support a deck, the pile is driven alongside the pile cap, cut off below the pile cap, and pulled over into place. The cut is treated with preservatives and shims are inserted to fill the space between the pile and pile cap. A driftpin is then hammered into place to secure the pile. 11. Environmental Considerations. a. Chemical Attacks. Chemical actions of three general types may affect the strength of wood. The first causes swelling and the resultant weakening of wood. This action is almost completely reversible when the swelling solution is removed. The second type of action brings about perma- nent changes in the wood such as hydrolysis of the cellulose by acids or salts. The third action also brings about permanent change in wood and involves delignification of wood and dissolving of hemicellulses by alkalies. (1) Saltwater and Freshwater. Saltwater and freshwater penetrate the wood fibers. Between zero moisture content and the fiber saturation content (about 30 percent moisture content) wood will swell. The rate of swelling is proportional to the moisture content up to the fiber saturation point. As wet wood dries, the outer part of the wood loses moisture faster than the inner parts thus the shrinkage rate is uneven and can result in the development of checks or cracks. When wood is immersed over extended peri- ods, water can soften the fibers. Water and particularly saltwater carries dissolved oxygen and marine biota that can severely impact wood or wood fastenings. As a bearer of oxygen, water enhances corrosion of iron and steel fastenings. When wood is periodically wetted and dried in the presence of oxygen it becomes suscept- ible to fungus which causes dry rot. (2) Strong Acids. Strong acids (such as nitric and hydrochloric) and highly acidic salts (such as zinc chloride) tend to hydrolyze wood and cause serious strength loss if they are present in sufficiently high con- centrations. When the pH of aqueous solutions of weak acids is above 2, the rate of hydrolysis of wood is small and is dependent on the temperature. (3) Wood Oxidation. Wood oxydation by air in dry locations is slow and attacks the spring wood first to produce a rough or weathered looking surface. Very dry wood can resist hundreds of years of normal exposure to oxidation. Wood can be dissolved by strong acids but basically wood is considered to be somewhat resistant to the action of acids and basic hydro- xides. Wood is also resistant to most commercial solvents. b. Pollutant Attacks. Pollution in both the air and water environments may have the effect of prolonging the useful life of wood by reducing the oxygen supply that oxidizes the wood and supports the biota that attack wood. c. Sunlight Exposure Effects. Wood in sunlight will expand because of the increase in temperature. In most structures the wood's increase in length for normal rise in temperature is negligible and as a result secondary 273 stresses due to this change may he neglected. Cut pieces of wood will warp toward the sun unless restrained or dried before use. d. Wave and Current Effects. Because wood has less strength than some other commonly used structural materials, a larger wood member is needed to adequately protect the wood against the force developed by water currents and waves even where a solid face is presented to the wave and current forces. The resilient characteristic of wood, however, allows wood members to absorb impact energy and rebound intact better than concrete and steel. e. Effects of Severe Temperature and Ice. Temperature effect upon wood strength is immediate and its magnitude depends on the moisture content of the wood. If the exposure is above normal atmospheric conditions for a limited period and the temperature is not excessive, wood can be expected to recover essentially all its original strength. Air-dry wood can be exposed to temperatures of about 65.6° Celsius (150° Fahrenheit) for a year or more without significant permanent loss of most of its strength properties. Ice or freezing conditions will impact mechanically by causing fiber failure and thus loss of strength through a reduction of section. f. Marine Organisms. As discussed in subsection 6, Destructive Biota, the principal marine organisms that cause wood destruction in the coastal zone are Teredoes, Limnoria, Poria and Merulius. Most of these animals attack wood as free-swimming organisms. They bore an entrance hole in the wood, attach themselves and grow in size as they bore tunnels into the wood. Wood structures are protected from these animals by proper treating with creosote or coal-tar solutions or by a protective enclosure. g. Periodic Wetting and Drying. Wood in a marine environment should always be protected from excessive moisture or water and therefore has little change in its structural or mechanical properties. If the preserva- tives eventually leach out of the wood cells, then alternate expansion and contraction of the wood cells can result in gradual and slow deterioration. Wood structures have a history of long service life even when subjected to alternate wetting and drying. h. Wind Erosion. Wood being a relatively soft construction material as compared to concrete or metal, it can be eroded by wind action. Wind does not erode wood directly but strong winds picking up particles of sand or other materials will cause a wood surface to wear. Erosion of this kind will usually take place near the ground line. i. Effects of Burrowing Animals. Marine animals will burrow into wood very rapidly unless the wood is protected by appropriate preservatives. Wood is sufficiently soft as to offer little resistance to burrowing attack and in addition serves as a food source to the animals. Onshore termites are very destructive to wood. These attacks, if left unchecked, will result eventually in the loss of all structural properties of wood. j. Effects of Flora. There are no reported effects of flora growth on wood. k. Fire. Wood, when exposed to fire, forms a self-insulating surface layer of char and thus provides a degree of its own fire protection. 274 Although the surface chars, the undamaged wood below the char retains its strength. Heavy timber members will retain their structural integrity throughout long periods of fire exposure because of their size and the slow rate at which charing penetrates inward from the wood surface. 1. Abrasion. In the coastal environment, abrasion of wood occurs from sources such as scour by wind- and water-driven sand as well as the working or rubbing at joints in the wood structure. Abrasion can be from beneficial use as from vehicle traffic on a pier or from rubbing of floats on anchor piles. The wearing away of a wood structure in this manner will eventually reduce the structural integrity of the structure. m. Seismic Effects. Seismic activity can have a significant effect and in some locations a devastating effect. Ground shaking can stress structures to overload and cause destruction. Natural alluvial terraces or manmade landfills in the coastal zone are subject to liquefaction during severe earthquakes which cause the ground to slump and flow horizontally. Structures founded on such terraces in a severe seismic area are subject to destruction if liquefaction occurs. However, under less severe conditions, wood performs very well in seismic events because of its resiliency. This characteristic of wood allows it to flex during ground shaking and reduce the stresses that might destroy structures of more rigid materials. n. Human Activity. Human use of wood structures can eventually cause the wood to wear out; the worn wood parts could be replaced or the whole structure could be abandoned. On wharves and piers ship moorings wear or break fender piles and vehicular traffic on the deck wears out the surface timbers. Human use engenders risks in the form of explosions, fires, and accidental impact loads, all of which can destroy wood members of coastal structures. Vandalism can cause serious damage to wood: some wood may be sacrificed for firewood; wood may be destroyed by the target practice of shooters; and amateur wood carvers may cause deterioration. 12. Uses of Wood In Coastal Construction. a. General. (1) Dimension Lumber. Untreated dimension lumber can be used in temporary situations during the construction phase of a project or where the life of the wood is to be less than a few months. It can also be used in any situations where the wood can be protected either by a covering, for example interior framing of a building, or where it is to be painted and Maintained in a painted state for the projected life of the installation. Untreated dimension lumber should not be used in direct contact with the ground or sea water. Untreated dimension lumber is used in form work for concrete. It is also used in a variety of ways such as for dunnage or machinery supports. Foundations and sill plates for frame buildings are usually pressure treated with chromated copper arsenate. Any use where contact with the earth exposes the lumber to rot, fungus, or insect attack requires treatment to obtain a satisfactory useful life. Specific treatment would be determined by the conditions of service. Exposed uses subject to severe weathering or prolonged (or periodic) immersion in seawater should be pressure treated 275 with coal-tar creosote; otherwise, one of the other treatments could be satisfactory. (2) Piles and Poles. Wood piles and poles used in the coastal environment are nearly all pressure treated with coal-tar creosote to resist insect attack or, in water, marine borers and limnoria. Properly treated piles and poles will also withstand rot and fungus attacks. Piles are used for building foundations, support for piers, wharves, trestles, jetties, groins, and bulkheads. Also, they are used in fender systems plone the wharves and to anchor floating moorings for small boats. It is unlikely that untreated piles or poles would be used in the coastal environment except for temporary uses during construction for false work or to carry electric power and telephone lines to the construction site. (3) Beams and Stringers. Lumber classified as beams and stringers {having 5 inches (125 millimeters) as their least dimension} are seldom used untreated in the coastal environment. The principal use would be in protected space as framing for buildings or covered structures where the covering or painting provides sufficient protection. Coal-tar creosote treated beams and stringers are used extensively in the coastal environment. (4) Glued and Laminated Wood. (a) Plywood. Dry-use plywood is seldom used in the coastal environment because of its extreme susceptibility to the generally high humidity. Any use would have to be very temporary or very well protected from the prevailing moisture. Wet-use plywood has many applications in the coastal environment. Diaphragms in buildings, roofs, walls, and floors are regularly sheathed with wet-use plywood. Plywood is sometimes used for gussets in wood frames to join the members. Plywood is used extensively in making forms for concrete work. Signboards are frequently made of plywood. Covers, such as for pits and valve boxes, can be made of plywood where traffic is light or in nontraffic areas. Wet-use plywood can be further treated with preserva- tives to extend its useful life in extreme environments, such as immersion in seawater. (b) Laminated Wood. Wood in this category is what is generally referred to as "glue-lam," or more properly glued laminated wood. Because of its better quality control, strength, and capability of being sized to suit the need, it can be the preferred material for many applications where columns, posts, beams and girders are used. In the coastal environment, wet-use glue is absolutely essential and glue-lam members must have pre- servative treatment in any use where other wood forms would require it. (5) Miscellaneous Wood Forms. Although most people think of finished lumber and timbers cut to rectangular sizes from large trees or of piles peeled and trimmed when they think of wood, there are other useful forms of wood that can be used in the coastal zone. Small branches, saplings, 276 brush, cane, bamboo, and reeds have all been used to make devices to control water currents, stabilize bottom sediments or to control dry sand buildup. Where these wood forms are indigenous to the area or readily available they can be valuable materials. b. Offshore Structures. (1) Breakwaters and Caissons. Wood is seldom used in offshore structures of this type but dimension lumber and wet use plywood may be used for navigation aids or other incidental small structures that may be mounted on offshore breakwaters and caissons. (2) Pile Dolphins. Wood is frequently used offshore for pile dolphins and other mooring or anchorage devices such as guide piles for floats or piles for channel markers. Pile dolphins are clusters of wood piles tied together as in Figure 71. (3) Floats. Wood is used extensively in the construction of floating structures. Although the tendency is toward synthetic materials for small flotation devices, wood remains the most used material for framing flotation units and providing a platform for access and mooring fastenings. Wood flotation units such as logs could be used to form floats or booms for the containment of surface debris. c. Shore-Connected Structures. (1) Breakwaters and Jetties. Wood uses in shore-connected break- waters and jetties would be the same as described for offshore structures. (2) Groins. Wood is frequently used in the construction of groins. Wakefield sheet piles are commonly seen used as shown in Figure 61. The sheet piles are secured with timber wales at the top. Wood planks spanning between wood piles create another type of groin structure as seen in Figure 76. (3) Bulkheads. Wood bulkheads are usually one of two kinds. Wakefield sheet piles are driven along the bulkhead line and tied back to the embankment by timber wales and tie rods to imbedded anchors (deadmen). Otherwise, vertical piles acting as soldier beams are driven at regular intervals along the bulkhead line and wood planks are placed to span hori- zontally between them. Piles can be tied back to deadmen. (4) Revetments. (a) Pile Revetment. Slopes can be stabilized using parallel piles laid along the slope as shown in Figure 77. Piles used this way must be securely tied to headers or staked down. (b) Fascine Mattresses. The word ''fascine'' comes from the Latin "fascina'' meaning a bundle of sticks. Fascine mattresses are used as submerged scour aprons and as filter blankets along revetments. There are many ways to construct the blankets but they basically all consist of sticks tied together in bundles and arranged in mattresses about 20 meters (62 feet) wide and up to 200 meters (620 feet) long. The mattresses are Aut Figure 76. Beach protection with "billboard" groins, Ninilchik Harbor, Alaska. Figure 77. Piles laid on slope to prevent beach erosion, Ninilchik Harbor, Alaska. 278 made in a place that is normally dry but can be flooded (either at high tide or by removing a gate) for towing the mattress to its final location. The mattress is then loaded with stones and sunk into place. It is then covered with stones as needed to resist the expected currents. Examples of fascine mattresses are shown in Figure 78. Finer material is placed on the bottom of the mattress where it contacts the sand and coarser material is on top to support the stones. These mattresses will deteriorate rapidly if left where they would receive periodic wetting. Therefore, they will only work where they are completely submerged all the time. Where damage by marine borers is expected, preservative treatment could be applied but the cost of treatment may indicate that some other material be used (Van Bendegon and Zanen, 1960). (5) Submerged Screens. Submerged screens for current control can be made of "wattles" (flexible branches woven around posts) as shown in Figure 79 or can be made by combining stones and small poles (or bamboo) into cribs. The cribs are formed by forming a lattice work of poles to form a cage (crib) and filling it with stones for stability. Figure 80 shows some crib types. (6) Piers and Wharves. Piers and wharves may be made entirely of wood construction with incidental use of metal fastenings and rock for slope protection. Piles, pile caps, stringers and decking would all be treated and placed as discussed in earlier paragraphs of this section. These wood members can also be used in conjunction with other materials, such as con- crete piles. Mooring dolphins and fender piles for piers and wharves are frequently made of wood to take advantage of the energy absorbing property of wood even when the remainder of the structure is of some other material such as concrete. (7) Sand Fences. Fences made of brush have proved more effective than fences made of boards in building sand dunes on the Outer Banks of North Carolina (Savage, 1963). In this installation, brush was held upright between pairs of wood plank rails as shown in Figure 81. The filtering action of the brush apparently trapped more sand than the wind deflection action of wood slats. 279 at 7) wine llauyute iy Ut escine Matlreas: i val | Mi i i o net 1 meager i a = in ah ay I vt 8’ i $f 8 SS wy) = NS a | BS St sgussasausesetasee) | pais Cross- Section ASAE) CIGCCUd Figure 78. Two methods of making fascine mattresses (Van Bendegon and Zanen, 1960). Figure 79. Submerged current control screen made of "wattles" (NEDECO, 1959). 280 FRUSTRUM CRIB TRIANGULAR PRISM CRIB Figure 80. Examples of wood-formed cribs (Van Bendegon and Zanen, 1960). Figure 81. Sand fence using brush for filter material (Savage, 1963). 281 LX AS TGS 1. General. a. Chemical and Manufacturing Properties. Chemically the term "plastics" is applied to a large group of synthetic materials that are processed by molding or forming into a final shape. Plastics are composed of chainlike molecules of high molecular weight, called polymers, that have usually been built up from simpler monomers. All plastics share many common properties and, in general, have four things in common. First, at some stage in their production they are soft and pliable and can be formed, by the application of heat, pressure or both, into definite desired shapes. Second, plastics are organic materials; i.e., they are based on a carbon structure. This distinguishes them from such materials as metals, ceramics, and concrete. Third, plastics are synthetic materials and are products of chemical processes that alter the characteristics of the raw materials from which they derive. Fourth, plastics are high polymers; they consist of monomer atoms joined together into molecular aggregations. Different monomers are used to manufacture each different type or family of plastics. Each plastic has a particular combination of properties, pro- cessing requirements, and economics that make it ideally suited for certain applications, yet unsuitable for many others. b. Thermoplastics and Thermosets. Plastics in general may be classified into distinct groups. These are thermoplastics and thermosetting plastics or thermosets. Thermoplastics soften repeatedly when heated and harden when cooled. At high temperatures they may melt and at low temperatures become brittle. The process of heating and softening and cooling and hardening may be repeated indefinitely for plastics such as polyethylene, polyvinyl chloride, acrylics, nylon or polystyrene. Thermosetting plastics go through a soft plastic stage only once. When hardened, an irreversible change takes place and they cannot be softened again by reheating. Some thermosetting plastics are polyesters, epoxies, phenol-formaldehydes, melamine-formaldehydes and silicones. c. Copolymers and Composites. Plastics can be combined like metal alloys to attain the best qualities for a particular end use by selectively drawing from the best attributes of the blended components of the polymers. The process is referred to as copolymerization and the products are called copolymers. Plastics used for structures, including those used in the coastal zone, are most commonly composites or copolymers rather than pure forms. Reinforced plastics are one category of composites in which the plastic is strengthened and stiffened by combining it with high strength fibers such as glass. Sandwich-type plastics contain a variety of strong, thin facings and lightweight cores. There are also the polymer concretes, which contain plastic matrix in place of or in addition to inorganic cement. d. Structural Properties from Additives. Because all plastics are synthetic, during their production various things can be done to alter their characteristics by the introduction of additives. These include 282 plasticizers, fillers, colorants, stabilizers, and impact modifiers. Plastics which are hard and rigid or brittle at normal temperatures can be made pliable and flexible by the addition of plasticizers. Fillers are normally added to both thermoplastics and thermosets to enhance their processing, performance, or economics. For example phenolics, without the addition of fillers, are hard and brittle, shrink in molds and may crack. The addition of finely ground wood flour makes it easier to mold and less costly. Powdered mica will enhance electrical resistance while the addition of asbestos will improve heat resistance. Impact resistance can be improved by the addition of chopped fibers such as natural fibers, tire cord, rayon or glass. Colorants are easily added to plastics although they are not usually necessary in coastal structures. Stabilizers are an important group of additive materials used to increase the resistance of plastics to deteriorating influences of weather, ultraviolet light, or radiation. Most plastics in their pure form do not have a great deal of resistance to these environments. The addition of stabilizers retards thermodegradation and oxidation. Materials with these kinds of additives, in outdoor exposures, may have a design life of 30 to 40 years. Another important category of additives are the impact modifiers. The inclusion of various fillers or plasticizers will increase the impact resistance of plastics which are normally very brittle. e. Durability Properties. In addition to structural qualities, plastics possess other desireable characteristics as a construction material. They are easily formed, corrosion resistant, lightweight, wear resistant, energy absorbent, impact resistant, flexible and ductile, and are used for insulation due to their thermal and electrical resistance. Energy absorb- tion and impact resistance vary with the different plastics. Rubber, being a synthetic and not usually considered a plastic, can be formulated to have a high degree of impact resistance within a large range of stiffness characteristics. Fire is a necessary consideration in the selection of all structural materials. Plastics will burn or disintegrate if exposed to fire or high temperatures. Some will burn easily, some slowly, others with great difficulty. Some will not support combustion in the absence of flame. Improved fire resistance can be achieved by incorporating flame-retardant chemicals into the molecular structure of the plastic materials. Phosphorus and halogens have been effectively used for this purpose. 2. Geotextile Filters. a. General. Because the most common use of plastics or geotextiles in coastal construction is as a filter, that use is the predominant topic of this section. These filters have been known as filter fabrics, construction fabrics, plastic filter cloth, geotechnical fabrics, and engineering fabrics. ASTM Joint Subcommittee D-18.19/D-13.61 is developing test procedures for evaluating these fabrics and has adopted the name of "geotextiles."' Geo- textiles are used in engineering as filters, materials separators, and reinforcement for soils. These fabrics may be used in coastal structures to 283 perform one or more of these roles, however; they are most frequently used as filters which permit the passage of water through the fabric but not soil or sand particles. Geotextiles used as materials separators prevent the mixing of materials that should remain apart such as poor subgrade soil and good subgrade gravel. Geotextiles have also been successfully used as reinforcing in the paving of roads and to restrain lateral movements of embankments built on soft soils. Koerner and Welsh (1980) give design guidance for many uses. The use of geotextiles has expanded rapidly in the past 20 years and many different kinds are available today. However, there are constraints that must be removed before geotextiles achieve unqualified acceptance. One of these is lack of standardization. Many fabrics are made by suppliers in different ways, out of different materials, and for different uses. In choosing a fabric for a project, it may be necessary to consider tensile, elongation, and puncture properties, plus factors such as fabric elasticity, porosity, permeability, and resistance to abrasion, chemicals, light, weather, and temperature as well as resistance to biological attack. Because geotextiles have many different uses in coastal structures, drainage ditches, riverbank protection, and subgrade construction, no one fabric is right for all applications. It remains to be determined just what properties are important for each end use and what range of values for each property is sufficient. However, based on the successful use of many geotextile filters over the past 20 years, the promise of longevity is exceedingly favorable. A prospective geotextile user should obtain advice and information from engineers experienced in their use as well as from more than one supplier. The term geotextile filter as used in this report refers to a permeable fabric constructed of synthetic fibers designed to prevent piping (prevent soil from passing through it) and remain permeable to water without signifi- cant head loss or without permitting the development of excessive hydrostatic pressure. b. Design Properties. A geotextile filter must be sufficiently permeable to relieve the hydrostatic pressure differential between its sides by allowing the passage of ground waterflow without detrimental head loss, and it must prevent the passage, or piping, of adjacent granular or fine soil. A geotextile is used to replace all or part of a conventional filter system consisting of one or more layers of granular material. Figure 82 illustrates a geotextile replacing a layer of gravel beneath a revetment, showing how the filter is designed to prevent protected soil from being washed through the overlying armor. It also demonstrates how a geotextile can be incorporated into a toe protection apron. To be effective, the geotextile must be designed to suit the grain size, ground water, and wave conditions of each specific site as well as the type of structure in which it is to be included. In order to function satisfactorily, the geotextile filter must have the physical durability and filtering integrity to perform consistently throughout the design life of the structure. Durability depends on the chemical composition of the fibers, construction of the fabric, and physical properties of the fabric in its completed (finished) form. To ensure durability, specifications for fabric should describe the basic chemical 284 GEOTEXTILE WITH WITH EQUIVALENT GRAVEL FILTER GEOTEXTILE FILTER GEOTEXTILE METHOD OF INCORPORATING ‘GEOTEXTILE INTO TOE SCOUR PROTECTION APRON Figure 82. Geotextile filters in revetments. 285 composition, fabric construction, and additives. The 1977 Chief of Engineers Civil Works Construction Guide Specification CW 02215 (U.S. Army Corps of Engineers 1977) states that 'The plastic yarn shall consist of a long-chain synthetic polymer composed of at least 85 percent by weight of propylene, ethylene, ester, amide or vinylidene chloride." All geotextiles for coastal applications must meet this requirement. Filtering integrity depends on the fabric's ability to resist piping through the fabric and clogging. These properties are discussed in subparagraph c below. These topics are covered in subparagraphs 2c(1) and 2c(2). Filtering integrity also depends on the fabric's resistance to loss of permeability due to distortion of the pores by elongation of the fibers under stress, a physical property of the fabric, or by melting in fire. | (1) Chemical Stability and Resistance. The first extensive research and testing of geotextiles for filters was by Calhoun during the period 1969 to 1972 (Calhoun, 1972). In the course of his investigations, tests were conducted to determine the chemical stability and resistance of three types of synthetic polymers, polyvinylidene chloride, polypropylene and polyethylene. Further research by Bell and Hicks (1980) also investi- gated chemical properties of these three polymers plus polyester and polyamide. The results of these testing programs established the fact that these synthetics have high chemical stability and resistance to chemical attack (acids and alkalies), and can be used in conventional soil applica- tions with confidence. If the fabric is to be used in an environment containing petroleum products, it is recommended that the geotextile's resistance to these materials also be determined. (2) Fabric Construction. Selection of a geotextile for a filter should be based on the filtering and physical properties as well as the chemical properties of the fabric consistent with the site-specific require- ments. Bell and Hicks (1980) found that most fabric engineering properties are more strongly influenced by the fabric construction than the polymer. One of the most extensive and thorough fabric strength testing studies, involving 27 commercially available fabrics, was performed for the Army Engineer District, Mobile, by Haliburton, Anglin, and Lawmaster (1978). It was concluded that fabric construction had more influence than the type of synthetic fiber in the fabric. Because fabric construction is the pre- dominant factor affecting physical properties and filtering performance, three general types of fabric construction are discussed: woven, nonwoven and combination fabrics. (a) Woven Fabrics. As the term implies, woven fabrics {commonly called cloths) are manufactured by weaving. Normally, the yarns cross at right angles, overlapped one over the other. The longer direction of the cloth, when it is being woven, is called the warp or machine direc- tion. The narrower direction is referred to as the fill or cross-machine direction. In geotextiles, normally the warp direction is stronger than the fill, although the cloth may be produced with equal strength in both directions or a stronger fill than warp. Filters are woven using a variety of yarns discussed below. 1 Monofilament Yarns. Monofilament yarns are a single filament of a polymer, which prohibits absorption of water by the yarn. This was the only type of geotextile used in coastal structures in the United States from 1958 to the mid 1970's. Fabrics woven of monofilament 286 i yarns have relatively regular and uniform pore sizes. "Some engineers believe that because of their simple pore structure, the monofilament fabrics are more reliable filter materials and use them in critical installation, where their higher cost can be justified" (Bell and Hicks, 1980). The fabric is thin. 2 Multifilament Cloths. Multifilament cloths are woven of yarns containing many fine filaments, except fibrillated yarns which are produced from synthetic sheets. Fibrillated yarns are formed of fibers from sheet plastic film. All multifilament fabric can be produced with higher tensile strengths than monofilaments. With the exception of fib- rillated fabrics, multifilament cloths also have a simple, relatively regular and uniform pore size, and generally are thin. Fibrillated fabrics have a slightly more irregular pore system and generally are thicker. 3 Mono-Multifilament Combination Fabrics. Mono-multi- filament combination fabrics contain monofilament yarn in one direction and multifilament in the other. The pore sizes are consistent and controlled by the weaving process. The openings are oblique to the plane of the fabric. The cloth is slightly thicker than monofilaments. 4 Slit-Film. The term as used herein refers to a fiber which has a width many times its thickness. Such fabrics are also called ribbon, split-film, slit-tape, and split-tape. Because of the poor dis- tribution and uneven sizes of the pores, there is a great variation in their retention and filtration capabilities. The fabrics are thin. Slit- film fabrics are not recommended for use as filters. (b) Nonwoven Fabrics. Nonwoven fabrics include all materials which are not woven or knitted. They consist of discrete fibers, which may have a preferred orientation or may be placed in a random manner and do not form a regular or simple pattern as do wovens. Nonwoven fabrics are composed of either continuous filament or staple filament fibers. Con- tinuous filaments are extruded, drawn and laid in the fabric as one con- tinuous fiber. Staple filaments are cut to length before being laid in the fabric. The engineering properties of nonwoven fabrics are controlled by the fiber type, the geometric relationships of the fibers, and the methods of bonding. Four methods of bonding are described below. 1 Needle Punched. Barbed needles are punched through the fabric web, perpendicular to the plane of the fabric and withdrawn, - drawing filaments with them. This causes the fabric to become mechanically entangled. These fabrics have a very complex pore structure and the fabrics are compressible, so the nature of the pore structure changes. This results in a different in-situ filtration performance than might be indicated by isolated permeability and particle retention tests. The fabric is relatively thick and has the appearance of felt. 2 Heat Bonded. The fabric is subjected to a high temperature, which results in the filaments welding themselves together at the contact points. These fabrics have a relatively discrete and simple, though irregular, pore structure and are thin. 3 Resin Bonded. The fabric web is impregnated with a resin which caats and cements the fibers together. Pore structure and 287 fabric thickness are intermediate between the two fabrics described above. Normally, they have less permeability and fewer voids. 4 Combination Bonded. A number of nonwoven fabrics are a combination of two or more of the above methods to construct a finished product. Due to the variety and numerous combinations available, it is impossible to make an applicable statement regarding pore properties and thickness of this classification of fabrics. (c) Combination Fabrics. Fabrics have been produced by combin- ing woven and nonwoven fabrics using one or more of the bonding methods described above. Usually, these combination fabrics are produced to enhance a particular property or performance requirement not found sufficient in either of the singular types of fabric construction. Hundreds of such com- binations are possible with an equal, or greater, number of finished fabric forms and properties. Each must be evaluated in view of the application being considered. The 1977 CE Guide Specification CW 02215 (U.S. Army, Corps of Engineers, 1977) states that "The fabric should be fixed so that yarns will retain their relative position with respect to each other. The edges of the fabric should be finished to prevent the outer yarn from pulling away from the fabric." Regardless of the fabric construction, this requirement is necessary to ensure continuous acceptable performance. (3) Physical Property Requirements. In few other applications is a filter exposed to so many damaging forces as in most types of coastal struc- tures. Consequently, physical property requirements for geotextile filters are more stringent for these applications. Suitable physical (mechanical) properties are not only necessary during the construction process, but in the permanent structure as well. Due to such structure's constant exposure to dynamic loading, from waves and currents, armor and underlayer movement, earth and hydrostatic pressure, and rapid fluctuations, any geotextile used must have sufficient tensile and abrasive strength to retain its integrity throughout the life of the project. The test methods used to determine geotextile's physical property re- quirements are primarily textile tests. However, the test methods and re- quirements referred to herein can be related to the field performance of woven geotextile filters. Evaluation has confirmed successful performance of fabrics having a particular character. Many of the required test results have been verified by more than 20 years of field performance. If test methods or results and specifications other than those re- quired in this section are employed, they should be thoroughly evaluated to determine if the method and results are applicable to the intended function or performance in the application of interest. Test methods for required physical property determination are described in Appendix C. (a) Properties Required for All Applications. 1 Tensile Strength. Adequate fabric strength is necessary to withstand dynamic forces, prevent the movement of the geotextile filter through voids in the stone layer above the fabric, as often occurs with 288 aggregate filters (Dunham and Barrett, 1976), and permit the use of larger stones adjacent to the filter, thereby possibly reducing the overall thick- ness of the structure (Barrett, 1966; Dunham and Barrett 1976). When armor is removed or rearranged, the fabric's independent strength should also retain the soil (Barrett, 1966; Fairley, et al.,1970) and prevent cavity formation. 2 Elongation at Failure. This is part of the tensile test described in Appendix C. Percent of elongation must be known because exces- Sive elongation will distort and enlarge the pores and change the soil retention capabilities (piping resistance) (Steward, Williamson, and Mahoney, 1977). If excessive elongation is necessary to develop the fabric's ultimate strength, the fabric will probably never develop its required strength in- situ. 3 Seam Strength. It is advantageous to use geotextile filter sheets or panels in large lengths and widths in most applications. The larger panels reduce the number of overlaps required which is the most probable cause for error during construction. Fabrics are manufactured in various widths 1.8 to 5.2 meters (6 to 17 feet), and then sewn together or bonded by cementing or by heat to form large panels as much as 25.6 meters (84 feet) wide. When sections are sewn together the yarn used must conform to the chemical requirements in subparagraphs 2b and 4b. If the seam strengths are too low the sheets may separate and permit piping to develop. 4 Puncture Resistance. Puncture resistance is required to enable the geotextile filter to survive placement of other materials on it during the construction process and to prevent rupture or penetration by the overlying material when the structure is exposed to wave action. 5 Burst Strength. Burst strength must be considered to assure the engineer that the fabric will retain its integrity when subjected to earth forces especially when the material above it contains relatively large voids. 6 Abrasion Resistance. In all types of use, abrasion resistance is important during construction. In one case, fabric was damaged during construction of a French drain merely by placing small filter aggregate into the trench it lined. In coastal structures such as revetments, abrasion resistance is required not only during construction but also throughout the life of the structure, for these structures are subjected to continuous or intermittent wave attacks which result in movement of the overlying material adjacent to the fabric. (b) Optional Requirements for Special Site Conditions. In certain climatic conditions and geographic locations, it may be desirable to test the geotextile for freeze-thaw resistance, high temperature surviv- ability, and low temperature survivability. When soils in the project site are contaminated, or are subject to infiltration, by high quantities of acids, alkalies, or JP-4 fuel, it may be advisable to test the geotextile's resistance to the specific contaminant. Test methods are described in Appendix C. (c) Properties Required for Construction Conditions. The physical properties of geotextiles required for specific sites and structures 289 vary with loadings as well as with function. Loadings may be classified in three service categories: (1) Severe dynamic loadings, (2) dynamic and static loadings, and (3) most stringent placement and drainage. Severe dynamic loading is characterized by continued abrasive movement of materials adjacent to the fabric due to wave action. Dynamic and static loadings are characterized by more restrictive placement procedures to limit abrasive movement and include gabion applications. The most stringent placement controls and drainage applications nearly eliminate abrasive movement of materials adjacent to the fabric. This category includes weepholes, linings of vertical walls, relief wells, linings for French and trench drains, and wrap collector pipe. For each loading category certain construction parameters and limitations must be met. In Tables 37 and 38 construction limitations for each category are listed with reference to three specific applications: quarrystone revetment, block revetment, and subaqueous applications. Block revetment includes pre- cast cellular block (a cast or machine-produced concrete precast block having continuous voids through the vertical plane normally with smooth or near vertical sides) and interlocking concrete block (a cast or machine produced concrete block having interengaging or overlapping edges). The subaqueous applications include groins, jetties, and breakwaters; scour protection for piers, piles, and caissons; and toe aprons for bulkheads. Minimum geotextile filter physical, property requirements are shown in Table 39 based on the construction limitations in Tables 37 and 38. Test methods are described in Appendix C. The physical property requirements in Table 39 are not the same as stated in the current Civil Works Construction, Guide Specification, Plastic Filter Fabric, No. CW-02215 (U.S. Army, Corps of Engineers, 1977). Because this report is concerned only with coastal struc- tures, the test methods and requirements set forth herein are based on field performance and verification in these types of structures and relevant laboratory research. c. Filtering Integrity. (1) Piping Resistance Criteria. To prevent piping, it is necessary to know the soil retention capability of the geotextile filter or granular filter when considering a filter system. In his extensive and thorough research and development project with geotextiles for filters, Calhoun (1972) developed a special procedure for determining the piping resistance (soil retention capacity) of fabrics. The result of this procedure, described in Appendix C, was to determine the equivalent opening size (EOS) of the fabric. Knowing that the soil retention ability of a fabric is directly related to the hydraulic pressures, flows and forces it encounters, Calhoun (1972) conducted hydraulic filtration and clogging studies to develop a formula that related the EOS to required performance criteria. For geotextile 290 Table 37. Construction limitations: quarrystone revetment.! CATEGORY A B C Parameter Severe Dynamic Stringent Dynamic and Static Placement and Loading Loading Drainage Steepest Slope 1V on 2H 1V on 2.5H 1V on 3H Min. Gravel thickness above filter None None 20 cm Stone adjacent to geotextile: Max. stone weight? Max. drop height Max. stone weight . 1.3 KN Riprap weight range 5 : 0.22 - 2.2 kN Max. drop height 5 0.61 m Max. stone weight 1.3 - 8.9 KN Max. drop height placed Subsequent Stone Layer: Max. stone weight Max. drop height Max. stone weight Max. drop height Max. stone weight | Max. drop height Max. stone weight Max. drop height NOTE: a. Stronger principal direction (SPD) and seams of the geotextile . should be perpendicular to the shoreline. b. There is no limit to the number of underlayers between the armor and the geatextile. lThis table may also be used for sand core breakwaters (a jetty, groin or breakwater in which the core material consists of sand rather than stone). 2Not applicable 3Weight of quarrystone armor units of nearly uniform size. 4Weight limits of riprap, quarrystone well graded within wide size limits. t 291 Table 38. Construction limitations: block revetments and subaqueous applications. CATEGORY Block Revetment! Precast Cellular Block? Steepest Slope: Individual Blocks 1V on 3H Cabled Blocks" : 1V on 2H Max. block weight : 3.1 kPa Interlocking Concrete Block? Steepest slope 1V on 2H Min. gravel thickness Above filter 15.2 cm Max. block weight >3.1 kPa Subaqueous Applications® SI ee Steepest Slope 1V on 15H 1V on 15H 1V on 15H Stone Adjacent to Geotextile: Max. stone weight 8.9 KN Min. drop through water 1.5m Max. stone weight >13.3 KN Max. drop height placed Subsequent Stone Layer(s) Max. stone weight Max. drop height IStronger principal direction (SPD) and seams of the Brot Te should be perpendicular to the shoreline, 2with flat base. 3Not applicable. ~Precast cellular blocks cabled together in a horizontal plane. No limit to the number of underlayers between the armor and the geotextile. 6As in normal construction practice: the geotextile does not require special limitations in these layers. 292 Table 39. Minimum Property Tensile Strength*-spp! BPD2 ~ WPDS Elongation at Failure Seam Strength* Puncture Resistance Burst Strength Abrasion Resistance't- High Temperature Survivability Test method A Severe Dynamic Loading 1.56 kN 0.98 kN <36% 0.87 KN 0.53 kN 3450 kPa 0.44 kN 0.29 KN B Dynamic §& Static Loadings 0.89 kN 36% 0.80 KN 0.53 kN 0.29 KN geotextile filter physical property requirements. CATEGORY C Stringent Placement & Drainage 0.89 kN 0.44 kN 36% 0.36 kN 0.29 kN 1650 kPa 0.27 KN 0.15 KN 90% of required strength 80% of required strength Low Temperature Survivability , 85% of required strength 90% | Effects of Acids of required strength Effects of Alkalies 90% of required strength Effects of JP-4 Fuel 85% of required strength IspD = Stronger Principal Direction 2BPD = Both Principal Directions 3WPD = Weaker Principal Direction “In accordance with the specifications for the tests for these proper- ties, these forces are applied over a width of 25.4 millimeters (1 inch). 293 filters adjacent to coarse-grained soils containing 50 percent or less particles by weight passing U.S. No. 200 sieve, the piping resistance is calculated using: Pgs of protected soil > 1 EOS where Dgs5 is the effective grain size'in millimeters for which 85 percent of the sample by weight has smaller grains. For geotextile filters adjacent to fine-grained soils containing more than 50 percent particles by weight passing U.S. No. 200 sieve, the EOS should be no larger than a U.S. No. 70 sieve. Fabric with the largest possible EOS should be specified to promote drainage and reduce the likelihood of clogging. Geotextiles with an EOS smaller than the U.S. No. 100 sieve should not be used as filters. When the protected soil contains particles ranging from a 2.54-centimeter (1 inch) size to those passing the U.S. No. 200 sieve, only the gradation of soil passing a U.S. No. 4.sieve should be used in selecting the fabric. Whenever the protected soil is so sized or graded that a fabric cannot satisfy the above requirements and the soil is to be protected with a multi- layered granular filter, a geotextile filter will often satisfy the require- ments of all but the filter layer immediately adjacent to the protected soil (primary filter layer). There are additional restrictions regarding the percent of open area (POA) of the geotextile which must be considered in applying the piping resistance formula. The POA determination method is described in Appendix c. These criteria for determining piping resistance have been widely and successfully used by the engineering profession. The original EOS determination method developed by Calhoun (1972) was based on the sieving of rounded to subrounded sands. Geotextiles rated by this method were used in the filtration and clogging tests which resulted in the piping criteria formula stated above. The 1977 CE Civil Works Construction Guide Specification CW-02215 (U.S. Army, Corps of Engineers, 1977) modified the original EOS determination method by substituting glass beads for sand. The 1977 Guide Specification EOS determination method is described in Appendix C. Many geotechnical engineers and soil testing laboratories who had experience with the sand determination method prior to 1977 indicate the sand behavior is more typical of the material to be protected. Most often stated objections to beads are: (a) they develop static electricity; (b) there is a size problem: many are not "true" when received from the manufacturer; (c) a continuous breakdown of the beads occurs during sieving; (d) different results are obtained for the same geotextile when beads are used compared to the results when sand is employed: generally beads yield a larger apparent opening value (smaller sieve number) than sand (i.e., beads - EOS equals No. 50 sieve vs. 294 sand - EOS equals No. 70 sieve), on some occasions the discrepancy is reversed. (B.R. Christopher, P.E., Corporate Laboratory Director, STS Consultants Ltd. (formerly Soil Testing Services, Inc.), Northbrook, Illinois, personal communication, 1979-82). Other sources have stated similar experiences and indicate inconsistent results are obtained when sand is replaced by beads. Geotextile filter selection criteria for piping resistance are the same for all applications in coastal structures. The criteria are based on the work of Calhoun (1972); the U.S. Forest Service criteria; experience with laboratory testing, field experiments, installations and monitoring as presented by Steward, Williamson and Mahoney (1977); and the authors' (of this section) personal experience, performance records, and communication with users and researchers. Geotextile filters meeting the Calhoun EOS determination criteria have had field verification (service records) for more than 20 years. (2) Clogging Criteria. In shore protection structures (such as revetments), geotextile filters may be exposed to severe static and dynamic loading, turbulent flows, rapid fluctuations, high-pressure differentials, and sudden or regular drawdowns. Designers primarily concerned with sub- surface drainage must recognize the necessity for more stringent property and performance criteria for fabrics being considered for this environment. It is especially true with respect to the filtration and clogging performance, because, if the filter clogs, it could cause a more severe problem than if it had been omitted. Usually underdrains have low rates of flow and relatively low hydraulic gradients, Due to the large-grained sand present in many coastal areas, filters adjacent to French and trench drains and surrounding collector pipes are often exposed to higher flow rates than would normally be expected in these applications. It is the responsibility of the designer to specizy a geotextile filter that retains the soil being protected, yet will have openings large enough to permit drainage and ‘prevent clogging. Many fabric suppliers provide fabric permeability and waterflow rate at a specified head as fabric performance criteria; however, these data are of little use in establishing filter-clogging criteria. (a) Corps of Engineers Criteria. Calhoun (1972) developed the most widely used filtration-clogging geotextile filter criteria in 1972 after an extensive 3-year research effort. While the criteria were rather simple, they were based on numerous hydraulic-soil-fabric filtration and clogging tests. Using his method described in Appendix C, Calhoun de- termined the EOS of the fabric and in addition determined the POA. As mentioned in the discussion of piping resistance, with certain restrictions for fine-grained soils, Calhoun's criteria allowed the ratio of the soil's Dgs to the fabric's EOS to be equal to or greater than 1. The criteria also had an added limitation that no woven fabric should have a POA less than 4 percent nor EOS with openings smaller than U.S. No. 100 Standard Sieve. Calhoun established that the larger the POA, the less the fabric was susceptible to clogging. 295 The current 1977 CE Guide Specification (U.S. Army, Corps of Engineers, 1977) introduced the gradient ratio (GR) based on Calhoun's original work. Determination of gradient ratio is set forth in Appendix C. (b) Forest Service Criteria. The U.S. Department of Agriculture Forest Service (USDAFS) has conducted numerous laboratory and field tests, including an evaluation of geotextile filter performance in various types of structures. Their criteria for piping resistance (soil retention) and clogging are similar to Calhoun's, as discussed above and stated in Appendix C, the EOS-POA combined criteria. The service does have some disagreement with the current 1977 CE Guide Specification (U,S. Army, Corps of Engineers, 1977) as discussed by Steward, Williamson, and Mohney (1977). They feel that the currently recommended GR test should be modified to represent the range of varying seepage rates and fabric strains accompanying the enlargement of openings in nonwoven fabrics due to stretching anticipated in the field, and that intermittent flow should be added. They suggest that the GR test has not been confirmed by monitoring field performance. Concern is also ex- pressed that due to higher elongation, EOS of nonwoven fabrics will be more variable and more subject to change under load than that of woven fabrics. For all critical and severe filter applications the U.S. Forest Service indicates that only woven geotexttles should be used (Steward, Williamson, and Mohney, 1977). The USDAFS definitions of these terms are quoted below: "Critical: Projects where failure of the filter could result in failure of an expensive or environmentally sensitive part of a project, such as: (1) rock blankets greater than or equal to a 3-foot-horizontal thickness, (2) retaining structures, (3) road fills greater than 10 feet in height, (4) underdrain trenches greater than 5 feet in depth, and (S) bridge repair. Severe: Conditions of moderate to high seepage out of erodible soils with a hydraulic gradient evident moving from soil toward the filter, such as: (1) spring areas, (2) soils with flowing ground water, and (3) soils with high internal hydrostatic pressure." Both the above definitions seem applicable to most coastal applications. Calhoun (1972) also concluded that only woven fabrics be used in coastal projects. The Forest Service indicates a preference for the woven filters and that the sometimes "lower material cost of the lightweight non-woven fabrics for critical or severe seepage conditions appear to be outweighed by 296 peor the risk and consequence of possible failure at this time". They also state that in similar installations, graded aggregate filters have a 50 percent chance of functioning properly, while woven geotextile filters have a rate near 100 percent. (c) Combined Criteria. In order to develop a laboratory and field performance verified geotextile selection criteria for filtration- clogging properties, the authors of this section relied on the experience of knowledgeable users, their own personal experience, and a combination of parts of reports citing criteria relevant to coastal applications by Calhoun (1972), Steward, Williamson, and Mohney (1977), and CE 1977 Guide Specifi- cation (U.S. Army, Corps of Engineers, 1977). To achieve desired clogging resistance, woven geotextile filters adjacent to soils containing 50 percent or less particles by weight passing through a U.S. No. 200 sieve, should have an effective POA equal to or greater than 4.0 percent. (When overlayed with stone, the POA of the geotextile is the effec- tive percent open area. If half of the geotextile is covered by flat based concrete blocks without a gravel layer between the fabric and the blocks, a POA equal to or greater than 8.0 percent is required to yield an effective POA equal to or greater than 4.0 percent.) Nonwoven geotextiles in the same application should have a gradient ratio equal to or less than 3.0. This same gradient ratio is used as the criteria for selection of all geotextiles adjacent to soils with more than 50 percent particles by weight passing the U.S. No. 200 sieve, or soils with a very slight gradation curve or those that are skip-graded (gap-graded). Geotex- tiles with the largest possible POA available in the required EOS sieve number should be specified. As stated previously, ASTM Subcommittee D-18.19/D-13.61 is developing test methods for geotextiles. When these, or other, test determination methods and formulas are submitted to the specifier, they should be evaluated to determine if their results meet the requirements discussed above. It is recommended that both sets of tests be conducted and the results correlated to the requirements stated in this report. _d. Placement. The geotextile filter must be laid loosely, not ina stretched condition but free of wrinkles, creases, and folds for all applications on slopes and beneath jetties. When the slope continues above and beyond the structure, the filter should be keyed-in by being placed in a trench at the upper terminus of the structure. When a gravel layer is placed on the geotextile, it must have sufficient permeability so that it does not reduce the flow from the filter. The largest size sheets available should be used to reduce the number of overlaps required. Overlaps of adjoining sheets should be a minimum of 46 centimeters (18 inches) and staggered for installations in the dry. For underwater applications, the overlaps should be 1 meter (3 feet). Strict inspection and enforcement is required with respect to drop height limitations and overlaps. On slopes, construction begins at the toe and then proceeds up the slope. Horizontal underwater placement (such as groins, ‘jetties, and scour 297 protection for vertical walls and piers) starts at the shoreward end and proceeds away from the shore, or starts adjacent to the protected structure and proceeds to the outer limits of the scour protection. When securing pins are required to prevent the geotextile from slipping during construction, they shall be 3/16-inch in diameter, of steel, pointed at one end and fabricated with a head to retain a steel washer having an outside diameter of no less than 3.8 centimeters (1.5 inches). The pins should have a minimum length of 46 centimeters when used in soils having a medium to high density. For loose soils, longer pins should be used. They should be inserted through both strips of overlapped fabric at the midpoint of the overlap. The maximum pin spacing along overlaps should be 0.6 meter (2 feet) for slopes steeper than 1V on 3H, 1 meter (3 feet) for slopes of 1V on 3H to 1V on 4H, and 1.5 meters (5 feet) for slopes flatter than 1V on 4H. Additional pins shall be installed as necessary to prevent any slippage of the geotextile, regardless of location. e. Repair Method. If the geotextile filter is damaged during the placement of the fabric or of the stone (or blocks) on the fabric, it should be repaired as follows: Cut the damaged part of the fabric out of the sheet and position an undamaged piece of geotextile filter, 1.2 meter (4 foot) longer in each direction, where the fabric has been removed. Extend the edges of the new fabric 0.6 meter (2 feet) beyond and under the edges of the undamaged original filter. f. History of Uses in Coastal Construction. The first use of geotex- tiles was as a filter beneath an interlocking concrete block revetment on the Atlantic coast in South Palm Beach, Florida, in 1958 (Dallaire, 1977). The fabric used was woven of monofilament yarns of polyvinylidene chloride (saran), containing stabilizers to make the filaments resistant to ultra- violet and heat deterioration. The equivalent opening size (EOS) was equal to a U.S. Standard Sieve No. 100 and the percent of open area (POA) was 4.6 percent. Physical properties were as follows: tensile strength approxi- mately 890 newtons (200 pounds) (warp), 445 newtons (100 pounds) (fi11); elongation at failure less than 33 percent; burst, 1 790 kilopascals (260 pounds per square inch); puncture, 310 newtons (70 pounds); abraded strength, 250 newtons (57 pounds) (warp), 85 newtons (19 pounds) (fill). In the following 4 years, geotextile filters were used in a number of ~- coastal structures on the east coast of the United States. In every in- stance, the fabric was the same as in the first use at South Palm Beach. While the fabric performed satisfactorily in these installation, field observations during construction led to the conclusion that construction would be simplified, and a superior structure would result, if a filter could be developed with higher tensile strength, burst, puncture and abrasion resistance for use in conjunction with quarry stone construction materials. Development of a geotextile woven of polypropylene monofilament yarns consisting of at least 85 percent propylene and containing stabilizers and inhibitors to make the filament resistant to ultraviolet and heat deterioration was completed in 1963. The new fabric had an EOS equal to a No. 70 U.S. Standard Sieve and a POA of 5.2 percent. Physical properties were as follows: tensile strength approximately 1 690 newtons (380 pounds) (warp), 979 newtons (220 pounds) (fill); elongation at failure less than 30 298 percent; burst, 3 720 kilopascals (540 pounds per square inch); puncture, 620 newtons (140 pounds); abraded strength, 440 newtons (100 pounds) (warp), 310 newtons (70 pounds) (fill). In 1969 the U.S. Army Engineer District, Memphis inspected three bridge abutments protected by geotextile filters overlayed with 560-newton (125 pound) stone. In one abutment built in 1962, the fabric, similar to the 890-newton tensile strength fabric referred to above, had numerous holes attributed to abrasion and could be easily torn by hand. The other two abutments, built in 1964 using the stronger, 1 690-newton tensile strength fabric, were in excellent condition and no evidence of loss of strength was apparent (Fairley, et al!., 1970). The following list identifies the first uses of geotextile filters in coastal structures by U.S. government departments and agencies: 1961 - U.S. Navy, U.S. Naval Station, Mayport, Florida. Beneath stone revetment. 1962 - U.S. Army Corps of Engineers, Coastal Engineering Research Center, Fort Belvoir, Virginia. Beneath interlocking concrete block revetment (Hall and Jachowski, 1964). 1962 - U.S. Department of the Interior, National Park Service, Colonial National Historical Park, Yorktown, Virginia. Beneath stone revetment and repair of damaged shoreline riprap. 1963 - U.S. Department of Agriculture, Forest Service, Lake Winnibigoshish, Unippewa National Forest, Minnesota, Erosion Control beneath gabions (first filter application with gabions). 1964 - U.S. Air Force, Capehard Marina, Tyndall Air Force Base, Florida. Beneath stone breakwaters. ; By 1966 woven geotextile filters had been included in the following types of coastal structures in North America: filters beneath stone and inter- locking concrete block revetments, linings for the interior of vertical seawalls (bulkheads) to permit the relief of water through weepholes and the joints (tongue and groove, king pile and panel, T-pile and panel), wrapping for collector pipes and ''french drains," beneath stone jetties, groins and breakwaters, security for the slopes of "sand core" jetties, linings for the interior of steel cells, and scour protection around steel cells and piers of drilling platforms down to a 46-meter (150 foot) depth as in the North Sea (Barrett, 1966). Lake Texarkana, Texas, was the location of the first installation of a nonwoven textile in a coastal structure in the United States. Construction in 1976 consisted of a precast cellular block revetment lying directly on the fabric. The geotextile filter was composed of 100 percent polyester con- tinuous fiber, the filaments mechanically interlocked by needle punching. The EOS equaled a No. 100 U.S. Standard Sieve, other properties were: tensile strength, 1 330 newtons (300 pounds); elongation, 65 percent; burst, 3 450 kilopascals (500 pounds per square inch); abraded strength, 730 newtons (165 pounds). 299 3. Other Forms of Plastics Used in Coastal Structures. a. Flexible Forms for Concrete. High strength fabric such as nylon may be used in conjunction with concrete to control erosion. To form slabs, the fabric is put down as a double layer along a bank or shoreline and acts as a mold form for concrete that is injected into it. Figure 83 shows two types of double layer fabric forms. Figure 84 shows installation of a concrete filled form. FILTER POINTS FABRIC COVERS CONCRETE FILLE aH FILLER Figure 83. Two types of double layer fabric forms (courtesy of Fabriform). Grout-filled fabric tubes may be arranged in various configurations along the shoreline. They are useful as groins, dikes, breakwaters or weirs. Figure 85 shows an arrangement of tubes and a filling point. Figure 86 shows the use of fabric pillows as concrete forms for erosion control. Koerner and Welsh (1980) give examples of slab and tube forms. b. Sheet Forms. Synthetic sheet materials made of polyethylene, vinyl or rubber are used as linings and as covers for controlling water seepage and preventing pollution. These liner-type materials may be bonded together to form a large continuous sheet. As such it is useful in lining storage ponds or pits where coastal pollution is a problem. Synthetic sheet materials are also utilized in harbors to control and to clean up oil spills. Flexible plastic sheeting is held between floats so that it passes through the surface layer as a pollution dike (Fig. 87). The polluting material is retained within the flexible floating dike. Such diked areas can be set up in advance of operations that might result in a spill. For example, the regular off- loading of oil at a cargo terminal would require that a containment boom be on standby or deployed in a particularly environmentally sensitive location. The confined retained pollutant can then be cleaned up by a simple surface skimming operation. c. Molded Forms. (1) Guards and Rubbing Strips. Fenders or guards are frequently fabricated from rubber and high strength synthetic plastics or plastic- fabric combinations. Examples of these structures are illustrated in Figure 88. 300 -(wxogtaqey Jo Asez4N0d ojoyd) paT[eisUt Bureq susoZ STAGES IOART OT co” “” Brey AP “ Pmt . 5 b, i ” “Wt ( ‘ va i *y wh qnod "yg oansty 301 Sie ‘ S 3 oN 2 wa s Figure 85. Longard tubes being filled with sand for beach nourishment project, North Sea Coast Germany (photo courtesy of Langeoog). Figure 86. Concrete-filled bags of synthetic fiber used for shore protection (photo courtesy of Fabricast). 302 HANDLE FLEXIBLE CLOSED - CELL FOAM FLOTATION KEVLAR FILAMENT STRENGTH MEMBER STEEL BATTENS (INTERNAL) BALLAST WEIGHT OlL CONTAINMENT BOOM URETHANE COATED SYNTHETIC FABRIC LEAD Figure 87. Oil containment boom made of synthetics. 303 PES TT a a ess kt e docks and piers ° timber jetties tanker terminal Spee ® port and harbor walls structures Figure 88. Typical uses of molded high density polyethylene (courtesy of Schlegel Corporation) . (2) Fenders and Bumpers. Rubber and high density polyethylene (HDPE) are excellent and widely used materials for fenders and bumpers. High density polyethylene has excellent properties for marine application such as sliding fenders. It has excellent low friction properties, good toughness, and resistance to abrasion and impact damage. High density polyethylene may be cross linked to form a three-dimensional structure to make it even higher in strength. However, its elongation and flexibility properties are reduced as its strength is increased. Polyethylene outlasts wood rubbing strips on fenders four to five times, is easily machinable or extrudable, and requires little maintenance. It also has greater fire resistance than wood. This fire resistance can also be © enhanced by certain formulation modifications of the polyethylene. Rubber, in the form of tires and molded shapes, is utilized with excellent success as rubbing bumpers. Old tires are frequently found in harbors as bumpers for small craft. The energy absorption capacity of old tires is unpredictable and not relied upon for larger vessels. For larger vessels, a chain net of tires over a rubber or HDPE cushion block to provide energy absorption may be used. Figure 89 shows such an application. ad, Praja Rorams. (1) Fiber Reinforced Plastic (FRP). This special pipe is coming into wide usage today. It is often referred to as. RTRP (reinforced thermosetting resin pipe). As mentioned above, thermosetting resins such as 304 —_- ——— Figure 89. Sea cushion with tire chain net (photo courtesy of Seaward International). epoxy or polyester may be used in combination with fiberglass to manufacture a tough corrosion-resistant pipe. This pipe is utilized in and around the waterfront to avoid the necessity of corrosion procedures such as coating, coating and wrapping,or cathodic protection. The material costs of FRP pipe are higher than steel pipe. However, installation costs for FRP pipe can be significantly lower than that of steel pipe due to its lightweight, ease of handling, and capability of making field joints. In fact, the total installed cost of FRP piping is usually lower than that for steel pipe in the same size range. (2) Nonreinforced Pipe. Nonreinforced plastic pipe in the smaller size range, to about 25-centimeter (10 inch) diameter, is used in Many construction projects. It does not have the structural strength of FRP in large diameters but is sufficiently strong in most small diameter applica- tions. Nonreinforced plastic pipe is produced by the extrusion process. The present technology for pipe extrusion uses PVC powder compounds produced by cold blending techniques that do not require high-cost intensive mixing equipment. Nonreinforced plastic pipe has a large use in the electrical industry as electrical conduit and, because of its lower cost and excellent corrosion resistance, is finding expanded use as a water and drainage pipe. 305 e. Epoxy Grouts. Epoxy resins, when mixed with sand, form a chemical grout which has excellent chemical and physical properties. These grouts may be used to patch cement construction such as roadways, or to patch certain worn or corroded metal parts. These epoxy grouts have superior adhesion properties with high strength and corrosion resistance. Many other grout types are available, e.g., silicates, acrylics, and lignin. 4. Environmental Considerations. a. General. The environment interacts and combines with the magnitude and duration of stress, strain, and temperature to further alter material response and strength of plastics. Chemical environments, {for example, ultraviolet (UV) exposure, contact with petroleum products and sustained elevated temperature}, can have profound influence on performance and hence must be a consideration in the design and use of plastics. However, many synthetics have a high chemical stability and resistance to chemical attack by acids and alkalies. The failure to design for environmental effects as they interact with sustained stress or strain has been the chief cause of failure of plastic products. Fillers and plasticizers alter the basic response and strength of plastic materials. Fillers (e.g., clay, limestone, carbon black, and other inert materials), introduced to increase stiffness, improve processing characteristics, or lower costs, may also be used to improve UV resistance or heat resistance. Plasticizers change the physical properties of plastics such as impact resistance, flexibility and toughness and abrasion resistance. The introduction of strong fibers, such as glass, will improve strength, stiffness, and dimensional stability. Stabilizers are an important group of additive materials, used to increase the resistance of plastics to the deteriorating influence of weather, UV light, or radiation. Stabilizers are also used to retard degradation by heat. Flame-retardant chemicals, such as phosphorous and halogens, can be incorporated in the molecular structure to improve fire resistance. Plastics in common use in the coastal environment, such as the epoxies, polyesters, polyethylene, polypropylene and polyvinyl chloride, are generally not considered to be biodegradable. However, these plastics in virtually all structural forms (such as tanks, pipes, bouys or geotextile fabrics) have a high corrosion deterioration in the coastal environment and when exposed to chemicals, except for some of the aliphatic solvents, such as keytones. b. Geotechnical Fabrics. Atmospheric temperature, chemicals (in concentrations normally found in soils), and wetting and drying are factors having little or no effect on geotextiles conforming to the chemical and physical requirements stated in the text and Table 39. Trees may grow through the fabric. In the few cases where this has been observed, there was no detrimental effect to the function of the filter because the geo- textile was sealed tightly against the tree trunk at the point of penetra- tion. No standard test method has been developed to determine the biological resistance of geotextiles. However, all investigators have concluded that fabrics composed of the synthetic polymers described earlier, are inert to 306 biological attack, with the possible exception of polyamide (nylon). Research has shown, however, that bacterial activity in the fabric inter- stices can clog a fabric, reducing its permeability. B.C. Beville, U.S. Department of Agriculture, Soil Conservation Service, Orlando, Florida, in 1968 performed the following test (Calhoun, 1972). Two slotted collector pipes were installed in separate trenches. Each was wrapped with a geo- textile filter of different physical type and chemical composition. Ina matter of weeks, the nonwoven glass fiber fabric on one pipe became clogged with an iron sludge. The sludge was formed by iron bacteria that oxidized and precipitated iron into the water. There was no sludge buildup on the woven polyvinylidene chloride cloth on the other pipe. Other factors discussed in detail below can also have an adverse effect on the performance or physical properties of geotextiles. (1) Ultraviolet (UV) Radiation. All synthetics discussed pre- viously, without UV stabilizers, are subject to degradation when exposed to UV radiation. The fabric will be exposed to UV rays during construction. The length of time of exposure will vary with the size of the project and the construction sequence. In a drainage installation, when completed, there is no concern for the effects of UV radiation. However, for certain types of coastal structures, such as revetments, UV resistance must be considered. Continuous or intermitent UV exposure may result from any one or a combination of the following: (a) The stone armoring may be relatively thin and rays penetrate to the fabric through voids in the armor; (b) the armor may be precast cellular block, cast with a hole through the concrete from the top to the bottom of the block, per- mitting daily exposure to UV rays; (c) armoring materials may be rearranged or removed by storm or other occurrence exposing the previously shielded fabric; and (d) a construction oversight may have permitted the geo- textile filter to be exposed after the structure's completion. The 1977 CE Guide Specification (U.S. Army, Corps of Engineers, 1977) requires that the fabric "contain stabilizers and/or inhibitors added to the base plastic if necessary to make the filaments resistant to deteriora- tion due to ultraviolet and/or heat exposure." For most coastal installa- tions the phrase "if necessary" should be eliminated. Of the synthetics discussed, in an untreated state (no stabilizers or inhibibitors added to the polymer) polyester has the greatest resistance and polypropylene and polyethylene the least resistance to UV degradation. Steward, Williamson, and Mohney (1977) report that untreated nonwoven polypropylene and polyester fabric samples completely disintegrated within 18 months when left exposed in the field. Bell and Hicks (1980) indicate that, when constructed of the same fiber and having an equal amount of UV stabilizers, woven monofilament fabrics would be the most resistant to UV radiation, multifilament woven and the nonwoven fabrics would have inter- mediate resistance, and slit-film woven would be the least resistant. 307 One monofilament woven polypropylene fabric in which carbon black was incorporated in the filament during the extrusion process retained satis- factory strength properties after 11 years of exposure (no cover material) in a coastal environment (Soil Testing Services, 1980). As yet, no standard test has been developed to measure the length of time fabric, either untreated or treated, may be exposed to UV before harmful degradation takes place. ASTM Subcommittee D-18.19/D-13.61 is currently attempting to develop such a test method. As stated above, there are numerous design reasons for UV stabilizers being necessary in geotextiles for coastal structures, especially in the absence of a method for determining fabric life: (2) Fire. The melting point varies with the polymer used in the fabrics from 135° to 260° Celsius (274° to 500° Fahrenheit). If fire gener- ates heat beyond the fabric melting point, it will alter the geotextile filter's piping and permeability performance. Some polymers will burn (support combustion), while others only melt. (3) Ice. Ice formation within the structure of thick nonwoven fabrics will enlarge the pore openings. Depending on the polymer and fabric construction, some recovery (of unknown extent) may take place. The soil retention capability will be reduced. (4) Kinetic Energy, Kinetic energy, in the form of direct wave attack on unarmored geotextiles may cause rupture. Wave energy transmitted by armor stone may damage covered geotextiles, if requirements described in Tables 37 and 38 are not met. (5) Abrasion. Abrasion can tear fibers, weakening the fabric as mentioned earlier. Fabric can be abraded by overlying material during con- struction and storms, and by waterborne debris if the cover is removed. (6) Vandalism. If the fabric is not protected by a cover of earth or armor it can be damaged by vandalism. 308 X. RECYCLED AND OTHER MATERIALS 1. Introduction. In emergency situations or when funds are lacking and the need is great, almost any material, with a specific gravity greater than water, has been used either as a temporary or permanent protective device against damaging waves or currents. Even for temporary protection, materials with a specific gravity of less than 1.5 are of little value. Other materials that may provide emergency or short-term protection may be so difficult to recover, or remove, as to be undesirable. Others may be environmentally undesirable due to hazards to bathers, visual or chemical pollution, or there may be the possibility that waves or currents may transport the material to an undesirable location or cause undue scour. New materials are continually being offered for coastal installations, but durability and resistance to fatigue and chemical breakdown are vital to the economic life of a coastal structure and, too frequently, only a long period of time will determine how the untested new material will function. 2. Concrete. a. General. Salvaged concrete may be used as found in its original form so long as lifting and transport equipment can handle it. It may be of reinforced or unreinforced concrete broken into sizes more easily handled, or it may be crushed and reduced to sizes ranging from sand to cobbles. b. Concrete Rubble. Concrete broken into sizes capable of being transported and handled by conventional rock-placing equipment can be used in the same manner as rock rubble for the armor and underlayers of rubble- mound structures. It is generally of two types--unreinforced or reinforced concrete. Unreinforced is preferred. If reinforcing steel is protruding, it is unsightly and dangerous to bathers or recreationalists climbing on it. If possible, protruding sections of steel should be cut off. In saltwater the exposed steel will corrode rapidly and split the pieces of concrete into smaller units and reduce their effectiveness to resist the force of waves or currents. (1) Revetment. The most common use of concrete rubble is in revetment. It may be used for armor stone or for the underlayer and design slope and sizing should follow the same design procedure as for rock. It must be kept in mind that concrete only has a specific gravity of about 2.3 to 2.5 and does not have the hardness of most stone so it will have a limited life. In place, it generally presents a somewhat unattractive appearance as compared to rock but, if in the wave wash area, will be abraded into a less angular shape and appear similar to waterworn rocks. It is acceptable as an underlayer beneath armor rock and near urban areas may be less costly. The primary use of salvaged concrete or concrete rubble in revetments is for emergency, low costs, or temporary revetment of an eroding bank or bluff. It is generally available for the cost of hauling and in many areas 309 like the coastline af the Gulf of Mexicg, the squtheastern United States or parts of the shorelines of the Great Lakes may be the only protective material immediately available. Sources of salvaged concrete for use in revetment are broken highway or landing strip paving, foundations for structures, broken piles or light standards, manholes, large sewer or water pipe. Thin slabs, particularly those reinforced with wire mesh, should not be used as they tend to form flat planes upon which other materials slide into deeper water and the exposed mesh is hazardous to recreationalists and the rusting of the mesh causes rapid deterioration. (2) Groins. The application of salvaged concrete is the same for groins as revetment but as groins are usually located in recreational areas the concrete is much less desirable from an esthetic and safety point of view. (3) Jetties. Concrete rubble is generally not desirable as armor material for jetties unless the jetties are located in small bays or lakes where waves are of limited height. The several thousand pieces of armor material required are usually not available in design size from broken concrete. Jetties are also usually designed for a long life and the concrete blocks tend to wear rapidly or disintegrate. Concrete rubble may, however, be used as graded core material. (4) Breakwaters. Concrete rubble is generally undesirable for the armor or underlayers of a breakwater unless it is in a small bay or lake. Wave action may be too severe and it is not feasible to obtain an adequate quantity of design size pieces. Concrete rubble is acceptable as a filler within the core section, as long as it is well mixed with the remaining core material to avoid excessive voids. c. Crushed Concrete. Equipment is available now to economically crush unreinforced concrete to most any size and gradation desired. Because of the need to completely rebuild miles of old highways, crushed concrete will, in some areas, compete with the cost of crushed stone. (1) Protective Structures. The principal use for crushed concrete in breakwaters, groins, and jetties would be for the core and bedding layer. Density is not so important here as for the cover layers but the crushed concrete should satisfy the same size, gradation and durability requirements as those established in the SPM {U.S. Army, Corps of Engineers, Coastal Engineering Research Center (CERC), 1977} for stone. The same criteria apply to the use of crushed concrete for use as filter layers in ~ revetments, seawalls and bulkheads, and special measures may be required to control the amount of dirt in a crushed concrete mix. (2) Roads and Parking Lots and Storage Areas. Crushed concrete is frequently used as a base course for roads, parking, or storage areas, particularly in commercial harbors. Properly graded, it is as effective as crushed stone and in urban areas may be less costly. d. Unbroken Concrete. Unbroken concrete would normally be so large as to be a supplement to cover stone. It would consist of foundation blocks, light standards, concrete piles, manholes and other reasonably compact concrete structures weighing between 0.44 and 88 kilonewtons (100 and 20 000 310 pounds). They are generally of an awkward shape to place and, if made of reinforced concrete, can have severe handling and corrosion problems, particularly if used in saltwater. They are generally unsightly and can be difficult to recover when no longer needed. Concrete barges or concrete hulled ships have, on a few occasions, been used in breakwater, groin or jetty construction. They may be incorporated into the mass of a breakwater or jetty, or may be used singly or in a line to act as a groin. In general they have not served well because their smooth sides and bottoms and large surface area compared to mass permit them to slide or tip out of position. The interior of these barges or ships may be difficult to fill with ballast and they are subject to the same deterioration problems of these slabs of concrete. Such barge or ship hulls can be extremely difficult and costly to remove or salvage. (1) Temporary or Emergency Protection. This is the most prevalent use of unbroken concrete units and many times does more harm than good. Unbroken concrete units are usually large enough that they should have an underlayer, or bedding layer, of smaller rocks, as in the design of a rubble-mound stone structure. Shapes such as light standards and pilings are usually too long and rigid to act as flexible and effective units, and in general there is little variety in size or shape to provide a well- graded section such as can be done with stone. Without a bedding layer, these units tend to work into the sand bottom and can be very difficult to remove. However, in emergencies they may be the only medium to high density material available and may be used pending later availability of properly graded stones. (2) Supplement to Armor Stone. Generally, for rubble construction, these unbroken concrete units are not available in a sufficient range of sizes to be used as armor stone. However, if they fit some of the design sizes for armor stone, and esthetics and the safety of recreationalists are not a controlling condition, they may be used in combination with armor stone to reduce costs. (3) Supplement to Core Stone. Unbroken concrete units are frequent- ly used in conjunction with core stone to simply provide bulk and reduce costs. Care must be taken to fill all voids inside and around these units so that they become an effective part of the core. Problems may be en- countered if their dimensions do not allow them to fit within the core ‘boundaries and they should not be placed so that large flat surfaces are near horizontal thus encouraging the sliding of other stones across them. 3. Asphalt. a. General. The primary types of asphalt mix used as a salvaged material in shoreline structures are the asphalt and concrete mixes and the asphalt and sand mixes. Both are used much in the same manner as salvaged concrete; i.e., as a substitute for stone. Depending on the proportion of asphalt, both the mixes tend to he of a lower specific gravity than stone or concrete and for this reason are less desirable. Both are less durable than stone or concrete. Because of its black to brown coloration it is less desirable from an esthetic point of view than concrete or rock. SI It is possible through heat processing to melt asphalt down and reuse it as a mixing agent but the cost is prohibitive and the material is of no value for shoreline structures. b. Asphalt in Rubble Structures. Broken asphalt concrete can be used in the underlayer if the same design criteria are followed as for stone. As a cover layer it is not desirable as it is of low specific gravity, is not as durable as stone or broken concrete, and due to its color and appearance is not esthetically appealing. Asphalt-sand has little durability, a charac- teristic that makes it undesirable in the cover layer. c. Crushed Asphalt Concrete. Crushed asphalt concrete or asphalt-sand is an acceptable substitute for stone as core or bedding material in coastal structures but must be used with care as filter material because of the difficulty of obtaining and maintaining an adequately graded mix to properly act as a filter. The most common use is as a base material for roads, parking lots, and storage areas in the same manner as discussed for broken concrete. Either broken or crushed asphalt concrete or asphalt-sand may be used as fill material so long as the voids can be filled. 4. Concrete Blocks and Bricks. a. General. Salvage material, consisting generally of hollow concrete blocks, cinder blocks and bricks, may be used in random placement. These materials are seldom used unless for emergency protection or of economic necessity. b. Concrete Blocks. These are generally hollow blocks salvaged from dismantled buildings or broken in production during the curing period. In the western United States these blocks are made of concrete, have a specific gravity of about 2.3 in seawater,and are not particularly durable. In the eastern United States they are frequently fabricated using cinders or slag for aggregate and are known as cinder blocks. These are even less durable than the concrete block and have a very low specific gravity (about 1.5 to 250) 6 (1) Rubble Structures. Concrete blocks are frequently used for emergency protection because they are frequently readily available for only the cost of transporting. They generally break down through handling and are of no value in the armor layer or in the underlayer. They are not durable nor are they esthetically acceptable. However, they can be used as temporary protection during an emergency in isolated, nonrecreational areas as long as it is realized that they must be covered with designed layers of stone that will act as a protective material. (2) Crushed Concrete Block. Concrete blocks will generally crush easier than broken concrete or stone and can be used in the same manner for bedding layers, filter layers, or as part of a base course for roads, parking lots, and storage areas. c. Bricks. Common building bricks have a specific gravity of about 1.9. They are not generally durable when subject to abrasion nor are they esthetically desirable. ; 312 Salvage bricks may be rejects from the kilns or salvaged from dismantled buildings or structures. They may be a whole brick, a broken brick, or a cluster of bricks still bound by mortar. (1) Rubble Structures. Salvaged brick is not desirable for either the armor layer or the underlayer of a breakwater, jetty, groin, or revetment due to its low specific gravity, lack of durability, and lack of esthetic appeal. It also tends to create slip planes. It may be used as core material as long as it is mixed with other materials and satisfies the general design criteria for core stone. (2) Crushed Brick. When brick is crushed it may be used as base course material for roads, parking areas, and storage areas in the same manner as crushed stone. It has limited value as bedding material because of the low specific gravity and tendency to reduce to sand and clay sizes. It is of almost no value as a filter material because of lack of durability and a tendency to break down and fill the voids necessary for it to act as a filter material. 5. Salvaged Ships, Barges, Railroad Cars, Automobile Bodies, Refrigerators, and Others. a. General. Because of their size and weight, it is always a temptation to use these no longer functioning objects to achieve "instant structures." In particular, some salvaged ships and barges might provide up to 300 meters (1000 feet) in length for a protective structure. Its weight may be several thousand tons. But there are difficulties involved in placement and perhaps even more difficulty in the task of removing these objects. b. Salvaged Ships and Barges. (1) Salvaged Ships. Salvaged ships are generally steel hulled, although there may be a few concrete-hulled ships from World War II, and they may be from 15 to 300 meters (50 to 1000 feet) in length. These ships are generally 20 to 50 years old and much of the internal equipment, particularly the heavy engines usually have been removed. The curved cross section of a typical ship's hull plus the partially streamlined bow and stern makes them difficult to place precisely and prevent shifting of position or capsizing. The general concept is to maneuver the ship into a predesignated location, _ sink it in place and fill it with sand, gravel, or rock to provide stability. The steel hull plates of these ships originally vary from 6 to 19 millimeters (1/4 to 3/4 inch) in thickness, have already been exposed to 20 to 40 years of corrosion, and have a very limited life as a partially sunken ship. The plates can be subjected in shallow water to abrasion by the sand that is constantly in motion and the force of breaking storm waves in shallow water can be considerable. Once the hull opens up the disintegra- tion of the ship can be very rapid and it will soon lose its effectiveness as a protective structure. Even as a temporary protective structure if the ship settles too deeply into a sand bottom, rolls over, partially disintegrates, or is no longer floatable, it can be extremely difficult and costly to remove. It is obvious that as the ships disintegrate and are moved by waves or currents 313 they can become a hazard to navigation, a danger to recreationalists, and very unsightly from an esthetic point of view. (2) Salvaged Barges. Barges may be of wood, steel or concrete. They are usually smaller than ships, more rectangular in dimension, and easier to place into position. They are usually flat bottomed and have a tendency to slide out of position under the force of storm waves. If positioned on sand, they are also subject to severe scouring action and may tilt or slide out of position. Like ships, they are usually many years old and seriously deteriorated before being salvaged. Wooden barges are the least desirable. They lack the deadweight of steel or concrete and once they start to disintegrate, the process is more rapid. Also, if filled with sand or gravel for stability they may even attain partial buoyancy as the waves remove this material. Concrete barges are unsightly and dangerous due to the mass of rein- forcing bars exposed as they deteriorate and break up. Steel barges, like ships, have relatively thin hull plates and through corrosion or wave forces deteriorate very rapidly, especially in seawater. (3) Breakwaters and Jetties. Neither salvaged ships or barges are recommended for breakwater or jetty construction. Wave action is generally too severe and, in the case of breakwaters, the waves strike broadside, the most unstable position. Even for temporary or emergency protection, salvaged ships and barges are not recommended due to the difficulty of removal. (4) Groins. There has been some limited success with the use of several barges in tandem. They must be securely fastened to each other and well seated on the bottom. Even so, because of deterioration, provisions must be made to either remove them or cover them with rock at a later date. (5S) Revetment. Salvaged ships or barges are not recommended for revetment. They are rigid structures and in an area of breaking waves will generate so much scouring action that more erosion may result than without these structues. c. Salvaged Railroad Cars, Automobile Bodies, Refrigerators, and Others. These are used mostly for bank or shore protection in nonrecreational areas. They are all unsightly and, while made of metal, generally do not - have much weight compared to total dimensions and are easily moved by waves or currents. Because of their rigidity and numerous flat surfaces they can cause accelerated scouring and may even accelerate the erosion process. Like other metals they are normally corroded before salvage and, if in seawater, the corrosion process is accelerated. Railroad cars and automobile bodies, in particular, will disintegrate within a few years. Their use is not recommended except in a nonrecreational area and only then as an emergency temporary measure, to be removed as soon as a long-term protective system can be implemented. 6. Rubber Tires. a. General. About 2 million rubber tires, too worn for further use on trucks and automobiles, and not capable of being recapped or retreaded, are 314 , available annually throughout the United States. While, as a material, rubber tires are strong and durable, they have almost no salvage value. Hence, they are generally available at very low cost or just for the cost of hauling. Rubber tires have been used for years as fenders on barges, work boats, and docks but it is only since about 1963 that they have been seriously considered as a low cost, and readily available, material for protection structures. b. Characteristics. Salvaged rubber tires have a specific gravity of about 1.2. They are tough, flexible, durable and almost inert to chemical reaction in either fresh or salt water. In fact, the critical strength factor of a scrap rubber tire system is not the "'tire'' but the fastenings and the mooring system. ch Uses. (1) General. Salvaged rubber tires have been used primarily to form floating breakwaters but they also have potential use for revetments, groins, bottom stabilizers, and fishing reefs. Experiments are underway to use them as an additive to asphalt concrete paving. (2) Floating Breakwater. Like all floating breakwater systems, the use of the floating rubber tire system is most successful where the need is to protect a basin area against short-period waves such as in bays, harbors, and lakes. Several different arrangements of tires have been used and model tested but the basic principles are the same. (a) Flotation. Flotation is provided either by entrapped air or by the filling of a part of the tire with urethane foam. The air system works only for tires held in a vertical position. A regular schedule of adding air to replace lost air or compensate for added weight due to sea growth or the entrapment of silt must be established. Tires are bundled together in modules of a workable size and weight and then the modules are assembled into a floating breakwater of design length, width, and depth. Other design factors are the density of the tire assembly and the allowable load stresses on the fasteners and the mooring system. (b) Fasteners. The scrap-tire assemblies have been secured by steel cable, galvanized iron chain, nylon rope, or (one of the most success- ful) scrap cuttings from conveyor belt material fastened together with nylon bolts, nuts and washers. The floating breakwater is a dynamic system, in constant motion, so it is imperative that an adequate inspection and mainte- nance schedule for these fastners and their hardware be established. Salvaged telephone or power poles may be used as inexpensive spreaders to frame the assemblage of scrap-tire modules. Poles and spreader framework may be specially treated to extend the useful life of fasteners; however, in view of the low-cost aspect of salvage systems generally this expense may not be justified. (c) Moorings. Standard mooring systems of steel cable or galvanized iron chain with anchors or anchor blocks are generally used to hold the breakwater units in place. Mooring stresses will depend on wave forces, density of the tire modules, width of the system,and depth of the SI'S water as related to the depth of the floating breakwater system. As with fasteners, a prudent inspection and maintenance schedule is mandatory. (3) Revetments. If the tires or modules of tires can be securely anchored to the bottom of the natural slope they can serve as revetments. With a specific gravity of only 1.2 they cannot be expected to stay in place of their own weight. They do not act as a revetment in the same manner as rock rubble; i.e., by completely absorbing or reflecting wave energy before it reaches the native bank material. The rubber tire revetment will only partially reduce the energy of the waves and, under persistant attack, increased turbulence may even accelerate the erosion of the native material. It may be feasible to use the rubber tires in conjunction with underlayers of rock to act as a revetment, providing the tires are securely anchored in place. (4) Bottom Stabilizers. Rubber tires are being used in parts of the Chesapeake Bay where waves are small and erosion is slow or intermittent; they apparently function by encouraging the growth of marsh grasses and the resultant increase in an accumulation of mud to stabilize the entire Mass. Some success in use of tires to control littoral drift has been reported in areas of low turbulence by simply anchoring rubber tires to the seabed to slow the bedload movement of sand either by currents or wave-induced movements in the littoral zone. This is obviously not feasible in the breaker zone of the open coast and the entrapment of sand outside the breaker zone would be slow and of minor quantities. This application may have particular merit in lakes, reservoirs or bays where surf is not severe. (5) Fishing Reefs. Modules of rubber tires, placed in deep water will, because of added surface and the many voids and crevasses, encourage the growth of marine plants and animals. The modules must be anchored in place but this is not as difficult as when used for floating breakwaters or revetments. 7. Uses in Coastal Construction. a. General. The use of recycled materials is very sensitive to the degree of emergency or lack of availability of new materials, the availa- bility of the recycled materials, and the suitability of the materials to’ accomplish the desired design objectives. In some cases such as floating breakwaters, the recycled material, in this case rubber tires, may actually be the preferred material. In every case, the conditions peculiar to the project determine the usability of recycled materials. When suitable, recycled materials can be used in the following types of coastal structures. b. Offshore Structures. (1) Breakwaters. Concrete rubble and salvaged asphaltic concrete can be used as a substitute for stone underlayers or cores but their lower densities must be considered when making the substitution. Crushed concrete can be an effective core material. Concrete blocks and brick can also be used as rubble in place of stone underlayer or core allowing for their lower densities. Crushed, these materials can be used for core material. 316 ’ Rubber tires are used to make floating breakwaters capable of attenuating short-period waves. Salvaged ships and barges should not be used as break- waters in the ocean or large lakes and have limited use as a type of caisson in that they are generally located at a remote station and towed to the site where they are sunk and perhaps filled with sand or rock to serve as break- waters or reefs. (2) Reefs. In addition to barges, automobile and railroad car bodies, broken concrete and rubber tires can be formed to trap sand for beach contouring and to encourage the growth of marine biota. Broken asphaltic cement, concrete blocks and bricks can all be used to create rubble-mound reefs. Below the wave and breaker zone such materials are more durable and more likely to serve successfully. c. Shore-Connected Structures. (1) Breakwaters, Jetties, and Groins. Salvaged concrete, broken asphalt cement, concrete blocks, bricks, salvaged ships and barges, salvaged railroad car bodies, and automobiles can be used as discussed for offshore structures but they all have severe limitations. (2) Seawalls and Bulkheads. Toe protection and backfill materials, where rock would normally be used, can be of salvaged concrete, asphaltic cement, concrete blocks or brick. These materials could also serve as aggregate for preplaced aggregate concrete. (3) Revetments. All the materials discussed in this section except the ships, barges and car bodies can be used to stabilize revetments. The finer particles of crushed materials would be suitable for filter blankets, the rest as rubble or cover material. (4) Piers and Wharves. Salvaged rubber tires make good bumpers and fenders for small craft using the piers and wharves. Tires are also good buffers between independent floats or structures that might otherwise bump or scuff each other in moving with tides, waves or currents. Broken concrete, asphaltic concrete and broken concrete blocks or bricks can be used as revetment to protect the shoreside embankment of piers or wharves. 317 XI. PROTECTIVE SYSTEMS FOR MATERIALS 1. Corrosion. a. General. To understand the reason for using coatings or applying cathodic protection, a brief review of corrosion fundamentals is necessary. These principles apply to any metal structure. Corrosion is defined as the deterioration of a material, usually a metal, or of its properties because of a reaction with its environment. Three conditions are necessary for metallic corrosion to occur: (1) There must be an electrical potential difference between two metallic electrodes, anode and cathode. This can exist because of metallic composition differences, metallic surface condition differences, or because of differences in the environment contacting the electrodes; (2) the contacting environment (electrolyte) must be electrically conductive with positively and negatively charged ions present; and (3) there must be a metallic connection between the electrodes. b. Corrosion Process. Corrosion is a natural process involving electrochemical reactions with a resulting flow of direct current from anodic areas of the substructure (corroding areas) to cathodic areas of the substructure, through the surrounding and contacting electrolyte (soil or water environment). A simplified diagram of the corrosion process on iron or steel in water is shown in Figure 90. The circuit is completed © through the metallic connection between anode and cathode. They both may be part of the same structure. This current flow is called galvanic current and usually is in microampere or milliampere quantities. With steel substructures, corrosion (loss of metal) takes place only at anodic areas as the result of current flow into the electrolyte from anodic areas. In the case of iron or steel, metal loss amounts to about 90 newtons (20 pounds) per ampere-year of current flowing from the metal into the contacting electrolyte. Loss of metal is directly proportional to the amount of current. One milliampere of current leaving the substructure from one point into the electrolyte will cause penetration of 9.5 millimeters: (3/8 inch) steelplate in less than 1 year. See Table 40 for corrosion rates of other metals, including anode materials. With iron or steel substructure the electrochemical reaction prevents corrosion of areas where current flows from the electrolyte into cathodic areas of the substructure. Anodes, cathodes, and corrosion current as related to steel in water are shown in Figure 91. c. Corrosivity of the Environment. In air the corrosivity of the environment on a structure will depend on the temperature (ranges and mean averages), relative humidity, wind conditions, proximity to the water, rainfall, and chemical fumes (from cargo or nearby plants). Corrosivity generally increases with increases in temperature, relative humidity, wind velocity (particularly off water); with closeness to the water; with increased rainfall; and with higher concentrations of chemical fumes. 318 —= CONVENTIONAL CURRENT FLOW (+ TO -)—~— —=— ELECTRON FLOW ~—— H+ OH- 2e7+2Ht——H2 B- SIONS Fe —=Fet+t+2e- Fe+++ 20H-—=Fe (OH)2 4e- +02+H20—= 4 OH- ate CONVENTIONAL CURRENT FLOW Fe—— hem 2en Fet++20H-—=Fe(OH)2 2e-+2Ht——H2 CATHODE ~STEEL ANODE Ht ———— OH ION. FLOW Figure 90. Corrosion process. If the structure is to be immersed, the corrosivity will depend on the temperature of the water, chemical composition (salt content, dissolved oxygen and the presence of other chemicals), velocity of the water (movement by tides, waves, gravity, etc.), and splash zone effects (a combination of mechanical and corrosive effects). Corrosivity on immersed or partially immersed structures generally increases with increases in temperature, increases in corrosive chemical content, increases in fluid velocity and in the splash zone. It should be noted that high purity water such as distilled water or deionized water is a special condition and can cause coating to blister or delaminate. BIE) Table 40. Corrosion rate of some common metals. Consumption Rate i Metal (newtons per ampere-year) Lead Copper Tin Zinc 1 Iron Magnesium Aluminum Carbon! 8. High Silicon Iron? less than 0.44 Magnetite Fe30,,2 less than 0.044 5 Lead-Silver? less than 0.044 5. (seawater) Platinized Titanium less than 0.000 044 (seawater) 1 (seawater) ONDOWNWA AD 1Galvanic anode material 2Impressed current anode material PIPELINE CORROSION — eee CATHODE ————> CURRENT ——~> ANODE a. Single cell PIPELINE CATHODE CATHODE ANODE ANODE alien > = Ta ee SS SS b. Multiple cells Figure 91. Corrosion process in pipelines. 320 d. Corrosion Prevention. The corrosion process on a given structure can be prevented or stopped if any one of the three conditions necessary for corrosion can be eliminated. The principal methods for preventing or mitigating corrosion are described below. (1) Coatings. A perfect coating will electrically insulate the anode and cathode areas from contact with the electrolyte, preventing flow of corrosion current. As is well known, a perfect coating is an impossi- bility for anything other than a laboratory-scale project. Also, all coatings disintegrate in time, imposing an ever-increasing area of poorly coated or bare metal. Cathodic protection is an ideal way to deal with coating discontinuities (holidays) and poor coating in general. Coatings (with cathodic protection) are feasible for practically any subsurface structure. An exception would be the underwater parts of offshore oil production platforms where coating repair or replacement would not be possible. (2) Insulated Joints. Insulating joints between metal plates or piping joints will minimize stray current or galvanic corrosion where it interrupts corrosion current flow. [In this application, the metallic connection between widely separated anode and cathode areas is broken by the insulating joint. Insulated joints also serve to separate dissimilar metal areas, as well as to separate cathodically protected areas from unprotected areas. (3) Cathodic Protection. The corrosion process on a given subsurface structure can be prevented or stopped by supplying an excess of electrons to all subsurface parts of the structure. The result is that the structure becomes all cathode because of the electrons provided by forcing direct current to flow through the contacting electrolyte (water or soil), from a nearby subsurface source (anode) onto all subsurface parts of the structure. Hence the name, cathodic protection. When the current is adjusted properly, it will counteract corrosion current flowing into the -electrolyte from the substructure with an opposing and slightly more than equal flow of current flowing from the electrolyte into the substructure. Loss of metal has been transferred from the protected substructure to the external anode which will require occasional replacement. 2 (COaitames. a. Introduction. Environmental conditions affecting coastal structures range from mild to severely corrosive. To provide suitable service life for coastal structures, protective coatings are usually required, ranging from little or none (other than decorative painting) to complex and extensive multicoat systems. Specific coating demands depend upon type of substrate to be coated and its environment. 32l This section will cover the basic design considerations that must be given to the structures to be protected and to the selection, application and inspection procedures necessary to provide a protective coating system with years of dependable service life. Repair, rehabilitation, proper maintenance procedures and other important facets, including economics, are also described. Protective coatings are designed primarily to isolate metal surfaces from exposure to corrosive elements. Coating thickness will vary from 50 to 75 micrometers (2 to 3 mils) for simple alkyd coating systems to 380 to 760 micrometers (15 to 30 mils) for certain high build coal tars, coal-tar epoxies or urethanes (1 mil equals 25.4 micrometers or 0.025 millimeter; where any conversion in a discussion results in numbers less than 0.1, micro- meters will be used). Conventional paints, surface preparation and methods of application should not be used in corrosive areas of coastal structures. Only high performance protection coatings such as epoxies, zinc rich, chlorinated rubber, and polyurethanes must be considered. Products selected for use should be resistant to the environment and capable of serving as a barrier between the environment and the substrate. Writing appropriate specifica- tions to cover all facets of the work will play an important role in terms of obtaining the protective coating job desired including, particularly, cost per unit area per year of service life. b. Design and Specifications. In the design of new structures, it is important to consider surface requirements for ease of coating application and effectiveness of coating. The design should (1) provide smooth, flat, easily curved surfaces, and (2) avoid overlapping surfaces, edges, back- to-back structures (brackets, beams or L's), riveted surfaces, sharp protrusions, and weld splatter (see Fig. 92). _Like other personnel in any design and construction organization who are engaged in translating an owners requirement into design and the design into a structure, the protective coating specifier must give careful consideration to all aspects of the coating work requirements. The speci- fication must detail coating selection, surface preparation, coating application, coating inspection, touchup, and repair to ensure a successful job. 2 c. Generic Classes. Numerous coastal marine coating tests and surveys of field applications have been made. Table 41 lists some of the coating systems used for various surface substrates. In the discussion which follows, various uses and precautions are presented for each coating system, with a brief description of chemical composition and properties. Coatings are composed of many raw materials. These materials can be divided into three categories--vehicle, pigment, and additives as shown in Table 42. The vehicle or liquid part of a coating is composed of resin, solvent, and plasticiser. The vehicle resin contributes to many of the basic properites of a coating including water resistance, chemical resistance, cure time, elongation, toughness, and adhesion to substrate. 322 SPECIFICATION CONSIDERATIONS cabs SEAM WELD SE eX WELDS Ye ROUND CORNERS ANNES | BACK- BACK DO POCKETS OR CREVICES. ALL CONSTRUCTION INVOLVING POCKETS OR CREVICES THAT WILL NOT DRAIN OR THAT CANNOT BE PROPERLY BLAST -CLEANED SHOULD BE AVOIDED. ROUGH PINHOLE ae UNDERCUT \_ crip sMooTH DO DONT CONTINUOUSLY WELDED JOINTS. ALL WELDED JOINTS SHOULD BE CONTINUOUSLY WELDED. ALL WELDS SHOULD BE SMOOTH, WITH NO POROSITY, HOLES, HIGH ) 2 ’ SPOTS, LUMPS OR POCKETS. GRINDING SHOULD BE USED TO ELIMINATE POROSITY, SHARP EDGES AND HIGH SPOTS THAT DO OCCUR. aes WELD iii \__ orn D SMOOTH \— wep FLUX DONT REMOVE WELD. SPATTER - ALL WELD SPATTER SHOULD BE REMOVED. ae peer \_ 1/8" Rapius DO SHARP CORNER ——% DONT MINIMUM RADIUS OR CORNERS. ALL SHARP EDGES SHOULD BE GROUND TO A MINIMUM RADIUS OF 1/6" (3.2mm). DO_ Figure 92. Examples of design details to aid coating application. 323 99UD}S!1SA4 UO!SO1I0D 41D} PUD AjyI{1}ONP poo ‘yawtsd Axoda 1aa0 BursayyDam poob soy adfj d140ydIy yuBijuNS ul syHJDUD ing SaduUD}SISa4s jDIIWaYD PUD A4l|iqo4np poog “+dn payonoy Ajtsoe SAjijiqounp pood "}009d0} JNOUJIM ABJOMDSS UI B41] PAJwiy ‘SyuDESISa41 UOISDAGD Kid *ssoib poob ‘SAyuo sjuawuodstauea piiw 404 *Ajuo yuawuostAua pjiw 104 ‘Kjuo U@9WUOJIAUa PjlwW JO4 *@2uD4SISa4 |DD!wWaYyd puDd AyyIqoD4Np POD *@OUDJSISAs JOXIWAaYd PUD AjtjIgo4inp pood *syuanjos BuosyS 0} 100d ‘194;0M 0} |B9U04SISA4 Pood “SjugmUOsJAUa Pessawwi 4O dwOp Ajsnonut{UuoOd uo: JaAeN “SJUBWUOSIAUD BAISOIIOD AOA U! 949849U09 104 *BulyooidsajDM 20) Pood *X38$O07 DNAs SD aWwOS “UOl}D4JQUad JB}OM BINPDS |jIM S}OII9}OUW BSay) yO SJDOd |II14 *Bulyoo01dsajOM 4103 POOS °X9}07 DAs SO aWOS “¥|DYD aSOOj ||D aAOW AI Jsnw {SadDy4NS aS4D09 uo pooh si Buiysnaq $ pasjddo Ajisog -patjddo Ajispe £yj0yd JulDd pud pooMm pasaytoeM jo BulLgam JOOd *ss0jb poob ‘buyjam poos *saiy4adosd JO Apalson dA16 SUOI}OIIOA “Bulyyam pood "tyos $6ulkup mojs fy;oyd ,ULDd puD POOM pasayjoOaM yo Bulyyam poog ~19utad x9}0] 10 ‘pAXIO ‘110 4940 patjddo aq uo “1440S 40 psdy aq Aow “yyoSs AjaAtjoja4 Puo Bulkup moys Ayposauay S}UaWWOD }UI0d a}04ISqGnS "soq.erysqns jUsTeFFIp uo posn ATuoumod ssutzeod Jo sodA] ‘Tp OTqeL Jaqqny payoulsojug e@uoysaun Kxod3 |AuIA du!IZ d!1u06i0u| PAYTY BUOdIIIS PANY 110 auoysosNn Axod3 [Aun PANY *pAULA 4aqqny paejsOulo|YyD X9407 jAUIA XO9}D7 DAuoy 4aqqny pe}oOulsojyd x9yo7 |AulA X9JO7 D1Aaoy (21)A4d 7 40 |AUIA) XO4D7 PAM YOdINIS PANIV 110 (9ttA19 30 JAUIA) XaJO7q ~ PANIY 110 1924S PuD UO] 10140}xg }aaIs pud uodj 401194U4 Aauosow puod “aya4Uu0D 401494xq pidog HOM puod S194SDjd *KsuOSOW 40119} UY POOM 40119}x9 POOM 40149} u| 324 Table 42. Coating components. VEHICLE RESIN PLASTICISER SOLVENT PIGMENT ADDITIVES Prime Surfactants Glycols Extenders Drying Agents Coatings are usually named or designated by their resin systems. For example, an alkyd coating contains an alkyd resin, an epoxy coating contains an epoxy resin, and a silicone alkyd contains an alkyd resin as the primary resin system with additions of silicone resins. Plasticisers are added for modifying the properties of the resin. Solvents are used for dissolving or dispersing the resin for manufacture. Solvents are also useful for develop- ing and controlling application properties of a coating. For example in a cold climate, the solvent must be volatile enough to evaporate at low temperatures. Conversely, in tropic or desert climates, the solvent must be slow enough (less volatile) to allow the coating to flow out and properly cover the hot surface before it volatilizes. Prime Dilutents Color Corrosion Inhibitor Anti-Skinning Agents Mineral Spirits MEK Toluene The pigments are the finely ground solids which are added to give coating body, color, and corrosion-inhibitive properties. Special additives are added, usually in small amounts, to give the coatings many special properties. Table 43 lists generic coating types suitable for use on concrete and steel (both immersed and nonimmersed). Selection of a recommended coating system for a given service condition is determined from specific properties of coating types, described below. 4 (1) Alkyds. Alkyds are formed when 011 is combined chemically with glycerol phthalate. They cure by reaction with oxygen and have excellent wetting properties and fair to good weather resistance. Alkyds have poor resistance to acids and alkalies and only fair abrasion resistance. They should be used only for mild environments in selected harbor locations. They should not to be used where surfaces are continuously damp or immersed in water. (2) Silicone Alkyd. Silicone alkyds possess properties similar to alkyds as defined above but possess somewhat better heat resistance, weather resistance, and gloss retention. They cannot be used for immersion. Also they are softer and are less resistant to abrasion. © 325 Table 43. Recommended coating systems. Type of Surface Coating Type Concrete Coal Tar Coal -Tar Epoxy Steel (Nonimmersed) Alkyd Silicone Alkyd Silicone Acrylic Coal Tar (Good) Coal-Tar Epoxy (Good-Excellent) Epoxy (Good-Excellent) Urethane (Good-Excellent) Vinyl Zinc Rich Steel (Immersed) Coal Tar Coal-tar Epoxy Epoxy Epoxy Phenolic Phenolic Vinyl 326 (3) Modified Alkyds. Modified alkyds have additional resins added (such as ester gum, phenolic, styrene, vinyl, acrylic and chlorinated rubber) to improve properties such as weather resistance and corrosion resistance. They may be used for some coastal structures, however, because of the limited corrosion resistance of alkyds, immersion service or exposure to corrosive environments is not recommended. (4) Acrylic (Solvent Base). Acrylic coatings may be formulated as solvent-base or as water-base materials. The solvent-base coatings are composed of copolymer acrylic resins in an aliphatic hydrocarbon solvent. They cure by evaporation of solvents and in some respects possess the toughness and corrosion resistance of a baked enamel. Acrylics have good resistance to general weathering. They have excellent gloss retention and color stability. Their resistance to marine atmospheres and corrosive environments is good. They have good impact resistance and fair heat resistance. Acrylics may be used as topcoats for epoxy, modified alkyd, zinc rich and universal primer. They are not recommended for immersion. (5) Acrylic (Water Base). The water-based acrylic products are widely used for masonry, stucco, or wood for both interior or exterior application. They are also used to a limited extent for metals. Because they are water based they are nonflammable and may be used in fire hazard areas. They are quick drying and may be easily cleaned with water. Acrylic water-base coatings have excellent color retention, good flexibility and toughness, and are easy to repair. They have only fair corrosion resistance. Acrylic resins are used in conjunction with other resins to improve color stability and general weathering resistance. (6) Chlorinated Rubber. Chlorinated rubber coatings are composed of rubber polymers chemically treated with chlorine in a blend of solvents. They cure rapidly by solvent evaporation. Chlorinated rubber coatings have fair to good corrosion resistance to marine and chemical corrosion. They resist most dilute acids, alkalies and salts and have fair weathering resistance and color stability. They are suitable for immersion in salt and fresh water to 49° Celsius (120° Fahrenheit). Chlorinated rubber coatings have fair abrasion and impact resistance but possess only poor resistance to organic solvents. : (7) Coal-Tar Coatings. (a) Mastics and Coal-Tar Cutbacks. Coal tar is a byproduct of the coal coke industry and has outstanding water resistance. For this reason it has been found to be an excellent coating material for use on Many coastal structures. Its high resistance to moisture makes it useful for immersion or for the splash zone service. It is one of the finest coating materials for resistance to water or moisture. For this reason, it is frequently used for protecting steel or concrete in immersion. Coal-tar products are usually applied by spray because of their heavy consistency, but touchup is frequently handled by brush. Additional thinner may be added when the coating is applied by brush. i VATE (b) Modified Coal-Tar Coatings. Coal-tar coatings are frequently modified with other materials such as epoxy or polyurethane. The modified products have the excellent water resistance of the coal tar with the improved toughness and solvent resistance of the modifier. Properties of coal tar and the modified materials are as follows: (1) Coal-tar properties: low cost, excellent resistance to water, low moisture vapor transmission, poor resistance to organic solvents, and poor abrasion resistance and toughness; (2) epoxy properties: tough, chemical resistance, and solvent resistance; and (3) urethane properties: elastomeric and abrasion resistance. Two component coal-tar epoxy and coal-tar urethane coatings are dis- cussed. Coal-tar epoxy systems contain coal tar, pigments, solvents, epoxy resin, and either an aliphatic or aromatic amine or polyamide curing agent. Coal-tar urethanes contain coal tar, pigments, solvent and reactive urethanes. These "chemically cured" coal-tar coatings can be applied in one coat to dry film of 0.13 to 0.64 millimeter (5 to 25 mils). Most coal-tar epoxies have excellent adhesion, abrasion, and impact resistance. Their resistance to immersion effects in salt and fresh water is excellent and they withstand a wide range of chemical corrodents. Proper measurement of two components is mandatory for proper cure and coating properties. It is recommended that these coatings be mixed by use of power mixers. Subsequent coatings must be applied within manufacturers’ specified time and temperature limitations to avoid delaminization between coats. The coal-tar epoxies have a variable pot life when mixed depending on the temperature. Repaira- bility is a major problem and color is limited to black. They tend to chalk lightly in sunlight and weather and lose their original black gloss within 6 months to 1 year. (8) Epoxies (Catalyzed). Epoxy coatings are based on epoxy resins and are supplied as two component materials. One component. contains the epoxy resin, the other the curing agent. The two components must be thoroughly mixed before application. A broad spectrum of service conditions is covered by a wide variety of materials based on these versatile resins.- Amine or polyamide type curing agents are most common. Epoxies have excellent durability and toughness and possess high chemical and moisture resistance. They resist strong alkali, and have excellent adhesion proper- ties and abrasion resistance. They may be used in marine environments and are not damaged by moisture or immersion in water. Epoxies may be used in conjunction with special fillers to make mastic- like materials which find applications as concrete grouts, surfacers or "bug hole’ fillers. These mastics or grouting compounds may be applied as heavy coats by trowel or in some cases by spray. They are used in marine application to protect concrete or steel in the splash zone. Heavy layers of the mastic are built up in the splash and tidal zone. Layers of glass fabric may be introduced, between coats of mastic to add-strength to the splash zone coating system. Application is sometimes by hand in a process 328 known as "palming" (Fig. 93). Gloves should be worn when handling epoxy materials as many people have a toxic reaction to epoxies. WELD OR APPLIED BY PALMED EPOXY a Figure 93. "Palmed" application of epoxy underwater coating. Certain epoxy polyamide coatings and mastics will cure on moist surfaces, or even under water. It is this property that allows these materials to be utilized for coating and for repairing wet or submerged structures which require protection. Epoxy coatings have excellent corrosion resistance to most chemicals. They perform well in alkaline media but are only fair in contact with acids. Because of their inertness they are sometimes difficult to repair or topcoat. Because of adhesion problems, very few coating Materials will adhere to a well-cured epoxy. Epoxy coatings tend to chalk and for this reason, colors fade, particularly dark colors. The lighter colors are most frequently specified for use where the coating will be exposed to sunlight and weather. To summarize, epoxy coatings have excellent corrosion resistance and toughness, but are fair to poor in-weather re- sistance. (9) Epoxy Phenolic. Epoxy phenolic coatings are epoxy-type coatings which have been modified by the addition of phenolic resins. The phenolic resin adds corrosion resistance as it promotes cross linking and bonding of the epoxy resin as illustrated in Figure 94. With the increased resistance of the epoxy phenolic coatings to attack by corrosive chemicals or environments, these materials find application as linings for tanks, barges, ships, and piping. i 329 PHENOLIC Figure 94, Cross-linked epoxy phenolic. The disadvantages of epoxy phenolics, as compared to epoxies are: (a) Increased brittleness of coating; (b) lack of toughness and thus more subject to damage upon impact (cracking, shattering, delamination) ; (c) requirement for heat in curing (not true with all epoxy phenolics) ; (d) lack of availability in high build formulations; and (e) slightly more difficult to repair and topcoat due to adhesion problems {see paragraph (8)}. (10) Phenolics. Phenolic coatings include baking phenolics of the alcohol soluble type and phenolics of the oil soluble type in combination with drying oils. The baking phenolics have excellent resistance to corrosive chemicals, acids and caustics. They require baking for curing (cross linking). The baking phenolics form tightly cross-linked coating films with exceptionally high corrosion resistance, which is higher than the epoxy-phenolics. Because of their tight cross linking they are brittle and subject to damage and delamination if subject to impact. These materials are used as linings for tanks, barges, and piping. The phenolic coatings designed for atmospheric service are made from phenolic resin combinations and drying oils. These, at one time, were considered the best air-drying coatings for water resistance and weak chemical resistance; they were used extensively as marine maintenance coatings. They are still considered superior to most alkyd coatings in 330 hardness, abrasion resistance, and chemical resistance. Their limitations include somewhat less weather resistance than certain alkyd coatings. They possess only fair gloss retention and are applied at comparatively low film thicknesses. They also require good surface preparation for best performance. Many phenolics become brittle with age. (11) Polyurethanes. These generic class products, more commonly called "urethanes," are usually comprised of either moisture-cured, single- packaged systems, one single package which requires heat to cure, or two- packaged catalyst-cured types. All urethanes contain isocyanate. The single package systems include one which cures by reaction with moisture and one which is cured by heat. The two-packaged systems are cured by reaction with a curing agent such as an hydroxl-bearing polyols. Due to the wide variety of formulations available, the selection of the proper urethane for a specific job is often difficult. Chemical resistance (fumes, splashes, and spills), especially with those cured by hydroxl-bearing polyols, is very good. Others may be somewhat limited in this respect. These type coatings are best known for their toughness and resistance to abrasion and impact. The urethanes based on an aliphatic resin possess outstanding resistance to sunlight and weather including excellent gloss retention. These are used extensively on ships and aircraft where color retention is important. Other urethane formulations based on aromatic urethane resins have poor weather resistance. They should not be used as exterior coatings. Adhesion properties are fairly good to properly primed metal or direct to masonry. Urethanes also adhere generally well when directly applied to fiberglass materials. There are some formulations which have high build properties. Many urethanes have excellent low (eS NAENEL LE cure character- istics and may be used at temperatures as low as 2 Celsius (35% Fahrenheit). Urethanes have excellent flexibility and elongation properties. Because of the inertness of the two-component polyurethanes, repairability and recoating can be difficult due to adhesion problems. (12) Vinyls. This class includes all polymers and copolymers of vinyl chloride with vinyl acetate and vinylidene chloride. They are single-packaged coatings and cure by solvent evaporation. Vinyls are also processed with oil base materials such as alkyds, phenolics, and acrylics. Most offer good overall corrosion resistance. They are somewhat similar in this respect to chlorinated rubber. Vinyls withstand high humidity and are comparable to epoxies in many respects in resistance to salt atmospheres and immersion in water. They have good abrasion and impact resistance. Flexibility and elongation properties of vinyl coatings are good. Vinyls are among the best coatings from standpoint of resistance to oxidation. Many have good gloss retention. Their repairability is very good, and they usually present very few problems on recoating. Resistant to most solvents, however, is poor and they have a limited heat resistance. (13) Inorganic Zinc. These products are formulated with metallic zinc dust, at relatively high pigment volume concentration, with inorganic binders. Metallic zinc content is 60 to 90 percent by volume in the dried 33! film. As a single coat system they have outstanding carrasion resistance on coastal structures for protecting metal exposed to aggressive marine atmospheres. They may be topcoated to produce a coating system with an even greater anticipated service life. Inorganic zine coatings may also be used in industrial environments. In mild industrial environments they may be used without topcoats. One application, which has found wide usage in the past, is lining hydrocarbon tanks, both on ships and shore. Inorganic zinc has excellent abrasion resistance and is often used as preconstruction primer. It must be topcoated for use in aqueous immersion. Zinc coatings offer excellent resistance in the splash zone to saltwater and to freshwater. Zinc-rich primers are often used as primers for organic topcoats such as chlorinated rubber, vinyls, epoxies, urethanes, and certain acrylics in more aggressive chemical atmospheres. It must also be topcoated for continuous immersion in water. Surface preparation require- ment is stringent and application requires skilled workers. (14) Organic Zinc. This classification of coating is composed of zinc dust with organic binders such as epoxy resins. Zinc dust content will vary between 45 and 80 percent by volume in the dry film. Performance of the coating is related to the percentage of zinc in the final dry film. Generally, the more metallic the zinc, the better the performance. Organic zinc coatings also show excellent resistance to high humidity splash and spray conditions of both fresh and salt water. Abrasion resistance is somewhat less than the inorganic zinc primers. The organic coatings will tolerate mildly alkaline atmospheres. They are often preferred to "inorganic" zinc as primer for chemical atmospheres because surface preparation and application procedures are less critical. (15) Underwater Curing Coatings and Mastics. These materials are two-component 100 percent solids polyamide cured epoxy nonshrinking compounds (sometimes combined with appropriate fillers), designed to chemically displace water on the surface and form a tight bond. Extensive and careful laboratory and field tests, combined with experience information, have shown that good protection can be provided to in-place underwater structures with these mastics. They are applied by gloved hand (palming) or trowel to a dry film thickness of 3.2 to 6.4 millimeters (125 to 250 mils), and cure while under, water after several days. Tensile strength, adhesion, impact strength and abrasion resistance are fair to good. They can be used as patching com- pounds to seal metal, concrete, wood, fiberglass and many other substrates specifically in situations where the surface is damp, wet, or under water. The surface preparation recommended is sandblasting for best results. Costs of material and application are very high, $54 to $162 per square meter ($5 to $15 per square foot). (16) Other. There are other special coatings that may be used from time to time for certain applications for coastal structures. These materials are combinations and modifications of the above generic coating classes. They will not be discussed in detail in this report. These coatings include vinyl polyurethanes, epoxy/fiber reinforced mortars and coatings, polyester/glass flake combinations, glass flake/coal tar/epoxy, 100 percent solids urethane/elastomeric membranes, catalyzed hypalon/coal 332 etqeottddy 10N = YN IO0gd = d ITeyq = J poop = 9 JUOTTOOXY = J ysty s8UTIeOD YITY- UTZ uN TPoW STAUTA “OT ysty souey and og YSTH-unt pow soTTOUdUd YsTH-uNTpoep sotrtoueyg Axodg uN T pow sotxody 2%) uNnT pep setxodg 1e]-[eo9) aG MOT S$3UT1eOD IPL-TeOD ‘Ly uNTPoW-MOT Jeqqny pedeurroT yD unT pew ou. By SPpAYTY 9UOSTIIS “2 MOT d d d d SPAMIV ‘T a o & § 6 5 Lo} =) =) 4 4 G wo 3 7) -s) u [=] S Ge} =I & H oO oO fo} ole =) sey (o) [ov oO 77) S| ‘4 (= {S| y ‘fd 5 f= Fs) n eo oO (o) =< ce Oo (0) oO v ood Sie 1 R aL { (log, ) -1} (1) where R = resistance of vertical anode or backfill to ground or water in ohms L = length of anode in centimeters a = radius of anode in centimeters op = electrolyte resistivity in ohm-centimeters This can be simplified to: Rvs en) (2) 0.0129 So ol; Taryies D where Rv = resistance of vertical anode or backfill column to ground (soil or water) in ohms L = length of anode or backfill column in feet D = diameter of anode or backfill columns in inches o = electrolyte resistivity (backfill, soil, or water) in ohm-centimeters (a) Anode Installed in Backfill Soil. If a single anode is to be used, in soil, the internal resistance (anode to backfill) should be considered. Internal resistance is not a factor when the anode is installed 362 without backfill, such as in seawater. This will depend on the type of hackfill used which will, in turn, depend on whether the anode is to be of galvanic or impressed current type. For an impressed current anode with carbonaceous backfill, a backfill resistivity of 50 ohm-centimeters may be used. Assume a graphite anode 7.6 centimeters (3 inches) in diameter and 1.5 meters (5 feet) in length is to be centered in a vertical backfill column 20.3 centimeters (8 inches) in diameter and 2.1 meters (7 feet) in length (see Fig. 100). Resistances are calculated for the anode and for the backfill column using equation (2) with p = 50 ohm-centimeters. The difference between the two values represents the internal resistance of the anode (0.213 - 0.128 = 0.085 ohm). For most conventional.impressed current anodes used singly, a figure of 0.1 ohm may be safely used. Where more than one anode is to be connected in parallel, the internal anode resistance for the group becomes the single anode internal resistance divided by the number of anodes in the group. If the number of anodes to be parallel connected is more than three or four, the internal resistance becomes negligible. The same method is used to calculate the internal resistance of a single galvanic anode (see Fig. 101). Here the backfill resistivity will be higher, with a resulting higher internal resistance. (b) Anode Installed in Water. For suspended vertical anode installations in water, the anode should be installed so that the top of the anode is never less than 1.5 meter (5 feet) below the water surface. Refer to tide data. The bottom of the anode should be 1.5 meters above the channel or marine bottom. Header cables should be far enough above the water surface to ensure no water contact. In protected areas this would be a minimum of 3 meters (10 feet). Header cables would have to be at much greater height for open-sea areas. This will require anodes with leads large enough to permit connection to the header cable with no underwater splicer required. In some cases anodes may require installation in perforated nonmetallic pipe to ‘prevent damage by water movement. (4) Calculating the Resistance of Anode Groups. Usually anodes will be used in groups, installed in a line, connected in parallel to a header cable which in turn is connected to the substructure to be protected (galvanic anodes) or to the positive output of the power source (impressed current anodes). A calculation of the overall resistance of the parallel- connected group (usually termed ''anode bed'' or "ground bed'') will be required. The effective resistance of the group, differing from normal parallel elec- trical circuits, will not be equal to the resistance of one anode divided by the number of anodes in the group. This applies to marine installation also. Due to mutual interference between anodes the resistance of the group will always be higher than that determined by parallel electrical circuit calculations, varying with the number of anodes, anode spacing, and electrolyte resistivity. Several methods have been used for the calculation of parallel anode resistance. One method utilizes the following equation: _ 0.001566 2.94 1. Ry = * 1(2.303 log = + At 2.303 log 0.656 N)} (3) where Rv = resistance to electrolyte (soil or water) in ohms of | the vertical anodes in parallel 363 INSULATED aaa CABLE TO INSULATED CONNECTION FILL CABLE TRENCH AND TOP OF POWER SOURCE AND TO BETWEEN HEADER CABLE Nees AUGER HOLE WITH TAMPED OTHER ANODES iN. GROUND BED AND ANODE PIGTAIL WIRE ARTH Aarne COMPLE TING CONNECT ION INSULATED CONNECTOR WIRE FURNISHED WITH ANODE .05X1.5M OR .O8XI.5M HIGH SILICON CAST IRON OR GRAPHITE CARBONACEOUS BACKFILL MATERIAL; WELL TAMPED AUGERED HOLE FOR ANODE AND BACKFILL Figure 100. Anode in carbonaceous backfill. 17 POUND PACKAGED of : : : MAGNESIUM ANODE J. 1.5 METER LONG ; DE OF iC OR BACKFILL, PACKAGED, MAGNESIUM SUPPLIED WITH ANODE : s AUGER HOLE CLAY-GYPSUM BACKFILL MIXTURE Figure 101. Anodes in other backfill materials. 364 0 = resistiyity of electrolyte in ohm-centimeters Zz i} number of anodes in parallel Ee Wl length of anode (or backfill column) in meters D = diameter of anode (or backfill column) in meters S " anode spacing in meters The resistance of the anode group is the sum of Rv and the internal re- sistance of the group, that is, the internal resistance of a single anode divided by the number of anodes in the group. Equation (3) may be used to construct a chart for use with the anode size and backfill size to be used for a particular project. Such a chart, based on impressed current anodes 0.05 meter (2 inches) in diameter and 1.5 meters long in 0.2-meter (8 inch) by 2.1-meter (7 foot) backfill columns of 50 ohm-centimeters resistivity, 1s shown in Figure 102. A similar typical design chart for galvanic anodes is shown in Figure 103. Note that both charts are based on electrolyte resistivity of 1 000 ohm-centimeters. Anode (or backfill column) resistance to electrolyte is directly proportional to electrolyte resistivity. For example, consider 15 anodes in parallel at 7.6 meters (25 feet) spacing in 2 200 ohm-centimeter soil. Anode (in backfill) resistance in 1 000 ohm-centimeter soil, shown on the chart in Figure 103, is 0.233 ohm. Resistance in 2 200 ohm-centimeter soil = 0.233 x 2 200/1 000 = 0.513 ohm. To this add the internal resistance of the group. From use of equation (2) the internal resistance of one electrode is 0.106 ohm, making the internal resistance of the group (0.106/15) = 0.007 ohm, a negligible amount. The total resistance is 0.520 ohm, but 0.513 ohm could be used safely. (5) Calculating Resistance in Cables. Cathodic protection design also requires a knowledge of the resistance of various sizes of copper wire or cable most often used in anode installations. Resistance data and common use of some of the most commonly used sizes are shown in Table 57. (6) Calculating Anode Lifespan. If current output of a galvanic anode of any given weight is known, its approximate useful life can be calculated. The calculation is based on the theoretical ampere hours per newton of the anode material, and its current efficiency (see Table 52). Also involved is a utilization factor, which may be taken as 85 percent. This means that when the anode is 85 percent consumed it will require replacement. This is because there is insufficient anode material remaining to maintain a reasonable percentage of its original current output. Expressions for determining individual anode life for different materials are presented below with efficiency and utilization factors expressed as decimals: (a) For magnesium: anode weight 0.026 ° in newtons ° efficiency ° utilization factor Life in Years = : anade current in amperes 365 ad ° is) ° apo bh WHVBRBO0O ANODE SPACING M M M M 9 9909 us e) i) = fe) 7) S S = =e ro) ° ,e) fe) z ) 2 Se (o) = uw 3) z re 2) H Ww in 2) Figure 102. Chart of anode spacing (impressed current method). APPROX. INTERNAL ANODE RESISTANCE IN 300 OHM/CM BACKFILL 17 LB MAG ANODE: 0.96 OHM 1.5M LONG ANODE: 0.60 OHM — je) 17 LB PACKAGED MAGNESIUM ANODES AT 4.6 M SPACING pop 9 9 SSoC_o & AD YWH0O w 1.5 M LONG ZINC OR MAGNESIUM ANODES AT 4.6 M SPACING ie) wy) Sie O ~ = x ©) {e) ° 2 = 12) = x= (o) z uJ .S) z — = ie) wn WwW je 10 NO. OF ANODES Figure 103. Chart of anode spacing (galvanic anode method). 366 Table 57. Copper wire resistance. Resistance of standard copper wires in milliohms (ohms times 103) per meter at 25°C (77 F) Impressed Current Anode Installations = oo Oo oO & & © Hein ice nut ee Cie Gate Galyanic Anode Installation 2. 3 Substructure Test Stations Instrument Test Leads Temperature Correction Factors | Multiply Resistance at 25 C by: 0 52 é (b)) fox zane: anode weight P : 0.009 5 » in newtons - efficiency * utilization factor Life in Years = ————___——__—————— anade current in amperes (c) for aluminum (Galvalum II alloy) in seawater: anode weight A é : 0.035 ° in newtons - efficiency * utilization factor Life in Years = CIS eS ol ARICA aS ESS) Ca anode current in amperes 367 Using the values from Table 52 for theoretical ampere hours per newton and current efficiency, along with an 85 percent utilization factor for the three anode materials, the above expressions may be simplified to: 1.105 W Magnesium LS sacra eae Oe (4) Zinc he oe OFS (5) Aluminum I = £570 N sO : (6) where L is the anode life in years, W the anode weight in newtons, and I the anode current in amperes. As may be noted, Equations (4), (5), and (6) may also be used for calculating anode bed life where L is the anode bed life in years, W the total anode weight in newtons (all anodes), and I the anode bed current in amperes. (7) Deep-Well Anode Beds. Some mention should be made regarding deep-well anode beds, as in recent years they have attracted much interest for impressed current systems, primarily on pipelines. Such installations can be very useful if conditions permit. In the case of pipelines the well may be in the pipeline right of way, avoiding the requirement for additional right of way for conventional surface type anode beds. A deep-well anode bed, usually 60 to 120 meters (200 to 400 feet) in depth, can be ‘described as one in which the anodes are placed in remote earth by drilling straight down or by using an existing hole such as an abandoned water well. For pipelines this accomplishes the same general result obtained by locating a conventional surface type anode bed laterally several hundred feet from the pipeline. Advantages of a deep-well anode bed include small surface space needed (little or no additional right of way), probably less interference problems, and frequently lower anode-to-soil resistance than with conven- tional anodes. Disadvantages include great difficulty or impossibility of repair, necessity to prevent contamination of underground potable water sources, difficulty in determining soil resistivity at depths of several hundred feet, and expense of installation. (8) Application of Calculation Methods. With the preceding back- ground on design considerations, some examples follow to show how designs may be worked out for several types of subsurface structures. Professional consultation is advisable before finalizing plans for any cathodic pro- tection installation. Each location has specific problems which must be recognized and considered if the installation is to be effective and reasonably trouble free. c. Example Project. A part of the waterfront facility consists of a steel sheet-pile bulkhead (see Fig. 104 for cross section). It shows a typical seawater cross section, illustrating the various zones of exposure. The waterside of the bulkhead should be provided with cathodic protection as soon as possible to prevent further loss of steel caused by the corrosive action of the contacting seawater. Average water resistivity is 20 ohm- centimeters. The soil side of the bulkhead is also to be provided with cathodic protection at an early date. Average soil resistivity is 500 ohm- centimeters. A minimum of 20 years life for the waterfront facility is anticipated. f 368 ANODE HEADER CABLE eee, RECTIFIER> / WATER LINE TO ANODE RECTIFIER- WATER LINE To STRUCTURE CHANNEL BOTTOM Figure 104. Cross section of wharf used in example. (1) Conditions. The steel sheet-pile bulkhead is 300 meters (980 feet) in length. There are approximately 9 meters (30 feet) of water- exposed steel or 2 700 square meters (29 000 square feet) including a two- foot splash zone and about 3 000 square meters (32 300 square feet) embedded in the sandy clay soil. The steel surface contacting the water is expected to require about 55 milliamperes per square meter (5.1 milliamperes per square foot) for protection. The embedded part, 3 000 square meters is expected to require about 22 milliampere per square meter (2.0 milliamperes per square foot) for protection. (2) Calculations. Current requirement: 2 700 square meters @ 55 milliamps per square meter = 149 amperes. 3 000 square meters @ 22 milliamps per square meter 66 amperes. Total current required 215 amperes. (3) Resistance. Anodes used will be Durichlor 51 Type E, 7.6 centimeters (3 inches) in diameter, 1.5 meters (60 inches) long, to be suspended in the water under the wharf using polypropylene rope. These anodes are rated at 4 amperes per anode for long service life. 215 (amperes required) _ 54 anodes 4 (amperes per anode) 369 For safety margin use 60 anodes, spaced evenly under the wharf, about 5 meters (16 feet) apart. Using equation (3) the anode resistance of each component of the example project is calculated to determine the total anode resistence: 60 anodes, averaging 20 ohm-centimeters resistivity = 2 milliohms. Rectifier positive to center of header cable under wharf: 30 meters No. 4/0 copper cable in conduit = 5 milliohms Rectifier negative to bulkhead: 30 meters No. 4/0 copper cable in conduit 5 milliohms Header cable under wharf, center connection, effective length, 155 meters No. 1/0 51 milliohms Bulkhead resistance is negligible. Total resistance 63 milliohms (4) Voltage Requirement. Required rectifier voltage is obtained using Ohm's Law: E = IR or required voltage is equal to total current multiplied by total circuit resistance or E = 215 x 63 = 13 500 millivolts (13.5 volts). For best results, a current and voltage requirement test should be made after the anode installation is complete, including the cables to the rectifier location. A direct current welding generator capable of furnishing the above current and voltage should be used. For test purposes, complete polorization is not required. However, current should be applied for several days, with potential measurements made from bulkhead to a reference electrode in the water within 1.5 meters of the bulkhead (to minimize IR drop in the readings) at several locations and at several depths, from surface to bottom. Readings of -0.85 volt to a copper sulphate reference electrode or -0.84 volt to silver-silver chloride reference electrode indicate adequate protection. (5) General. Some comments should be made regarding the example. A continuous 25-millimeter-diameter steel rod should be welded in place in two locations to each sheet pile for the full length of the bulkhead. This con- nection rod should be well above the splash zone and should be well coated to ensure permanent connections. Woven grounding straps bolted to the sheet pile may also be used, if they are protected against the environment. The point must be made that the connections must be flexible. A sheet-pile bulkhead may deflect enough to break welds to a rigid 25-millimeter (1 inch) steel rod. Electrical continuity to each and every sheet pile is essential for the success of the cathodic protection system. Care should be taken to ensure that the steel bulkhead is electrically isolated (insulated) from all other structures or piping. Again, this is essential if the protected installation is to remain reasonably trouble fees 4. Cathodic Protection and Coatings in Combination. A combination of cathodic protection and coatings provides the advantages of both. Protective coatings are known to be the primary considerations 370 for protecting steel. Cathodic protection is needed as backup in areas where the continuity of the coating is affected, due to damage or applica- tion problems. If no coatings were used, the cost of cathadic protection would be greatly increased, both in terms of (1) equipment needed and (2) current required for protection of a bare (noncoated) structure. Examples of structures where cathodic protection is used in conjunction with coatings include: sheet piling, production platforms, piles, dacks, and similar structures continuously immersed in water. In these instances, the protective coating must possess: (a) Good dielectric strength, (b) good alkali resistance, (c) good adhesion characteristic, (d) low moisture absorbtion and transfer rates, (e) good coating thickness, and (f) resistance to the passage of ions. Carefully conducted tests and field use show that most coatings designed for immersion in seawater which have the properties described above will perform satisfactory at steel potentials ranging from -0.8 to -1.3 volts with respect to a copper/copper sulfate reference cell. Above the 1.3-volt potential many coatings will show degradation such as cathodic disbondment. If a good coating can be applied to both sides of the bulkhead pile sheets before installation, cathodic protection current requirements would be decreased drastically. The coating, if applied, should be as good as the state of the art permits, such as white metal sandblast, inorganic zinc primer, followed by two coats of coal-tar epoxy, for a dry film thickness of at least 0.41 millimeter (16 mils). In any event, the piling, after installation, should receive such a coating from the low water line upward through the splash zone to the top of the bulkhead. Any cathodic protection is marginal above the low water line and nonexistent in and above the high water line. 5. Marine Exposure. The characteristics of coating systems and structure material to be protected, as well as the specific marine exposure, will determine which coating systems can be effectively used. The specific marine exposures must be carefully considered when selecting a coating system to achieve good structure protection. Marine exposures are generally considered to be marine atmosphere, splash and spray zone and submerged zone. More than one of these exposures may occur on any single structure. For example, a marine atmosphere is one which carries airborne salt. Since only pure water evaporates from a body of saltwater, this physical process does not put salt into the air. Instead, salt becomes airborne only under conditions in which finely divided saltwater droplets (spray and Sal mists) are projected into the air by wind and waye action. These fine droplets may remain as such for some time, or the water may evaporate, leaving a tiny, solid particle of salt. Wind may carry the droplets or the salt particles some distance from the point of origin. [It will be seen, therefore, that the term marine atmosphere is not a precisely definable exposure condition. The term might be applied to any situation where the salt content of the air is great enough to exercise some effect on corro- sivity and on protective coating performance. The produced effects may range from very intense to near zero. The concentration of airborne salt, both close to the shoreline and at increasing distances from it, is difficult to even generally predict, since shoreline topography, wave heights, pre- vailing wind direction and velocity, and inland physical features are all important factors. However, the intensity of the corrosive effect declines rapidly as the distance from the shore is increased and in most cases, supposed acceleration of corrosion many miles inland is largely imaginary. It has been reported that the effect of marine spray is negligible at distances 3 kilometers (2 miles) inland and that analysis of iron corrosion products at seaside towns usually shows more sulfur (from industrial contamination) than chloride (from salt spray). There is no doubt, however, that steel surfaces subject to atmospheric exposures that are intensely marine in character present protection problems which are not solved by surface preparation and paint coatings customarily used for inland structures. The effects introduced by the salt are manifold and varied. An obvious effect is that the corrosion-accelerating influence of the salt causes even the smallest discontinuity and thin spot in the coating to become a focal point for rusting which rapidly enlarges the original corrosion site. This effect is heightened by the fact that the corrosion products (rust) formed in salt-bearing atmospheres do not exert a protective influence against further corrosion to the degree that they do in inland locations; i.e., corrosion continues at a high level in marine atmospheres, whereas the rate usually drops off considerably in most inland atmospheres. The electrochemical reactions involved in the salt- accelerated corrosion processes result in alkalies and other products which may be both harmful to the paint film itself and to adhesion of the coating to the metal. The net effect of the presence of even small amounts of deposited salt is to increase the need for more care in surface preparation and paint application; in more severe cases, it brings about a need for a more re- sistant coating system than is customarily used on inland, weather-exposed steel. The need for thoroughness in surface preparation and paint applica- tion cannot be overemphasized. This need is increased by the fact that crevices, joints, junctions of joining members, interior angles, pockets, undersides of horizontal and inclined members, and similar surfaces tending to be protected from the direct action of rain which would wash away the salt, are the places of greatest corrosion and are also the places which tend to receive the poorest paint job. Structures exposed to moderate and moderately severe marine atmospheres should receive a more advanced paint system. Thorough inspection is probably at least as important as the proper choice of coating. 6. Uses in Coastal Structures. Generally the generic coating systems discussed in this section have found satisfactory use in the exposures shown in Table 58. 3f2 Table 58. Typical uses of coatings. Alkyds On metals in mild marine atmos- phere. Silicone Alkyds On metals in mild marine atmosphere. Acrylic (Solvent based) Qn metals in moderately severe marine atmosphere. Acrylic (Water Reducables) On masonry, concrete and wood in moderately severe marine atmosphere. Chlorinated Rubber On metals in splash and submerged zones. Coal Tar a. Mastics and Coal-Tar Splash and submerged zones. Cutbacks b. Modified Coal Tar Splash and submerged zone. Epoxies (Catalyzed) Splash and submerged zone; has ex- cellent toughness. Epoxies - Phenolic Splash and submerged zone but is brittle. Phenolics Heat cured; high corrosion resis- tance but brittle; used for tank linings. Polyurethanes (or Urethanes) Usually heat cured; splash and submerged zone; tough with high abrasion resistance. Vinyls Marine atmosphere, splash and sub- merged zones; poor solvent resistance. Zine (Inorganic) Splash and submerged zone; used as single or multiple coat system. Zine (Organic) Splash and submerged zone; generally the higher the zinc content the better the coating. Underwater Coatings and Good for in place structures in sub- Mastics merged structure. 373 XII. SUMMARY 1. General. This section summarizes the principal properties and uses of materials in coastal structures, beach protection devices, and erosion control. Generally more than one material is used in a single coastal structure and compat- ibility and effectiveness of the materials working together must be con- sidered in each case. The selection of materials for a specific coastal structure may require consideration of the cost of labor and availability in addition to the physical properties of the materials. Such considerations influence the design of structures when more than one material can be em- ployed to perform the same job.. By considering the properties of materials and their past performance experience, the coastal engineer may select the proper material to achieve his design objective. Material uses are generally considered first for their structural properties and then their durability in coastal structures. In addition to the detailed information given in the preceding sections, the general summary that follows may assist in the selection of materials. Most, if not all, of the common construction materials have been used separately or in combinations of two or more in the creation of coastal structures. For example, breakwaters, both detached and shore-connected, are commonly constructed of earth and stone and in many instances capped with concrete armor units. To the commonly used earth and stone, steel and concrete sheet piles have been added from time to time for special functions. Also, asphalt has been used many times as an earth and rock binder for capping such structures and holding the basic materials in place. Bulkheads and retaining walls have been constructed of stone, sheet piles made of concrete or steel, mass concrete, and wood. Groins and jetties have been built of these materials as well. Marine and harbor structures of more complex design usually require the use of a variety of materials in construction, the selection based not only on their physical properties but their availability at the site and ease of installation as well as economy of construction. When temporary structures are called for, recycled materials such as broken or crushed concrete, crushed asphalt concrete, blocks and salvaged or scrap metals (such as ships, barges, and railroad cars) have been used. The recent development of a large variety of synthetic materials has resulted in the production of improved coating systems and synthetic films for filter cloths as well as foams for improved buoyancy. The synthetic rubbers are used as energy absorbers in fender piles, bumpers and other protective devices. Many materials, when used in coastal structures, require special treat- ment. Wood, for example, will have a substantially improved service life when properly pretreated with creosote and other preservatives. Metals, and more specifically steel, will require protective coatings or cathodic protec- tion (usually both) to be durable in the coastal environment. 2. Materials. a. Stone. (1) Properties. Stone refers to individual blocks, masses, or fragments that have been broken or quarried from bedrock exposures,' or are 374 obtained from boulders and cobbles in alluvium. Crushed or broken stone includes all stone in which the shape is nat specified. Stone for coastal structures should he free from laminations, weak cleavages and be of such a character that it will not disintegrate from the action of air, seawater,or handling and placing. A stone of high specific gravity is desirable because it increases the resistance to movement by the action of waves or currents. Durability of stone can be affected by its mineral composition, texture, structure, hardness, toughness and resistance to the effects of wetting and drying and freezing and thawing. Stone is generally classified as granite, basalt and related rocks, limestone and marble, sandstone and miscellaneous stone. While no standard testing procedure has yet been developed for the determination of the quality of stone, other than past experience with specific quarries, there are testing programs that are used. With any testing program for the determination of the quality of rock, judgment is necessary in applying and interpretating test results. This requires a great deal of experience and should be left to geotechnical experts. Any test program should include petrographic examination, determination of absorption and bulk specific gravity (ASTM Standard C97-47 or C127-77), a soundness test (AASHTO T-104-46 or ASTM C88-76) and an abrasion test (Los Angeles rattler, Wetshot rattler or ASTM 535-69 {75}). Other tests may prove useful depending on specific project requirements. Properties contributing to durability of stone may be both physical and chemical and chemical changes can best be evaluated by experts. (2) Stone Size and Shape. Stone size is important in coastal structures. Bedding layer material, core rock or quarry-run material is usually 15 to 20 centimeters (6 to 8 inches) or less. Underlayer stone may range from a few kilonewtons to about 30 kilonewtons. Armor stone is the largest size and ranges up to 220 kilonewtons. Stones larger than about 220 kilonewtons are generally not easily handled. While the three ranges of stone sizes are required for the different parts of a rubble-mound structure, an adequate number of classes within each range is also necessary. In fitting stones into a structure, the shape as well as the size is important. Design requirements usually specify that the greatest dimension of an indi- vidual stone be no more than three times its least dimension. In addition to the physical properties of stone, the method of quarrying will also determine the size, range and classes within a size range that are produced. Depending on the area topography, a quarry will generally be developed as either a side hill or a pit-type operation. The size of quarry face developed in any given operation is usually determined by the thickness of the formation. The method of blasting and the type of explosive, as well as the geological and physical characteristics of the material, will determine the degree of fragmentation that will result from the quarry operation. Generally a high powder factor (quantity of explosive per unit volume of rock) will produce a greater degree of fragmentation than will a lower powder factor. Also, greater fragmentation will be achieved in a massive rock by using a large number of small diameter holes at close spacing than by using large diameter holes at greater spacing. It also appears that best fragmenta- tion is achieved when holes are detonated individually rather than simulta- neously. 375 (3) Use in Coastal Structures. Stone has many uses in coastal structures, including offshore structures, shore-connected structures, and anchors. Breakwater, jetty and groin design often include several sizes of stone for use in the core and underlayers and for use in the covering or armor layer. Seawalls and revetments may also be constructed from stone. For protection of pier foundations a quarrystone blanket may be laid under the pier in the scour area. b. Earth. (1) Properties. Earth or soil is a large assortment of materials of various origins. For engineering purposes soils are generally classified as gravel, sand, silt, clay,and organic material; however, most soils are composed of a mixture of two or more of these materials. Although there are several soil classification systems, the most widely used in engineering is the Unified Soils Classification System (USCS). Gravel is usually considered to range in size from the No. 4 Sieve to 76.2 millimeters (3 inches). Gravels are cohesionless materials. Sand is defined as a grain size between 4.76 millimeters and 0.075 millimeter (No. 4 and 200 sieves, respectively) and sands may be further classified as coarse, medium, or fine. Sands are normally cohesionless materials; however, they present an apparent cohesion when damp or moist due to the surface tension effects of pore fluids. Silts and clays are known as fine-grain materials. Silts may also have an apparent cohesion but have relatively poor strength characteristics, limiting their use to certain cases. Clay materials are largely cohesive, have strength characteristics dependent on past stress history, and may be difficult to compact at high moisture contents. Minerals included in the clay composition influence the properties of the soil. Organic materials, formed by the decay of vegetable matter can be entrained in soils and usually have a spongy nature and a fibrous texture. Usually organic soils have high moisture and gas contents and a relatively low specific gravity. The major significant engineering properties of soil are shear strength, compressibility, and permeability. The types of problems encountered in the design of coastal structures which utilize these characteristics are slope stability, bearing capacity, settlement, and erosion. Other useful properties of soils in the design of structures include dry density, water content, specific gravity, resistivity and corrosion potential, grain-size distribu- tion, plasticity characteristics, chemical properties, and durability. (2) Soil Placement Methods. Soil placement methods are usually determined by the fill location, underwater or above water, and the need for some degree of compaction. Earthfills made from land are usually truck- dumped and bulldozed into place while waterside delivery may be by barge or hydraulic pumping. Fill compaction above the water can be accomplished using mechanical equipment. A fill placed under water will usually require some form of superimposed loading for a period of time to compact it. This loading time depends upon the depth of fill and amount of loading. It usually varies from 0.5 to 2 years. The compactibility of the soil will also impact the loading time. (3) Use in Coastal Structures. Earth is commonly used in virtually any port or harbor development, land reclamation, or coastal protection structure. In addition to fill of all kinds, earth is used in making soil- cement as well as fill material for plastic bags and other containing units. 376 c. Portland Cement Concrete. (1) General. Concrete is used as unreinforced or mass concrete, as steel reinforced concreté or as prestressed or posttensioned concrete. The latter types are usually made in the form of precast structural elements. Specific properties of concrete may be modified and improved by the addition of admixtures for special purposes and to accommodate placing and installa- tion requirements. The specific use of concrete in any structure will determine the mix design and curing process necessary to obtain a satis- factory result. Experience or consultation with experienced designers of concrete structures is necessary to ensure a durable concrete appropriate to the needs of the structure. Durability is generally a requirement in coastal structures and the designer and constructor share the responsibility for creating structures which will function as designed over the anticipated life of the structure. Such structures have a high resistance to the disruptive attack of most environments including saltwater, alkalis, most acids, corrosive atmospheres, freeze-thaw cycles, and marine flora and fauna. Good concrete is also highly resistant to abrasion. Failures of concrete structures have been studied and some of the more common causes of failure and methods of prevention are discussed in Section V. Determination of the cause of structural failure requires a careful analysis of the site conditions, the concrete ingredients, and the original design criteria by experienced professional engineers. Concrete failures usually are the result of the selection of the wrong type of cement, unsound aggregate, contaminated mixing water, improper admixtures or an inadequate curing process. With all these possibilities for creating poor concrete the design engineer must also have experience and good judgment in preparing plans and specifications to ensure that concrete is used within its physical capabilities. (2) Uses in Coastal Structures. Thousands of marine structures have been satisfactorily designed and constructed of concrete with a long history of excellent performance. Because the resources required to make good con- crete are generally available in all regions of the world, concrete has wide application for use in coastal and waterfront structures. Its successful use in seawalls, bulkheads, revetments, groins, jetties, breakwaters, and a variety of other structures over many years is evidence of its excellent properties for coastal engineering use. d. Other Types of Concrete and Grout. (1) Asphalt. (a) General. Asphalt is a residue product from the refining of petroleum. It can be used alone as a membrane or coating or it can be mixed with other materials as a binder to produce mixes for a variety of purposes. Asphalt can be combined with sand and graded aggregate to form a voidless and impermeable asphalt concrete or with an open-graded aggregate to form a stable porous mixture. A composite asphalt structure can easily be con- structed of different asphalt mixes with each layer performing a particular function. An example of this use might be an impermeable asphalt layer 377 supported by an open-graded asphalt drainage layer with an asphalt mastic placed with a screed over the compacted subsurface. The drainage layer serves to prevent damage to the watertight outer layer by draining away any seepage through the outer layer or any ground water intrusion. The physical properties of asphalt alone are considered in its use in coastal structures in addition to its adhesive properties as a binder and its viscous properties under service conditions. The manner of asphalt placement as well as the service conditions will require certain minimum and maximum viscosities. (b) Use in Coastal Structures. Engineers have made consider- able use of asphaltic materials in the construction of many structures for coastal protection. Asphalt concrete is used to pave or revet the slopes and tops of earth or sand seawalls. It may also be used to pave, or cap, the top surfaces of quarrystone jetties, breakwaters, groins, and cellular steel breakwaters. Asphalt mastic mixtures are also used for grouting to fill-in the voids of quarry stone jetties and groins, and of the riprap facings of seawalls and revetted slopes. In foreign countries special equipment has been designed to place a sand-asphalt mastic under water in a continuous operation. The blanket is designed to prevent scour of large areas of the seabed. As more and more emphasis is placed on pollution control, engineers are finding that asphalt offers an economical and effective means of lining dredge disposal sites and waste storage areas that are sometimes necessary in the construction of coastal structures. Asphalt has an excellent history of performance in its use in coastal structures when properly designed and used in accordance with its physical properties and capabilities. (2) Preplaced Aggregate and Grout. Portland cement grout poured in the voids of preplaced aggregate is a specialized construction method. It generally uses large stone with the voids filled with grout. It is a type of mass concrete used as a seawall or bulkhead. The physical properties as to durability, resistance to abrasion etc. are much the same as those of the stone and concrete components. One difference is in the cement grout mix design. Pozzolons and fluidizers are added to improve handling during placement and bonding to rock or old concrete. (3) Portland Cement Grout. Portland cement grout will have the same physical properties as Portland cement concrete of similar mix design. Grout, however, is usually modified in its mix design because of its intended use and placement methods. This results usually in a grout mix of cement and water with sand. Very small gravel and clay, used as inert fillers, or even bentonite used as a stabilizer, may be added when it is placed under water. Grout is easily placed by pouring, pumping or injecting into place. In filling joints or narrow cracks it can usually be poured into place. In filling large voids or holes, pumping is a common procedure. When stabilizing ground beds for foundations or the area behind bulkheads to prevent leaching of the soil it may be injected into the ground or structure. This injection procedure may be the same as pumping but at relatively high pressure. (4) Soil Cement. Soil cement is a mixture of pulverized soil and measured amounts of Portland cement and water compacted to a high density. The physical properties of soil cement are its high density as compared to uncemented soil and its rigidity, resulting in a structural slablike material 378 with the use of small quantities of cement. In good soils, 7-day compressive strengths of 2 070 kilopascals (300 pounds per square inch) are obtainable. Soil cement is used primarily as a base course for stabilizing and compacting soils for foundations, bank protection, and subbase construction. It has been used for earth dam cores, reservoir linings, and slope protection. (5) Sulfur Cement. Sulfur cement concrete and grouts are a rela- tively recent development and as such do not have a long history of use in coastal structures. Recently, the availability of large quantities of sulfur has resulted in its increased use in construction projects as a binder or admixture of aggregates. Molten sulfur mixed with sand and aggregates pro- duces a sulfur concrete of excellent strength. Sulfur-asphalt binder materials have higher densities than normal asphalt as sulfur is about twice as heavy as asphalt. The sulfur-asphalt binder usually results in a lower void percentage than the asphalt cement without the sulfur addition. Sulfur does increase resistance to gasoline, diesel fuel, and similar solvents. It also improves stress fatigue characteristics. The finely dispersed sulfur particles add strength to impregnated fabrics. Whereas sulfur cement materials reach their full strength quickly upon cooling, the inherent flammability and low melting point of sulfur impose some limitations on the use of sulfur cement. However, because of its quick-set characteristics, it may find many uses in emergency repairs that could have considerable longevity. With more experience and additional development, sulfur-cement products will probably find increased use in coastal construction. e. Structural and Sheet Metals. (1) Steel. Steel is the most utilized of all metals in marine service and for coastal structures. Carbon steel is an alloy of iron and carbon in which the carbon content is less than 2 percent. Structural steel limits the carbon content to less than 0.35 percent. Adding small amounts of alloying elements during the steelmaking process can improve the mechanical properties of steel as well as its corrosion resistance. Small additions of copper, nickel, chromium, silicon,and phosphorus have been effective in improving the corrosion resistance of steel. In addition to its strength, the mechanical properties of steel of most interest in the design of steel structures are: ductility, brittleness, malleability, flexibility, hardness, resilience and toughness. Ductility is defined as the ability of a material to be drawn out without change in volume. Brittleness defines its lack of ability to be deformed without rupture. Malleability is the opposite of brittleness and refers to its ability to be forged or rolled into thin sheets. Flexibility describes its ability to bend under stress and return to its original shape when the load is removed. Hardness is a measure of its ability. to resist indentation when subjected to impact. Resilience is its ability to absorb energy due to applied loads without breaking. Toughness indicates its ability to absorb large amounts of energy without rupture. Structural steel has a high degree of all these properties. ‘ 379 It is relatively easy to alloy other metals with iron in making steel. Low alloy steels contain up to 1.5 percent of elements such as manganese and silicon. Medium alloy steels contain 1.5 to 11 percent of alloy elements and high alloy steels, including both ferritic and austentic stainless steels, contain more than 11 percent of alloy elements. Most coastal structures using steel as a principal construction material use certain steel shapes in the following manner: (a) sheet piles for caisson walls, cutoff walls, bulkheads, and groins; (b) "H' sections for bearing piles and beams; (c) pipe or tubing for bearing piles, conduits and handrails; (d) solid rods for tiebacks or tension members; and (e) reinforcing bars for concrete. (2) Aluminum, Aluminum, being a light metal in its high purity form, is soft and ductile but does not possess sufficient strength for structural applications. The addition of alloying elements imparts strength to the metal. Elements used as alloys in aluminum are copper, magnesium, zinc, silicon and small amounts of other elements such as chromium, usually with copper to obtain high strength structural shapes. (3) Copper. Copper has several unique properties that make it a very useful material. In addition to its high thermal and electrical con- ductivity it has high corrosion resistance and can improve other elements by being readily alloyable. The most corrosion resistant of the copper alloys to seawater are aluminum brass, inhibited admiralty brass, and the copper- nickel alloys. (4) Use in Coastal Structures. Steel is used as structural shapes in most types of coastal structure, It is used as well in composite struc- tures, for example as rebar in concrete construction. Steel alloys have found many uses as bar stock, wire and wire fabric. Many alloys of aluminun, due to their high corrosion resistance as well as strength-to-weight ratios have also found many applications in marine structures. Copper, in addition to uses as pipe and sheathing, has a high alloying capability in bronze and brass that makes it a very useful element in the marine environment. In the use of steel, alloys and other metals in the coastal environment, care must be taken to avoid direct contact of dissimilar metals that can form a galvanic couple. When dissimilar metals are in electrical contact with each other and immersed in an electrolyte, a potential difference is estab- lished; an electric current will flow and rapid corrosion will take place. If two dissimilar metals must be joined, then several precautions must be taken such as insulating the metals, avoiding unfavorable effects by keeping the cathode area small, placing a more anodic third metal in contact with the other two to provide sacrificial protection and invest eae other possible solutions to protect the structure. 380 f. Wood. (1) General. As a construction material, wood is available almost everywhere and at reasonable cost. It is a cellular organic material made up principally of cellulose, which comprises the structural units, and lignin, which cements the structural units together. A tree has distinct zones: bark, sapwood, heartwood, and the pith at the center. There is no consistent difference between the weight and strength properties of heartwood and sap- wood. Because wood is produced by nature under various uncontrolled environ- mental conditions, such as geographical location, precipitation, exposure, and elevation, the product is highly variable. Also, trees are alive, producing wood of different properties at different ages. For a given characteristic or property of wood, such as its bending strength, both the mean value and its variation encountered about the mean should be considered. Lumber grading rules are, in effect, specifications of quality. The size and number of knots, slope of grain and other strength reducing character- istics are judged and graded according to uniform standards so that working stresses can be assigned to specified quality. Common construction species generally available in the United States are Douglas fir, southern pine, spruce, hemlock, redwood, cedar and other pine species such as lodgepole, ponderosa and white. (2) Properties. The major mechanical properties of wood as they affect engineering design are: (a) Tension Parallel to Grain. Tension parallel to grain creates a tendency to elongate wood fibers and cause them to slip by each other. Resistance to tension applied strictly parallel to the grain is wood's highest strength property, but if tension is applied at an angle to the grain or the cross section of the piece is reduced by knots or holes this strength may be materially reduced. (b) Tension Perpendicular to Grain. Tension perpendicular to grain tends to separate the wood fibers along the grain and is the direction in which wood has the least strength. (c) Compression Parallel to Grain. Compression parallel to grain creates a tendency to shorten the wood fibers in the . lengthwise direction. Resistance of wood to this force is good but is affected by the angle of the load to grain and by the presence of knots and holes. (d) Compression Perpendicular to Grain. Compression perpendicular to grain, such as the bearing under the ends of a beam or under a column, tends to compress the wood fibers together. The wood becomes more dense and the action may cause slight displacement at the bearing face. (e) Shear Parallel to the Grain. The largest stress usually occurs along the neutral axis of a beam. During the drying of lumber, checks and splits may occur reducing the area in the plane of maximum shear; therefore the shear strength for design is reduced to accommodate this probability. t 381 (f) Shear Perpendicular to Grain. Shear perpendicular to grain is not a design factor as effective control is applied through limits on design stress for shear parallel to grain. (g) Fiber Stress in Bending. Fiber stress in bending creates compression in fibers on one side and tension in fibers on the other side of a beam. The higher stresses occur in the fibers most distant from the center. Deviations in the slope of grain and the presence of knots and holes in these outside faces reduces the resistance in the extreme fibers. (3) Preservative Treatment. In order to extend the useful life of wood long enough to make it an economical and practical material for use in the coastal zone or other marine environments, it must be protected from its natural enemies, fungi, bacteria, insects and marine organisms. The most effective method of treating wood with preservatives is the pressure-treating process. The pressure-treating process requires placing the wood in an air- tight chamber in which either a vacuum or a pressure can be created while the preservative is introduced into the chamber. The preservative generally will penetrate the wood surface from 1.5 to 4 centimeters (0.5 to 1.5 inches) and coat the walls of the wood cells in this area. Penetration to 10 centimeters (4 inches) is required in some cases. Although two processes, the empty-cell and the full-cell process, have had success in preserving wood structures in marine environment, the full-cell process is most commonly accepted as the preferred treatment for coastal zone use. Wood preservatives commonly used are grouped into two broad classes, preservative oils and waterborne preservatives. The preservative oils are considered the best wood protection in a marine environment and include byproducts of petroleum such as creosotes, coal-tar creosotes, and mixtures of these with other oils. They may include solutions of toxic chemicals such as pentachlorophenol or copper naphthenate. Waterborne preservatives include solutions of chromated zinc chloride, fluor-chrome-arsenate-phenol, chromated copper arsenate, and other toxic chemicals. (4) Other Protective Methods. In a marine environment wood struc- tures can be protected by other materials which are not strictly preserva- tives. Such protection is in the form of sheet metal, concrete jackets and flexible synthetic sheets such as vinyl and polyethelene films. Because virtually all organisms causing wood deterioration are aerobic, surrounding a wood element such as a pile with a jacket that prevents seawater containing free oxygen from coming in contact with the wood creates a hostile environ- ment for the organisms. (5) Durability. Wood, when properly treated with appropriate preservatives has a good history of satisfactory service in marine and coastal structures. Wood piles supporting piers and wharves, when not subjected to abrasion, have lasted many years. Wood sheet piles in groins, jetties, bulkheads and like structures will perform satisfactory. Care must be used in installing wood members to ensure that construction joints and connections do not damage the preservative protection or ienene field repairs are carefully and adequately made. 382 Chases (1) General. Chemically the term "plastics" is applied to a large group of synthetic materials, including synthetic rubber, that are processed by molding or forming into final shape. Plastics that are soft and pliable at some stage in their production are formed into shape by the application of heat and pressure. They are organic compounds that are transformed into complex synthetic materials by chemical processes. They are high polymers in that they consist of monomer atoms joined together into molecular aggrega- tions called polymers. Plastics in general may be classified into two distinct groups, thermo- plastics and thermosetting plastics. Thermoplastics soften repeatedly when heated and harden when cooled. Thermosetting plastics go through a soft stage only once. When hardened, an irreversible change takes place and they cannot be softened again. Plastics can also be combined for a particular end use, drawing together the best attributes of the blended components by copolymerziation. The products are called copolymers. During the production of plastics, additives such as plasticizers, fillers, colorants, stabilizers and impact modifiers can be added. In addition to structural qualities, plastics are easily formable, corrosion resistant, lightweight, wear resistant, energy absorbant, impact resistant, flexible and ductile. A necessary consideration in the use of plastics is that plastics will burn, some easily, others slowly and others with great difficulty. (2) Geotextiles. Plastics in the form of geotextiles have an important use in coastal structures, commonly functioning as filters in drainage, shore and embankment protection structures. Geotextiles are a relatively new material in the construction industry but have had a generally successful experience record as filters in selected coastal structures over the past 20 years. Substantial improvement in the design and materials selection specifications has also occurred. The primary function of geotextiles when used as filters is to retain the protected soil (prevent piping) and remain permeable to water without sig- nificant head loss or the development of excessive hydrostatic pressure. To function satisfactorily, the geotextile filter must have physical durability and filtering integrity throughout the design life of the structure. In the selection of a geotextile for a filter, the chosen fabric, in addition to having required physical and chemical properties, should be of a kind and finished form consistent with the site-specific requirements. Fabric construction is a predominant factor affecting performance. Woven fabrics are commonly manufactured by crossing the yarns at right angles, overlapping one over the other, the yarns being monofilament, multifilament, mono-multifament or slit-film. Nonwoven fabrics include all materials not woven or knitted. They consist of discrete fibers, which may be random or pattern oriented in the fabric. The bonding methods described are needle punched, heat bonded, resin bonded, and combination bonded. Combination fabrics are produced by combining woven and nonwoven fabrics by one or more bonding methods. : 383 (3) Use in Coastal Structures. Because geotextiles are relatively new as a construction material, there has not been sufficient time to develop agreed upon standard testing techniques for the most important characteristics a fabric should have for specific applications. However, they are finding many uses in coastal structures. Different fabric specifications may be required for specific uses, such as replacement of stone filters under riprap, drainage control by silt retention fabrics, and road stabilization by road or highway fabrics. Fabric users should seek the advice and recommendations of knowledgeable sources with experience in the specific use being considered, such as consultants and more than one manufacturer. Many forms of plastics other than geotextiles are also used in coastal structures. Flexible plastics are used as mold forms for concrete and for wrapping timber pile to provide protection from marine animals and for wrap- ping metal piles to prevent corrosion. Molded forms have applications as rubbing strips, fenders and bumpers. Plastic extrusions in the form of pipe and culverts are in common use. Pipe may be reinforced or not depending on the structural strength required. h. Recycled and Other Materials. Generally recycled materials consist of a variety of materials that may be available in a given location and are normally used in emergency situations as temporary (occasionally as perma- nent) protective devices against damaging waves or currents. Such materials should have a specific gravity greater than 1.5 to be useful unless a float- ing type of structure is needed. Materials considered in this category are salvaged concrete, concrete rubble, crushed concrete, recycled asphalt used either as rubble or crushed, blocks and bricks, and salvaged steel structures. Normally, because of the emergency type use of recycled materials, little consideration is given to the properties of such materials other than their specific gravity. Also, little concern is given to their environmental impacts; however, these im- pacts would generally be different than for the materials before recycling or reuse. Recycled or salvaged materials have been used for many years for emergen- cy repairs or to construct temporary structures. In many cases these tempo- rary structures have remained in place for many years. Salvaged concrete, either as rubble, crushed or unbroken has been used to repair revetments, groins, jetties and breakwaters. These materials may not have a pleasing esthetic appearance, especially if they contain reinforcing steel. If located in a recreation area, the reinforcing steel may create a safety hazard. Of course, exposed reinforcing bars will corrode at a rapid rate causing accelerated concrete spalling and deterioration. Generally these materials are used as a substitute for stone in coastal structures. Recycled asphalt can be used as an underlayer in coastal structures. Although it is relatively hard and unflexible because of its age, it will retain its broken shape for extended periods of time and further deteriora- tion is not a problem. Recovered asphalt may be crushed and used as core or bedding material in coastal structures, but unless well graded, it does not make a satisfactory filter material. Crushed asphalt is also finding greater use as a base material for highways, roads, streets, and parking lots. 384 Bricks, hollow concrete blocks, and cinder blocks have been used as temporary repair materials; however, they generally break down during han- dling and are nat of much long-term value. Also they have no value as an underlayer or armor layer. Salvaged ships and barges have been used as temporary breakwaters by manuevering them into a selected location, sinking them and then filling them with rock or gravel to provide stability. Removing these devices when a permanent structure is desired or upon their disintegration, is usually a difficult problem. Other salvaged materials such as railroad cars and auto- mobile bodies have been used in bank or shore protection, however, they are not satisfactory and are usually unsightly and hazardous if located where people may visit. Used rubber tires have a variety of uses such as fenders on barges, work boats and docks. They have also been successful as floating breakwaters to protect basins against short-period waves. Several different arrangements have been model tested. Flotation has been created by filling tires with urethane foam. If anchored in place or on the bottom, tires have served as a revetment and to slow the bed movement of littoral drift. i. Protective Systems. (1) General. Protective systems are applicable to steel and alloys; wood, and concrete, usually for esthetic reasons or, in some few cases, to decrease water penetration into relatively porous concrete. Protective systems are classified in two categories; coating and cathodic protection. Each of these systems may be used separately, but in many instances cathodic protection can be successfully used to supplement coating systems. (2) Coatings. Protective coatings range from mere decorative paints to complex and multicoat systems requiring careful surface prepara- tion, proper coating application techniques, and the careful selection of coating systems. In the consideration of a coating requirement, the first step is to consider the type and kind of surface to be protected, i.e., wood, concrete, steel or other metals and alloys. Next consider the environ- ment the structure surface is exposed to, such as a marine atmosphere, a tide or splash zone or a submerged zone in either fresh or salt water. With this information and other specific data as set forth in Section XI, the coastal engineer may then consider the generic category as well as the specific type of coating within a category that is best suited for the protection of a given structure. The types of coatings and their generic classifications are discussed in Section XI. To adequately evaluate a coating's protection performance it is necessary to consider the properties of the coating material, the surface preparation requirements, and the application procedure as well as the drying or curing processes. To aid evaluation, Section XI discusses the surface preparation processes including resulting metal surface anchor patterns, the number of coats and thickness, and the drying or curing pro- cesses necessary to obtain a good coating system that can be expected to properly protect a structure. Coatings are applied by brush, roller, spray (both air and airless), and dipping. Coating repair is a common procedure; however, there are precautions that must be taken to ensure successful repair. Coating compatibility is a must 385 to provide good bonding of the repair coating or to prevent any of the normal types of coating failures. Coating failures may be identified by the presence of blistering, undercutting, surfacing cracking, delamination, alligatoring, or chalking. Coating must have strength, adhesion, resistance to the environment and, many times, a pleasing appearance to properly func- tion. (3) Cathodic Protection. Cathodic protection is an electrical process to protect metal structures in an electrolyte. The electrolyte may vary from seawater to freshwater, saturated soil and even relatively dry soils. Disolved ions of acids or alkali salts tend to promote metal deterior- ation which can occur in localized areas or over large general areas of a metal surface. Metal corrosion is a natural process involving electrochemical reactions with a resulting flow of direct current from the anodic areas (the corroding areas) to the cathodic areas of the structure through the surround- ing electrolyte due to the electrical potential difference between the two types of areas. Cathodic protection is the process of inducing an outside electric current in the opposite direction and in this manner stopping the normal corrosion process. The design and installation of a cathodic protection system is highly technical. To ensure design of an effectively operating system, field conditions of the structure must be examined to determine the total amount of electrical current required to cathodically protect the structure and to ensure proper current distribution. It must also be determined that there will be no interference with other structures in the vicinity and that potential differences within either the protected structure or of adjacent structures are not impacted to ensure that no cathodic protection inter- ference conditions exist. Cathodic protection requires periodic maintenance and inspection to keep it in good working order. Generally good protective systems, both coatings and cathodic protection, are economical, require maintenance, and will substantially extend the service life of well-constructed structures. 3. Some Present Investigations of Coastal Construction Materials. a. Stone. Stone is one of the most widely used materials in coastal structures and shore protection works. There are two basic areas of research on stone: the uses of stone in shore protection structures and the character- istics of stone for use in coastal structures. Stone is used in revetments, jetties, groins, bulkheads, seawalls, and other miscellaneous types of structures. Studies are being done on new types of shore protection structures such as semisubmerged offshore structures, on new structure configurations for jetties, on different distributions or arrays of stone in armor units or layers, on the reliability of breakwater model tests, and on the effect of breakwaters on waves. Programs have been initiated to monitor and evaluate the performance of existing coastal struc- tures in terms of their effectiveness, maintenance cost and life. This area of research also deals with development of field techniques and criteria for the functional and structural design of coastal structures. Work is also continuing on the evaluation of parameters used for determining the effective 386 elevation of structures, the slopes of revetments to reduce runup, and the size of armor stone to dissipate energy. The use of stone in coastal structures is based primarily on experience. Continued research is needed on the development of testing procedures, criteria, and methods of quarrying to determine and produce rock character- istics that are desirable and suitable for use in coastal structures. Current research includes various tests for shrink and swell behavior, wetting and drying effects, mineralogic composition, specific gravity, and other physical and chemical properties. b. Earth. Current investigations and studies relating to the use of earth materials in the coastal and marine environment deal primarily with the behavior of soils under various nearshore conditions and their use in connec- tion with coastal structures. These investigations include numerous programs that are in progress to develop field techniques and criteria for use in design, construction, and maintenance of effective beach and dune protection. The programs seek to describe and predict the interactions between the materials that make up the coasts and the forces that act upon them. Studies include the development of mathematical models that designers can use to determine how much sandfill is required to adequately protect a segment of shore for a certain timespan and how often additional fill will be required. Studies are in progress to determine the effective use of earth materials in low-cost shore protection. New dredge disposal techniques are being studied to aid in beach nourishment projects and sand bypassing across coastal inlets. Several field research facilities and projects have been established to study coastal processes and their long-term effects on the erosion of and protection of the natural coastline materials. Research is also continuing on the engineering properties of the various soils. These studies include the determination of density and porosity of sea floor sediments, the grain-size distribution of beach materials, and the shear strength and consolidation characteristics of estuarine deposits. c. Portland Cement Concrete. Concrete structures are being increasingly utilized for a wide variety of applications in the marine environment. Structures are becoming more sophisticated and are being located in areas of more severe exposure (e.g., ice and open sea), and subjected to cyclic and impact loads. Consequently, their performance requirements become increas- ingly severe and critical. Investigations are being performed relating to internal response of structural elements, environmental conditions in which the structure must serve, new materials and configurations, construction practices and repairs, and new uses in the ocean. Existing problems relating to concrete design include cracking, spalling, and corrosion of reinforcing steel, as well as the purposeful overdesign and over-reinforcement of structures in an effort to cover the range of uncer- tainty. These problems indicate the need for additional investigation to better understand the properties of concrete. Investigations include: (1) Corrosion of reinforcement in submerged structures with varying widths of cracks. Also where cracks are repeatedly opened and closed under a large number of cycles there appear to be an 387 accelerated degradation which may be due to hydraulic fracturing of the concrete by entrapped water. (2) Placement of mass underwater concrete is being tested. Tremie concrete mixes and placement procedures are being investigated at the University of California and mass concrete placement in the deep ocean is being tested by U.S. Naval Civil Engineering Laboratory at Hueneme. Also, investigation of thixotropic admixtures to prevent segregation of concrete when flowing through water is being con- sidered. (3) Failure of dolos units and other armor units indicates the need for additional investigation to find more stable shapes, or the possible need for reinforcement to tie the member internally and improve its flexural strength. Repairs to precast concrete units of this kind, as well as other concrete structures have been carried out using epoxy injection. Continued tests on repaired units are needed to determine fatigue and ultimate strength as well as to gain a better understanding of the impact on other properties of concrete. | d. Other Types of Concrete and Grout. (1) Bituminous Concrete. Asphalt is made from crude oil and re- fineries in recent years are using crude from many different sources, making the characteristics of presently produced asphalts different from those previously produced. This results in problems in the handling and placing of asphalt cement and in its performance. Asphalt-related problems generally divide into two categories: workability problems and performance problems. Workability problems, which make asphalt more difficult to mix and place, seem to be common. They result from mixing the different crude sources. Some evidence indicates that equipment changes, such as using drum plant mixing in which the aggregate and asnhalt are added to a drum simultaneously, can result in a softer asphalt with a higher moisture content. The intro- duction of vibratory compactors, which densify by dynamic energy, requires a different compaction process than steel tandem rollers. There are many variables that can affect an asphalt: cement, fines, aggregate, temperature of mix and roll, etc. More research is needed to identify and clarify the role of variables. More investigation of the compaction process is necessary. (2) Preplaced Aggregate Concrete and Portland Cement Grout. This is essentially a special application of Portland cement concrete; therefore, the investigations relating to Portland cement can also result in better use of this type of concrete. By investigating the performance of past, present, and future projects using preplaced aggregate and Portland cement grout, improved techniques and other applications should be found. (3) Soil Cement. Soil cement is also a special use of Portland cement and additional investigation can create an understanding of how to use local soils, especially the very fine and clay type soils, successfully. 388 (4) Sulfur Cement Cagncrete and Grout. With the increased production of sulfur, as a result of refining more sour crude, larger quantities of sulfur become available. This makes sulfur cement concrete and grout more economically competitive for many special uses. Ongoing research and testing is aimed at improving sulfur-asphalt materials by developing additives to improve physical properties, such as those that allow mixing at temperatures above 160° Celsius to prevent dehydrogenation. In sulfur concrete develop- ment, the discovery of other plasticizers to improve its physical properties and upgrade its heat resistance is an important activity. e. Structural and Sheet Metals. (1) Steel. Much of the effort in the research and development of steel and steel products for coastal construction is devoted to the metal- lurgy in steelmaking, in order to develop products that are more corrosion resistant when exposed to the marine environment. Progress has been made with recent development of ASTM grades A242 and A588, using small amounts of vanadium, zirconium, columbium and titanium. These alloys exhibit improved strength and yield values; however, the cost of these products is high and, with the improved protective systems available (both coatings and cathodic protection), very little of these steel alloys is produced. Studies in the application and control of cathodic protection are ongoing to improve the understanding of hydrogen imbrittlement and stress corrosion cracking of metals, that may lead to greater use of structural steel in future coastal structures. (2) Aluminum and Copper. The studies and investigations of aluminum and copper, as well as other metals, are similar to those of steel. Much of the research work is concerned with a better understanding of the physical- chemistry of the oxide films that are responsible for the passivity and corrosion resistance of these metals. These studies may lead to new alloys and resulting allotropic modifications that might improve corrosion re- sistance as well as enhance some physical properties of the metals, in- cluding resistance to halogen and acidic ions. There is so much research in progress that it is difficult to estimate at this time what new knowledge may contribute to the improved use of metals in a marine environment. f. Wood. Because wood is produced by nature under various uncontrolled environmental conditions, the product is highly variable. Also, the fact that the tree is alive and produces wood of different properties at different ages complicates the analysis of properties of wood. Recent investigations on the strength properties to determine the material variability of clear wood are based on the statistical probability of sampling. (1) Elastic Parameters. Present design often involves curved members and three dimensional stress distributions. Therefore, recent emphasis has been directed toward the determination of strength and elastic characteristics of wood in all the principal directions. Prediction equations have been developed recently which allow the estimation of all the elastic parameter values of wood (Bodig and Goodman, 1973). Also, there is consider- able interest in predicting the elastic and strength characteristics of wood at any arbitrary ring and grain angle. 389 The determination of the elastic parameter values is based on the linear part of the stress-strain curve. For ultimate stress design, the knowledge of the nonlinear part of the stress-strain curve is very important. Investi- gation is also being done on the stress interaction behavior of wood. One of the problems associated with the theoretical prediction of the strength of wood is the lack of understanding of its mechanism of failure. Fracture mechanics of wood as well as the concept of energy of distortion limitation, are also being investigated. (2) Time-Dependent Characteristics. Because of the time-dependent stress-strain behavior of wood a large amount of investigation has been concerned with the rheological properties of this material. Nonlinear time- dependent relationships, cyclic loads, and cyclic environmental factors all complicate these relationships. Among the various rheological properties, creep behavior appears to be the property most often needed in designing with wood. The effect of duration of load on the strength properties also is being investigated. Dynamic forces act for a very short duration and under these conditions wood appears to be stronger and stiffer than under static loading. (3) Wood Composites. When compared to other construction materials, wood is one of the most efficient materials available on a pound per pound basis in stiffness and strength along the grain. However, its efficiency is much lower if across-the-grain direction is considered. Thus for specific engineering purposes it is necessary to rearrange the wood in relation to its natural form. This necessitates the manufacture of composites such as laminated beams, plywood, particleboard, hardboard, and fiberboard. Further modifications can be made by high density overlays and impregnations and preservatives. Some investigation and testing of laminated wood utilizes a proof-loading concept to establish the laminating combinations and their associated design stress. The research is intended to determine what tensile proof load should be used in order to justify strength levels and what percentage of the tension zone laminations should be subject to the proof load level. In order to utilize more flexibility in laminating combinations, a project is in progress which will provide criteria for combining different species. g. Plastics. The number of plastic materials and resins available today is so great and the variety of synthetics available in each family of plastic resins is so large that it is virtually impossible to identify significant investigation and research that is ongoing and of importance to coastal engineering materials development. Investigations and development occur in three general areas: processing and machinery, new resins, and resin modifications by additives. (1) Processing and Machinery. The development of new resins will not lead to an improved product until the machinery for processing such resins or modified resins can be developed. The new machinery will control the plastic manufacturing in a manner to properly produce a given product with the required physical properties. 390 Molding machines have been developed to mold liquid polymers and tech- nology is now being offered for injection molding of ultrahigh molecular weight polyethylenes. Systems for extruding polypropylene using water cool- ing of the bubble to obtain good toughness and high clarity are being de- veloped. A new development in injection molding is making a solid skin of one type of plastic and a foamed core of another. The manner in which plastics are made impacts on the physical properties of a material such as impact resistance, flexural strength, and heat distortion, permitting these properties to be substantially improved with improved processing capability. The improvement of physical properties will provide for a longer service life of the present use of both rigid and flexible plastics. As flexural strength, resistance to impact and heat distortion are increased, plastics may find an increasing use as structural members. (2) New Resins. Polyester resins form a large family of resins. In the manufacture of resins, three basic controls (i.e., density or degree of crystallinity, molecular weight, and molecular weight distribution), result in a great variety of resins. The abundance of glycols and dibasic acids de- veloped from petroleum intermediates provides a wide latitude in designing polyester resins to meet specific requirements. Unsaturated polyesters can compete with epoxies, phenolics, and other plastics in electrical, physical and mechanical properties. These resins predominate in applications requir- ing corrosion resistance. For example, nonair-inhibited types are used as a material in boat hulls, bouys, and decks, and for coating wood, concrete, metals, and other structures. High temperature resistant resins such as linear aromatic polyesters represent another new development. This particular polymer also has a high resistance against most organic solvents. Polyethylene has a very simple molecular structure, but it is capable of almost infinite variation and modification. The most recent development has been in the very high density polyethylene resins that result in a hard crystalline character. These developments may result in improved properties such as impact resistance, tensile strength, and abrasion resistance for use in bouys, fenders and bumpers, and unreinforced pipe. (3) Resin Modifications by Additives. Virtually all resins will have different properties due to the incorporation of additives. Antioxi- dants are used to prevent degradation of resins at high temperature. Ultra- violet stabilizers prevent deterioration in atmospheric exposures. Fillers are used for their reinforcing properties, such as the use of chopped glass fibers to increase strength and stiffness. Air may be considered a filler when injected into a resin during processing to produce a cellular or foamed plastic. Dispersion resins are fine particle resins which can be dispersed in plasticizers to produce liquid systems that are essentially 100 percent solids. These systems are used in the manufacture of protective coating and paint systems. Many of these systems are used to coat, impregnate or saturate fabrics and yarns as well as to coat paper, and leather. New developments in the use of plastics in coastal structures will be continuous for many years to come since a large variety of plastic resins are available, their molecular structure can be rearranged to form new plastics, 39| and the physical properties af the new plastics can be changed and improved through the manufacturing process and the addition of additives and plasti- cizers. (4) Geotextile Filters. The development, investigation and testing of fabrics is fragmented and there are many activities overlapping in effort. The manufacture of filter fabric is changing in some instances due to the ongoing development of nonwoven fabrics with controllable thickness, elonga- tion, and filtration capabilities. Methods are being investigated to char- acterize fabric as to the size and shape of openings and the details of clogging of the fabric. Tear propogation in fabrics is being studied. Mechanical property analysis to indicate the amount of deformation that a fabric will undergo is being performed. Information about anchoring to indicate the required friction between the fabric and the soil is also being investigated. Filtration mechanisms (and particularly the soil structure arrangement resulting from the waterflow), flow rate, permeability, and piping are being evaluated and laboratory test methods are being recommended. The results of these investigations and others that will come along in the future will provide data for expanded and better use of fabrics. h. Protective Systems. (1) Coatings. One of the principal means of preventing deteriora- tion of structures is through the use of protective coatings. Coatings may be specified on a formulation basis, on a performance basis, or by a combina- tion of the two. The formulation-type specification does not take advantage of the manufacturer's experience and formulating knowledge, the responsi- bility for obtaining a suitable coating being the specification writer's and his technical sources. The principal alleged merit of a performance-type coating is that it does take advantage of the manufacturer's knowledge and experience and may be a real advantage if the manufacturer is highly ex- perienced in formulating coatings for the particular contemplated usage. A principal difficulty with performance-type specifications is that acceptance tests, which purport to show that a coating is satisfactory for a specific use, must necessarily be finished in a short time and frequently have little significance in predicting actual performance. Performance tests include flexibility, hiding power, immersion resistance, gloss, resistance to weather or salt spray tests. The development of improved coating systems involves three areas of investigation and testing: surface preparation, coating application tech- niques and improved materials. In many situations environmental constraints have required innovations and improvements in all three areas of coating systems development. (a) Surface Preparation. Surface preparation is accomplished in many ways: solvent cleaning, hand and power-tool cleaning (wire brushing), pickling, flame cleaning and blast cleaning (sandblasting). Good coating performance requires good adhesion to the structure surface. Preparing the surface for coating application is critical. In solvent cleaning, mineral spirits are frequently used but must be sufficiently refined as to not leave oily residues upon evaporation. Solvents that leave 392 no residue on a surface ta impede the hond of coating require additional investigation. However, study in this area is limited as solvent cleaning is usually used with other surface preparation processes. Hand and power-tool cleaning of metal surfaces is widely used; however, this process usually produces some areas of polished metal, which are not conductible to good coating adhesion. Developmental studies are being done in an effort to devise means of removing loose contaminating particles from a structure surface by designing wire tips for brushes that will remove con- taminants and improve brush wear. In pickling, acids such as sulfuric, hydrochloric, phosphoric and nitric are used. Inhibitors are added to minimize metal loss. However, acids leave considerable residue on metal surfaces that can cause coating adhesion problems. The elimination of residues by hot-water rinsing helps but rede- posited salts or absorption of atomic hydrogen may cause metal embrittlement. Means to prevent these possibilities must be considered. Flame cleaning removes only loose rust particles and grease, therefore it must be followed by wire brushing and coating application while the surface is dry but cool. Because this process has a high cost, it is not used to a great extent and little improvement in its use is being studied. Blast cleaning is the most effective method of cleaning metal surfaces. The degree of blast cleaning can be determined by type of blasting material, the pressure used in blasting,and the amount of time of blasting per unit area. The metal surface anchor pattern developed as a result of blast cleaning can be controlled. Certain coating systems may require a deep anchor pattern, others a shallow anchor pattern. Some blasting materials produce a rounded anchor pattern while others a sharp pattern. Because different types of coating primers require different adhesion conditions, surface preparation must be considered as a part of the coating system. (b) Coating Application Techniques. Coating application techniques are an integral part of a protective coating system. As new and better coating systems are developed,new application systems must also be created. Application systems presently in use are brush, roller, various spray methods, flow and electrostatic processes. The electrostatic processes came about with the development of plastic resins which are applied in the dry powder form. This application system involves a specific surface prepa- ration process. Still in the development and improvement stage is an im- provement in the process that will produce a required thickness of a near perfect coating, without pinholes or holidays, using a variety of plastic resins. Present electrostatic applications are very good but the adaptability of this procedure to a wider variety of resins or the development of a greater number of coating resins for use in this process must continue. (c) Improved Coating Materials. Asphalt coatings consisting of a dispersion of high molecular weight hydrocarbon compounds (asphaltenes) in heavy residual oils are made into asphalt enamels,hot applied, solvent-reduced asphalt coatings and emulsions. Because the asphalt residue, from which the coatings are made, is used as a raw material for many other products, the cost of such coatings is rising and there is relatively little asphalt coating research and development activity. 393 Coal-tar pitch, the residue from distilled coal tar, is used to manu- facture coal-tar coatings by cutting back the pitch with coal-tar solvents and usually adding mineral filler (extender pigments) such as magnesium Silicate. Most recent developments of the use of coal tar in coating systems is in the coal-tar epoxy systems. These systems contain epoxy resins, pigments, solvents, curing agents, coal-tar pitch and gelling agents. The broader use of coal-tar pitch with a greater variety of resins is continually under development at present. The development of plastic resins for use in new coating formulations is part of the research and development activities discussed in Section IX, Plastics. (2) Cathodic Protection. Maximizing the efficiency of corrosion control requires a thorough understanding of the environment and its vari- ability to which structural materials are exposed. This is particularly true of metals. However, environmental considerations are also important in con- sidering the durability of all construction materials. (a) Environmental Variability. Optimizing cathodic protection systems in the marine environment requires a detailed knowledge of the seasonal variability of dissolved oxygen, temperature, and the saturation rate of the water with respect to carbonates. Although complete protection can and is being achieved on many structures without any prior knowledge of these variables, the design of the most economical system utilizing a com- bination of impressed current, sacrificial anodes, and coatings is not possible without detailed knowledge of the environmental conditions. The four variables important to corrosion for which there exists a large enough data base to permit general surface water mapping of the oceans are temperature, salinity, dissolved oxygen, and pH. Other variables may also be of importance but enough data are not yet available to significantly evaluate their impact on a global scale. Premature anode material failures as a result of variation in environ- mental conditions are being examined in more detail. Attention is being given to electrochemical reactions and conditions at the anode-environment interface when chloride and sulfate ions are discharged in the anodic process, affecting the anode material. (b) Buried and Embedded Steel. Although some ten cathodic protection criteria for buried steel structures have been used throughout the world, a universally acceptable criterion is still not available. Frequently different criteria give conflicting evaluations of the state of protection. This situation has been due primarily to the lack of suitable electrochemical procedures to monitor and evaluate the actual state of protection at the structure-soil interface. A great deal of investigation of this problem, both in the field and laboratory, is being done and reported regularly in the literature. Some studies indicate that the current density for cathodic protection of embedded steel in concrete is controlled primarily by the rate of oxygen diffusion through the concrete. Measurements indicate that the resistance to oxygen diffusion may be ten times higher through the interface between cement paste and steel than through the concrete cover. 394 Studies to provide a better understanding of the electrochemical and the electrode kinetics reactions at the surface of the metal-environment inter- face and to improve field measurement techniques are ongoing in many places in the world. 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UNITED STATES STEEL CORPORATION, "Steel Sheet Piling Design Manual," Publication No. ADUSS 25-3848-03, Pittsburgh, Pa., Apr. 1972. 403 ASTM designation A36-77 A131-78 A242-79 A252 A283-79 A284-77 A328-75a A440-77 A441-79 A514-77 APPENDIX A SPECIFICATIONS AND APPLICATIONS FOR STEEL SUTTABLE FOR MARINE SERVICE. Title of standard Standard Specification for structural steel Standard Specification for structural steel for ships Standard Specification for high-strength, low- alloy structural steel Standard Specification for welded and seamless steel pipe piles Standard Specification for low and inter- mediate tensile strength carbon steel plates, shapes, and bars Standard Specification for low and inter- mediate tensile strength carbon- silicon steelplates for machine parts and gen- eral construction Standard Specification for steel sheet piling Standard Specification for high strength, structural steel Standard Specification for high-strength low- alloy structural Manganese vanadium steel Standard Specification for high yield- strength, quenched and tempered alloy steel plate, suitable for welding 405 Application Bridges, bulkheads, general structures Ship construction, tanks (shapes, plates, rivets) Structures, form for cast in place concrete piles General structure, tanks Machine parts, general construction Sheet piling, dock walls, and cofferdams Bridges Bridges, buildings; weight savings and added durability Welded bridges and other structures A529-75 A572-79 AS73 A588-80a A633-79a A690-77 A699-77 A709-80 A710-79 Standard Specification for 42,000 psi (290 MPa) minimum yield point {1/2-in (12.7 mm) maximum thickness} Standard Specification ~ for high-strength low- alley columbium- vanadium steels of structural quality Standard Specification for structural carbon steel plates of improved toughness Standard Specification for high-strength low- alloy structural steel with 50,000 psi minimum yield point to 4-in thickness Standard Specification for normalized high- strength low-alloy structural steel Standard Specification for high-strength, low- alloy steel H-piles and sheet piling for use in marine environments Standard Specification for low-carbon manganese-molybdenum - columbium alloy steel plates, shapes, and bars Standard Specification for structural steel for bridges Standard Specification for low-carbon age- hardening nickel - copper - chromium - molybdenum-columbium and nickel-copper- columbian alloy steels 406 Buildings Bridges, building structures Steel plates and sheet piling Bridges, buildings; weight savings and added durability Serves at AEC and higher Dock walls, seawalls, bulkheads; providing 2 to 3 times greater resistance to seawater splash zone than ordinary CS General application; grades 3 and 4 suitable for temperature down to -45°C Carbon and high strength low alloy steel plates and sheets Plates, shapes and bars for general application OO a, APPENDIX B MECHANICAL PROPERTIES OF ROUND WOOD PILES TREATED WITH PRESERVATIVES FOR USE IN SALTWATER 1. Source of Information The Civil Engineering Laboratory at the Naval Construction Battalion Center, Port Hueneme, California,.investigated the effects of various commer- cial preservative treatments on the mechanical properties of wood. The in- vestigation and results are described below in excerpts from Eaton, Drelicharz and Roe (1978). 2. Preservative Treatments "Thirty-five peeled Douglas fir logs as nearly alike as feasible were selected from on-hand supplies and cut into pieces approximately 30 feet long, nominally 12 inches in diameter at the butt end and 7 inches in diameter at the tip end. These were separated into seven lots of five piles each. The seven different lot treatments were: (a) Untreated, (b) standard creosote treatment, (c) ACA, 2.5 1lb/cu ft of sapwood, (d) ACA, 1 1b/cu ft of sapwood, followed by kiln drying, followed by standard creosote treatment, (e) ACA, 1 1lb/cu ft of sapwood, followed by air drying, followed by standard creosote treatment, (£) CCA, 1 lb/cu ft of sapwood, followed by kiln drying, followed by standard creosote treatment, and (g) CCA, 1 1b/cu ft of sapwood, followed by air drying, followed by standard creosote treatment. All preservative retentions met the minimum American Wood Preservers' Associ- ation requirements except for the dual-treated CCA + creosote, both air- and kiln-dried (see Table 1)." "Forty peeled southern pine logs as nearly alike as feasible were selected from on-hand supplies and cut into forty pieces approximately 30 feet long, 12 inches in diameter at the butt end, and 7 inches in diameter at the tip end. These were separated into eight lots of five piles each. Seven lots were given the same levels of treatment as the seven lots of fir. An eighth treat- ment - 2.5 1b of CCA/cu ft: of sapwood - was used on the remaining eighth lot. All preservative retentions met the minimum American Wood Preservers' Associ- ation requirements." Note that the retentions for some preservatives were well above the speci- fied minimums. 407 Table B-1. Preservative retention of marine piles within a l-inch depth. Average Preservative Retention of Five Piles per Treatment 2 | Specific pet l, Treatment Gravity Chromium | Copper | Arsenic Untreated Creosote 2.5 ACA 1.0 ACA, kiln, creosote 1.0 ACA, air, “creosote TOP ECARMKaline creosote aOMCCARe ate. creosote 2.5 CCA Sa & (Ss) (=) SES Soe Oo oO i=) S) eH woe eH © j=) l=) Oo woo Untreated Creosote 2.5 ACA 1.0 ACA, kiln, creosote 1AORAGAR ane creosote 1 ORCCAR a Kiline creosote TAORECAR anit. creosote 1 AcA - ammoniacal copper arsenate CCA - chromated copper arsenate 2 Number represents pounds of chemical per cubic foot of sapwood. 3. Bending Tests of Full-Sized Piles "The 75 piles were then destructively tested at the Forest Research Lab- oratory, Corvallis, Ore., in a random chronological manner." "Piles were selected randomly for testing. They were loaded into a 600,000-1b capacity, universal testing machine from the Civil Engineering Department of Oregon State university. If a pile was curved, it was rotated 408 before the loading procedure until there was no horizontal curve. The load- ing heads were loaded until they almost touched the pile, load and deflection recording devices were zeroed, and circumferences were measured at the tip, middle, and butt of each pile. Moisture contents of untreated or creosote- treated piles were measured with a resistance-type moisture meter near a loading head at a depth of 0.5, 1, 1.5, 2, and 2.5 inches." "Data were recorded in two ways: (1) by means of a strip chart attached to the universal testing machine and written data sheets, and (2) a magnetic tape, digital recorder and microphone provided by CEL. The tape reel number, tape footage, date, time and specimen numbers were recorded on the data sheet, and the tape recorder was set for recording. The specimen number, date, and weather report were spoken into the microphone, and some sounds were recorded of the breaking piles. The loading rate was 0.53-in./min until fail- ure when the head speed was increased until 10 inches of deflection occurred. Maximum breaking load (P,4,) was recorded on the data sheets as were abnormal- lities such as severe slope of grain or overabnudance of knots, and the type of failure (i.e., compression, tension, or shear)." "After these bending tests, a 4-ft-long butt specimen and a 3-in.-long cross section near the failure were cut from each pile. The 4-ft-long speci- mens were sent to CEL and the 3-in.-long sections were saved for preservative analyses. Moisture content specimens were taken near the point of failure. Salt-treated and untreated specimens were oven-dried. The Karl Fischer method was used to determine moisture contents of creosote and salt-treated speci- mens. Sections of piles from the vicinity of failure points were cut and saved." 4, Compression Tests on Piles Segments "The 4-foot butt specimens obtained earlier were squared off with a table chainsaw to a length of 45 inches. The specimens were submerged in water in a retort and 90 psi of pressure applied to bring the wood to its fiber satur- ation point. This water-impregnation treatment required 1 day for pine and 1 week for Douglas fir. Moisture contents of creosoted specimens were recorded with five readings at 1/2-inch-depth increments up to a total depth of 2-1/2 inches in the middle of a piece 2 feet from its end. The moisture content of dual-treated piles was assumed to be similar to creosote-treated material. The moisture content of salt-treated piles was assumed to be similar to the untreated specimens. The average moisture contents after pressure treatment with water were 30% for southern pine and 28% for Douglas fir." "The length and circumference at butt and tip of each specimen was measured. Loading to failure was at the rate of 200 kips/min. The location of each failure was recorded." 5. Results "Table 2 shows the data obtained from this program. Table values are based on a limited number of piles, selected originally for high quality appearance and apparent low variation from pile to pile. Thus, the table values may be higher than they would be if unselected run-of-the-mill piles were used. As can be seen, there was a definite decrease in the mechanical properties of the wood with treatments, some as high as 55%." 409 Table B-2. Average mechanical properties of piles. Flexural Properties Average Type of Modulus of | Absorbed | Compressive Treatment Elasticity Energy Strength, in Flexure in ne GPa Flexure MPa kJ/m3 Untreated Creosote ACA dual2 CCA dual? ACA Untreated Creosote ACA dual2 CCA dual2 ACA CCA 1No value is provided because of the large spread in measured values for a small number of samples. 2Includes both air-dried and kiln-dried specimens (5 each). "Table 2 may be useful to the designer and planner. Data on strength of piles found in handbooks usually refer to untreated piles. A designer can obtain from Table 2 a rough estimate of the ratio of strength for his choice of species and treatment compared to that of the stronger untreated piles. Then the number of piles required for the job can be estimated." 6. Conclusions "For Douglas fir piles, it is concluded that: (a) Dual treatment (ACA and creosote or CCA and creosote) or treatment with only ACA will reduce some mechanical properties of a pile more than treatment with creosote. For specific numerical reduction refer to Table 2. (b) Of the two dual treatments, CCA and creosote reduces some mechanical properties of a pile more than ACA and creosote (refer EOmLabLerZ (c) In dual treatments, kiln drying is more deleterious than air drying." ; 410 "For southern pine piles, it is concluded that: Dual treatment (ACA and creosote or CCA and creosote) or treat- ment with ACA only are more deleterious to more mechanical proper- ties than treatment with creosote (refer to Table 2)." Recommendations "Tt is recommended that: (a) In areas where piles are destroyed mainly by mechanical means, creosote-treated piles should be considered. (b) In areas where piles are destroyed mainly by biological attack and it is known that dual-treated piles will last suf- ficiently longer than creosoted piles, the additional expense will be justified. (c) Accurate records should be kept of randomly placed pile treatments and of installation and removal dates so that a better selection of treatments could be made." 4ll APPENDIX C GEOTEXTILE FILTER TESTS 1. Tensile Strength and Elongation Test Test five Stronger Principal Direction (SPD) and five Weaker Principal Direction (WPD) samples, unaged, in accordance with ASTM Standard D 1682-64 Breaking Load and Elongation of Textile Fabric-Grab Test Method. The jaws shall be 2.54 centimeters (1 inch) square and the constant rate of travel 30.5 centimeters (12 inches) per minute. Care should be exercised to make sure the fabric is properly alined to the jaws. If not properly alined, the results will be inaccurate. Test should be conducted at 22.8° +2° Celsius (73° +3° Fahrenheit). 2. Seam Breaking Strength Test five unaged samples in accordance with method ASTM Standard D 1683-68, using 2.54-centimeter square jaws and 30.5 centimeters per minute constant rate of travel. 3. Puncture Strength Test five unaged samples using Standard ASTM D 751-73 and determine the puncture strength using the Tension Testing Machine With Ring Clamp, except that the steel ball should be replaced with a 5/16-inch diameter, solid steel cylinder centered within the ring clamp. 4. Burst Strength Test five unaged samples in accordance with ASTM Standard D 751-73 and determine the bursting strength using the Diaphragm Test Method. 5. Abrasion Resistance Test five SPD and five WPD unaged samples in accordance with ASTM Standard D 3884-80 (formerly D 1175-71) using the "Rotary Platform, Double Head" method. The abrasive wheels must be the rubber-base type equal to the CS-17 "Calibrase" manufactured by Taber Instrument Company. The load on each wheel must be 1 000 grams and the test must be continued for 1 000 revolutions. After abrasion determine the residual tensile strength by the l-inch Ravelled Strip Method of ASTM D1682-64. 6. Freeze-Thaw Test Subject five SPD and five WPD samples, 10.2 +0.51 by 15.2 +0.51 centi- meters (4 +0.2 by 6 +0.2 inches), unaged, to 300 freeze-thaw cycles as des- cribed in test method CRD-C 20. Each cycle should be a duration of 2 hours +4 minutes duration. Then test samples using ASTM Standard D 1682 Grab Test Method as described in 1. above. 7. High Temperature Test Place five SPD and five WPD samples, 10.2 +0.51 by 15.2 40.51 centimeters, unaged, in a forced draft oven at 82.29 +2° Celsius (180° +3° Fahrenheit) for 48 +2 hours. Then test each sample at the test temperature using ASTM Standard D 1682 Grab Test Method as described in 1. above. 4l2 CLOW, Temperature Test Place five SPD and five WPD samples, 10.2 +0.51 by_15.2 +0.51 centimeters, unaged, in a refrigerator at -17.8° +2° Celsius (0 +3° Fahrenheit) for 48 £2 hours, then test each sample at the test temperature using ASTM Standard D 1682 Grab Test Method as described in 1. above. OR Ncid nest Submerge five SPD and five WPD samples, 10.2 +0.51 by 15.2 +0.51 centi- meters, unaged, in a 1-liter glass beaker filled to within 5.1 centimeters (2 inches) of its top, with a solution of sufficient hydrochloric acid in about a liter of distilled water to produce a pH of 2 +0.1. Cover the pean with a ree plese and place in a constant temperature bath at 62. 8 +2° Celsius (145° +5° Fahrenheit). Using a 0.635-centimeter glass tube inserted into the spouted beaker to within 1.27 centimeters of the beaker bottom, air is bubbled gently through the solution at the rate of one bubble per second continuously for 14 days. The solution should be changed every 24 hours, with the new warmed to 65.6. +.5° Celsius (150° +1°Fahrenheit) before replacing the old solution. Test each sample then for tensile strength and elongation using ASTM Standard D 1682 Grab Test Method as described in 1. above. 10. Alkali Test Submerge five SPD and five WPD samples, 10.2 +0.51 by 15.2 +0.51 centimeters, unaged, in a l-liter glass beaker filled to within 5.1 centi- meters of its top, with a solution of equal amounts of chemically pure sodium hydroxide and potassium hydroxide dissolved in about a liter of distilled water to obtain a pH of 13 +0.1. Cover the beaker with a watch glass and place in a constant temperature bath at 62. 8° +2° Celsius. Using a 0.635-centimeter glass tube inserted into the spouted beaker to within 1.27 centimeters of the beaker bottom, air is bubbled gently through the solution at the rate of one bubble per second continuously for 14 days. The solution should be changed every 24 hours, with the new solution warmed to 65.6 +0.5 Celsius before replacing the old solution. Test each sample then for tensile strength and elongation using ASTM Standard D 1682 Grab Test Method as described in 1. above. 11.: JP-4 Fuel Test Submerge ten SPD and ten WPD samples, 10.2 +0.51 by 15.2 +0.51 centi- meters, unaged, in JP-4 fuel at room temperature for 7 days. Test each sample then for tensile strength using ASTM Standard D 1682 Grab Test Method as described in 1. above. 12. Determination of Equivalent Opening Size (E.0.S.) a. Calhoun Method, 1972. Based on the Calhoun (1972) method, five unaged samples shall be tested. Obtain about 150 grams of each of the following fractions of a sand composed of sound, rounded-to-subrounded particles: 413 U.S. Standard Sieve Number Passing Retained On Passing Retained On Passing Retained On 10 20 30 40 50 70 20 30 40 50 70 100 100. 120 The cloth shall be affixed to a standard sieve having openings larger than the coarsest sand used, in such a manner that no sand can pass between the cloth and the sieve wall. The sand shall be oven dried. Shaking shall be accomplished as described in EM 1110-2-1906, Appendix V, paragraph 2d(1)(g), except shaking shall be continued for 20 minutes. Determine by sieving (using successively coarser fractions) that fraction of sand of which 5 percent or less by weight passes the cloth; the equivalent opening size of the cloth sample is the "retained on'' U.S. Standard Sieve number of this fraction. b. Corps of Engineers 1977 Guide Specification Method. Five unaged fabric samples shall be tested. Obtain 50 grams of each of the following fractions of standard glass beads: U.S. Standard Sieve Number Designated _ Designated EOS Passing Retained On EOS Passing Retained On 20 18 20 70 60 70 30 25 30 100 80 100 40 35 40 120 100 120 50 AS 50 Suitable glass beads can be obtained from: Cataphote Division Ferro Corporation P.O. Box 2369 Jackson, Mississippi 39205 Telephone: (601) 939-4631 Within each size range, 98 percent of the beads should be within the specified range. The fabric shall be affixed to a standard sieve 8 inches in diameter having openings larger than the largest beads to be used in the test. The fabric shall be attached to the sieve in such a manner that no beads can pass between the fabric and the sieve wall. Shaking shall be accomplished as described in paragraph 2d(1)(g), Appendix V, EM 1110-2- 1906, except the times for shaking shall be 20 minutes. Determine by sieving (using successively coarser fractions) that size of beads of which 5 percent or less by weight passes through the fabric; the equivalent opening size, EOS of the fabric sample is the "retained on" U.S. Standard Sieve number of this fraction. : 414 13. Determination of Percent of Qpen Area (POA) Each of five unaged samples should be placed separately in a 2 by 2- inch glass slide holder and the image projected with a slide projector on a screen. Select a block of 25 openings near the center of the image and measure to the nearest 25.4 micrometers (0.001 inch) the length and width of each of the 25 openings and the widths of two fibers adjacent to each opening. The percent open area is determined by dividing the sum of the open areas of the 25 openings by the sum of the total area of the 25 openings and their adjacent fibers. 14, Determination of Gradient Ratio (GR) A constant head permeability test shall be performed in a permeameter cylinder on soil specimens representative in classification and density of those materials to be protected, and in accordance with EM 1110-2-1906, Appendix VII, with the following modifications: (1) A piece of hardware cloth with 0.64-centimeter (0.25 inch) openings shall be placed beneath the filter fabric specimen to support it. The fabric and the hardware cloth shall be clamped between flanges so that no soil or water can pass around the edges of the cloth. (2) The soil specimen shall have a length of 10.16 centimeters (4 inches). Piezometer taps shall be placed 2.54 centimeters below the fabric, and 2.54, 5.08, and 7.62 centimeters above the fabric. (3) Tapwater shall be permeated through the specimen under a constant head loss for a continuous period of 24 hours. The tailwater level shall be above the top of the soil specimen. The gradient ratio shall be determined from the readings taken at the end of the 24-hour period. (4) The gradient ratio is the ratio of the hydraulic gradient over the fabric and the 1 inch of soil immediately next to the fabric (i,), to the hydraulic gradient over the 2 inches of soil between 1 and 3 inches above the fabric (io). 415 APPENDIX D INFORMATIONAL ORGANIZATIONS Informational Sources American Association of Port Authorities (AAPA) 1612 K Street, N.W. Washington, D.C. 20006 American Concrete Institute Box 19150 Redford Station Detroit, Michigan 48219 American Institute of Timber Construction 333 W. Hampden Rd. Englewood, Co 80110 American Wood Preservers Institute 1651 Old Meadow Road McLean, Virginia 22101 National Association of Corrosion Engineers P.O. Box 218346 Houston, Texas 77218 National Forest Products Association 1619 Massasschusetts Avenue, N.W. Washington, D.C. 20036 Portland Cement Association 5420 Old Orchard Road Skokie, Illinois 60077 The Asphalt Institute Asphalt Institute Building College Park, Maryland 20740 The Museum of Comparative Zoology Harvard University Cambridge, Mass. 02138 National Research Council 2101 Constitution Avenue, N.W. Washington, D.C. 20418 The Sulphur Institute 1725 K Street, N.W. Washington, D.C. 20006 U.S. Army Coastal Engineering Research Center Kingman Building Fort Belvoir, Virginia 22060 U.S. Department of Agriculture Forest Service Forest Products and Engineering Research P.O. Box 2417 Washington, D.C. 20013 U.S. Navy Bureau of Yards and Docks Washington, D.C. 20390 416 ie ee Be APPENDIX E GLOSSARY OF TERMS ABRADED STRENGTH - The result when tested in accordance with ASTM D1682, "Breaking Load and Elongation of Textile Fabric, 1-Inch Ravelled Strip Method". One-inch square jaws at a constant rate of traverse of 12 inches per minute. ABRASION RESISTANCE - The ability of a surface to resist wear by friction. ALKALINE - The excess of hydroxyl ions over hydrogen ions. Seawater is usually alkaline. ALKALINITY - The capacity of a water to accept protons, i.e., hydrogen ions. It is usually expressed as milliequivalents per liter. ANAEROBIC - An oxygen-independent type of respiration. ANNEAL - To subject to high heat, with subsequent cooling, so as to soften thoroughly and render less brittle. ANODE - The positive pole or electrode of an electrolytic cell. AQUATIC - Growing or living in, or frequenting, water as opposed to ter- restrial. ARMOR - The outer or exposed layer of material(s) (stones, blocks, etc.) in a protective structure subjected to attack by wave or scour forces. AUSTENITIC - Having a solid solution of carbon or iron carbide in iron as a constituent of steel under certain conditions. BANK - (1) The rising ground bordering a lake, river, or sea; of a river or channel, designated as right or left as it would appear facing downstream. (2) An elevation of the sea floor of large area, located on a Continental (or island) Shelf and over which the depth is relatively shallow but sufficient for safe surface navigation; a group of shoals. (3) In its secondary sense, a shallow area consisting of shifting forms of silt, sand, mud, and gravel, but in this case it is only used with a qualifying word such as "'sandbank" or ''gravelbank". BASIN, BOAT - A naturally or artificially enclosed or nearly enclosed harbor ‘area for small craft. BATHYMETRY - The measurement of depths of water in oceans, seas, and lakes; also information derived from such measurements. BAY - A recess in the shore or an inlet of a sea between two capes or head- lands, not as large as a gulf but larger than a cove. BEACH - The zone of unconsolidated material that extends landward from the low water line to the place where there is marked change in material or physiographic form, or to the line of permanent vegetation (usually the effective limit of storm waves). The seaward limit of a beach - unless otherwise specified - is the mean low water line. 417 BEACH EROSION - The carrying away of heach materials by wave action, tidal currents, littoral currents, or wind. BENTHIC - Pertaining to the subaquatic bottom. BENTHOS - A collective term describing: (1) Bottom organisms attached or resting on or in the bottom sediments. (2) Community of animals living in or on the bottom. BIOASSAY - The use of living organisms as an index to determine environ- mental conditions. BIOCHEMICAL OXYGEN DEMAND (BOD) - The amount of oxygen required by the biological population of a water sample to oxidize the organic matter in that water. It is usually determined over a 5-day period under stan- dardized laboratory conditions and hence may not represent actual field conditions. BIOLOGICAL RESISTANCE - Ability to resist degradation due to microorganisms. BIOMASS - The amount of living material in a unit area for a unit time. Also standing crop, standing stock, live-weight. BIOTA - The living part of a system (flora and fauna). BOULDER - A rounded rock more than 10 inches in diameter; larger than a cobblestone. See SOIL CLASSIFICATION. BOTTOM - The ground or bed under any body of water; the bottom of the sea. BREAKER - A wave breaking on a shore, over a reef, or other feature. BREAKWATER - A structure protecting a shore area, harbor, anchorage, or basin from waves. BULKHEAD - A structure or partition to retain or prevent sliding of the land. A secondary purpose is to protect the upland against damage from wave action. BUOY - A float; especially a floating object moored to the bottom, to mark a channel, anchor, shoal, rock, etc. BUOYANCY - The resultant of upward forces, exerted by the water on a submerged or floating body, equal to the weight of the water displaced by this body. BURST STRENGTH - The resistance of a fabric to rupture due to pressure applied at right angles to the plane of the fabric under specified con- ditions, usually expressed as the pressure causing failure. Burst is due to tensile failure of the fabric. CATHODE - The negative pole or electrode of an electrolytic cell. CAUSEWAY - A raised road, across wet or marshy ground, or across water. 418 CHANNEL - (1) A natural or artificial waterway of perceptible extent which either periodically gr cantinuously contains moving water, or which forms a connecting link between two bodies of water. (2) The part of a body of water deep enough to be used for navigation through an area otherwise too shallow for navigation. (3) A large strait, as the English Channel. (4) The deepest part of a stream, bay, or strait through which the main volume or current of water flows. CLAY - A fine grained soil with cohesive strength inversely related to water content. It is plastic when moist and hardens when baked or fired. See SOTL CLASSIFICATION. CLIFF - A high, steep face of rock; a precipice. CLOGGING - The phenomena causing either a reduction in, or the elimination of, the permeability of the filter. COAST - A strip of land of indefinite width (may be several miles) that extends from the shoreline inland to the first major change in terrain features. COASTAL AREA - The land and sea area bordering the shoreline. COBBLE (COBBLESTONE) - A naturally rounded stone larger than a pebble, especially one 6 inches to a foot in diameter. COLLECTOR PIPE - A pipe capable of collecting and carrying water from the soil. COLONIZATION - A natural phenomenon where a species invades an area pre- viously unoccupied by that species and becomes established. To be successful the species must be able to reproduce in that area. CONTOUR - A line on a map or chart representing points of equal elevation with relation to a DATUM. It is called an ISOBATH when connecting points of equal depth below a datum. CORAL - (1) (Biology) Marine coelenterates (Madreparia), solitary or colonial, which form a hard external covering of calcium compounds, or other materials. The corals which form large reefs are limited to warm, shallow waters, while those forming solitary, minute growths may be found in colder waters to great depths. (2) (Geology) The concretion of coral polyps, composed almost wholly of calcium carbonate, forming reefs, ‘and treelike and globular masses. May also include calcareous algae and other organisms producing calcareous secretions, such as bryozaans and hydrozoans. CORE - A vertical cylindrical sample of the bottom sediments from which the nature and stratification of the hottom may be determined. The interior material of a breakwater or groin. CREEP - To slip or become slightly displaced; specifically of metal to shift longitudinally under weight. 419 CURE - To alter industrially, as to vulcanize (rubber) oer to treat (synthetic resins) with heat or chemicals to make infusible. CURRENT - A flow of water. CURRENT, LITTORAL - Any current in the littoral zone caused primarily by wave action, e.g., longshore current, rip current. DAP - A notch cut in one timber to receive another, usually permitting the two timbers to be flush. DATUM, PLANE - The horizontal plane to which soundings, ground elevations, or water surface elevations are referred. The plane is called a TIDAL DATUM when defined by a certain phase of the tide. The following datums are ordinarily used on hydrographic charts: MEAN LOW WATER - Atlantic coast (U.S.), Argentina, Sweden, and Norway; MEAN LOWER LOW WATER - Pacific coast (U.S.); MEAN LOW WATER SPRINGS - United Kingdom, Germany, Italy, Brazil, and Chile; LOW WATER DATUM - Great Lakes (U.S. and Canada); LOWEST LOW WATER SPRINGS - Portugal; LOW WATER INDIAN SPRINGS - India and Japan; LOWEST LOW WATER - France, Spain, and Greece. A common datum used on topographic maps is based on MEAN SEA LEVEL. DENIER - A unit expressing the fineness of silk, rayon, nylon or other synthetic yarns in terms of weights in grams per 9 000 meters of length. DEPTH - The vertical distance from a specified tidal datum to the sea floor. DIKE (DYKE) - A wall or mound built around a low-lying area to prevent flooding. DOLPHIN - A cluster of piles. DUNES - (1) Ridges or mounds of loose, wind-blown material, usually sand. (2) BED FORMS smaller than bars but larger than ripples that are out of phase with any water-surface gravity waves associated with them. DURABILITY - A relative term for the resistance of a material to loss of physical properties or appearance as a result of wear or dynamic operation. ELONGATION AT FAILURE - The length of a fabric test specimen when it is broken in a tensile test (ASTM D1682-64) compared to its original length, expressed as a percent. EMBANKMENT - An artificial bank such as a mound or dike, generally built to hold back water or to carry a roadway. ENDEMIC - Native to a specific geographic area. 420 EQUIVALENT OPENING SIZE - E.Q.S. - The number of a U.S. standard sieve having openings closest in size to the diameter of uniform particles which will have 95 percent by weight retained by the fabric when shaken in a prescribed manner. EROSION - The wearing away of land by the action of natural forces. Ona beach, the carrying away of beach material by wave action, tidal currents, littoral currents, or by deflation. ESTUARY - (1) The part of a river that is affected by tides. (2) The region near a river mouth in which the freshwater of the river mixes with the saltwater of the sea. FAUNA - Animal life as opposed to flora (plant life). Generally the entire group of animals found in an area. FIBRILLATED YARN - Yarns formed of fibers from sheet plastic film. FILAMENT - A single thread (yarn) of extreme length. FILL - Fibers or yarns placed at right angles to the warp. FILTER FABRIC - A permeable fabric of synthetic fibers whose function is to retain soil and be permeable to water. FLORA - Plant life as opposed to fauna (animal life). The entire group of plants found in an area. FORESHORE - The part of the shore lying between the crest of the seaward berm (or upper limit of wave wash at high tide) and the ordinary low water mark, that is ordinarily traversed by the uprush and backrush of the waves as the tides rise and fall. FOULING ORGANISM - An organism that attaches to the surface of submerged or introduced objects regardless of whether the objects are natural or man- made. GALVANIZE - To subject to the action of electric currents; to coat with zinc. GEOTEXTILE - Any permeable textile used with foundations, soils, rock, earth or any other geotechnical material as an integral part of a man made project, structure or system. GEOTEXTILE FILTER - A permeable fabric of synthetic fibers whose function is to retain soil and be permeable to water. GRAVEL - A coarse grained, cohesionless material whose size ranges between 76.2 millimeters and the No. 4 sieve. See SOIL CLASSIFICATION. GROIN (British, GROYNE) - A shore protection structure built (usually perpendicular to the shoreline) to trap littoral drift or.retard erosion of the shore. 42l GROUND WATER - Subsurface water occupying the zone of saturation. In a strict sense, the term is applied only to water below the WATER TABLE. GULF - A large embayment in a coast; the entrance is generally wider than the length. HABITAT - The place where an organism lives. HARBOR (British, HARBOUR) -- Any protected water area affording a place of safety for vessels. HEAT BONDED - The fabric web is subjected to a relatively high temperature. The filaments are welded together at the contact points. HEAT OF HYDRATION - The heat evolved or absorbed when hydration occurs; specifically, when water is added to a calcium aluminate powder to produce cement. IMPERMEABLE GROIN - A groin through which sand cannot pass. INTERLOCKING CONCRETE BLOCK - A cast or machine produced concrete block having interengaging or overlapping edges. JETTY - (1) (U.S. usage) On open seacoasts, a structure extending into a body of water, and designed to prevent shoaling of a channel by littoral materials, and to direct and confine the stream or tidal flow. Jetties are built at the mouth of a river or tidal inlet to help deepen and sta- bilize a channel. (2) (British usage) Jetty is synonymous with "wharf" @re Monlere” LARVA - A sexually immature form of any animal unlike its adult form and requiring changes before reaching the basic adult form. LITTORAL - Of or pertaining to a shore, especially of the sea. LITTORAL DRIFT - The sedimentary material moved in the littoral zone under the influence of waves and currents. LITTORAL TRANSPORT - The movement of littoral drift in the littoral zone by waves and currents. Includes movement parallel (longshore transport) and perpendicular (onshore-offshore transport) to the shore. LONGSHORE - Parallel to and near the shoreline. MONOFILAMENT - A single filament of a manmade fiber, usually of a DENIER higher than 15. MULTIFILAMENT - A yarn consisting of many continuous filaments or strands. MUD - A fluid-to-plastic mixture of finely divided particles of solid material and water. NONWOVEN FABRIC - A textile structure produced by bonding or interlocking of fibers, or both, accomplished by mechanical, chemical or solvent means and combinations thereof excluding woven and knitted fabrics. 422 NOURISHMENT - The process of replenishing of beach. It may be brought about naturally, by longshore transport, or artificially by the deposition of dredged materials. NYLON FIBER - A manufactured fiber in which the fiber-forming substance is any long chain synthetic polyamide having recurring amide groups (-NH-CO-) as an integral part of the polymer chain. OFFSHORE - (1) In beach terminology, the comparatively flat zone of variable width, extending from the breaker zone to the seaward edge of the Continental Shelf. (2) A direction seaward from the shore. ONSHORE - A direction landward from the sea. ORGANISM - Any living individual whether plant or animal. OUTFALL - A structure extending into a body of water for the purpose of discharging sewage, storm runoff, or cooling water. OVERTOPPING - Passing of water over the top of a structure as a result of wave runup or surge action. PERCENT OPENING AREA (POA) - The visible net area of a fabric that is available for water to pass through the fabric, normally determinable only for woven and nonwoven fabrics having distinct visible and measur- able openings that continue directly through the fabric. PERMEABLE GROIN - A groin with openings large enough to permit passage of appreciable quantities of littoral drift. PIER - A structure, usually of open construction, extending out into the water from the shore, to serve as a landing place, a recreational ‘facility, etc., rather than to afford coastal protection. In the Great Lakes, a term sometimes improperly applied to jetties. PILE - A long, heavy timber or section of concrete or metal to be driven or jetted into the earth or seabed to serve as a support or protection. PILE, SHEET - A pile with a generally slender flat cross section to be driven into the ground or seabed and meshed or interlocked with like members to form a diaphragm, wall, or bulkhead. PILING - A group of piles. PIPING - The process by which soil particles are washed in or through pore spaces in drains and filters. PLASTIC FILTER - See Filter Fabric. PLASTIC FILTER FABRIC - See Filter Fabric. 423 POLYAMIDE - See Nylon Fiber. POLYETHYLENE FIBER - A manufactured fabric in which the fiber- forming substance is an olefin made from polymers or copolymers of ethylene. POLYMER - A high molecular chainlike structure from which manmade fibers are derived; produced by linking together molecular units called monomers - consisting predominantly of nonmetallic elements or compounds. POLYPROPYLENE FIBER - A manufactured fiber in which the fiber-forming sub- stance is an olefin made from polymers or copolymers of propylene. POLYESTER FIBER - A manufactured fiber in which the fiber-forming substance is any long chain synthetic polymer composed of at least 85 percent by weight of an ester of dihydric alcohol and terephthalic acid (FTC). POLYVINYLIDENE CHLORIDE FIBER - A manufactured fiber in which the fiber- forming substance is a thermoplastic derived by copolymerization of two or more vinyl monomers. PORT - A place where vessels may discharge or receive cargo; may be the entire harbor including its approaches and anchorages, or may be the commercial part of a harbor where the quays, wharves, facilities for transfer of cargo, docks, and repair shops are situated. POZZOLAN - A siliceous rock of volcanic origin, first found near Puteoli (modern Pozzuoli), Italy, used in preparing a hydraulic cement. PRECAST CELLULAR BLOCK - A cast or machine produced concrete block having continuous void(s) through the vertical plane. Normally with smooth vertical or near vertical sides (not interlocking). Some are cabled together horizontally to form a mat. PUNCTURE RESISTANCE - Resistance to failure of a fabric due to a blunt object applying a load over a relatively small area. Failure is due to tensile failure of the fibers. QUARRYSTONE ARMOR UNITS - Relatively large quarrystones that are selected to fit specified geometric characteristics, including compact dimensional proportions and a nearly uniform size, usually large enough to require individual placement. In normal cases they are placed in a layer at least two stones thick. QUAY - (Pronounced KEY) - A stretch of paved bank, or a solid artificial landing place parallel to the navigable waterway, for use in loading and unloading vessels. RESIN BONDED - The fabric web is impregnated with a resin which serves to coat and cement the fibers together. REVETMENT - A facing of stone, concrete, etc., built to protect a scarp, embankments, or shore structure against erosion by wave action or currents. RHEOLOGY - Science dealing with the deformation and flow of matter. 424 RIPRAP - A protective layer or facing of quarrystone randomly placed to prevent erosion, scour, or sloughing of an embankment or bluff toe, also the stone so used, usually well graded within wide size limits. The quarrystone is placed in a layer at least twice the thickness of the 50- percent size stone or 1.25 times the thickness of the largest size stone in the size gradation. RUBBLE - (1) Loose angular waterworn stones along a beach. (2) Rough, irregular fragments of broken rock. RUBBLE-MOUND STRUCTURE - A mound of random-shaped and random-placed stones protected with a cover layer of selected stones or specially shaped concrete armor units. (Armor units in primary cover layer may be placed in orderly manner or dumped at random.) RUNUP - The rush of water up a structure or beach on the breaking of a wave. Also UPRUSH. The amount of runup is the vertical height above stillwater level that the rush of water reaches. SAND - An earthy matrial whose grain size is between 4.76 and 0.075 milli- meters. Within this classification sand may vary from coarse to fine. Sand is cohesionless but exhibits appearance of cohesion when wet. See SOIL CLASSIFICATION. SANDCORE JETTY - A jetty, groin or breakwater in which the core material consists of sand rather than stone. SARAN = See polyvinylidene chloride fiber. SCREED - A strike board used to level or strike off concrete pavement slabs or cushion courses for block pavements. SCOUR - Removal of underwater material by waves and currents, especially at the base or toe of a shore structure. SCOUR PROTECTION - The protection at the base or toe of a structure to prevent removal of underwater material by waves and currents. SEAWALL. - A structure separating land and water areas, primarily designed to prevent erosion and other damage due to wave action. See also BULK- HEAD. § SEICHE - (1) A standing wave oscillation of an enclosed water body that continues, pendulum fashion, after the cessation of the originating force, which may have been either seismic or atmospheric. (2) An oscilla- tion of a fluid body in response to a disturbing force having the same frequency as the natural frequency of the fluid system. Tides are now considered to be seiches induced primarily by the periodic forces caused by the sun and moon. (3) In the Great Lakes area, any sudden rise in the water of a harbor or a lake whether or not it is oscillatory. Although inaccurate in a strict sense, this usage is well established in the Great Lakes area. 425 SEISMIC SEA WAVE (TSUNAMI) - A long-period wave caused by an underwater seismic disturbance or volcanic eruption. Commonly misnamed "tidal wave." SHEAR FRACTURE - An action or stress resulting from applied forces, which causes or tends to cause two contiguous parts of a body to slide relatively to each other in a direction parallel to their plane of contact. SHEET PILE - See PILE, SHEET. SHOAL (noun) - A detached elevation of the sea bottom, comprised of any material except rock or coral, which may endanger surface navigation. SHOAL (verb) - (1) To become shallow gradually. (2) To cause to become shallow. (3) To proceed from a greater to a lesser depth of water. SHORE - The narrow strip of land in immediate contact with the sea, in- cluding the zone between high and low water lines. A shore of uncon- solidated material is usually called a beach. SHORELINE - The intersection of a specified plane of water with the shore or beach. (e.g., the high water shoreline would be the intersection of the plane of mean high water with the shore or beach.) The line delineat- ing the shoreline on National Ocean Survey nautical charts and surveys approximates the mean high water line. SHOTCRETE - A pneumatically applied concrete or grout. SILT - A fine grained soil of low plasticity which may exhibit an apparent cohesion due to capillary forces. See SOIL CLASSIFICATION. SLOPE - The degree of inclination to the horizontal. Usually expressed as a ratio, such as 1:25 or 1 on 25, indicating 1 unit vertical rise in 25 units of horizontal distance; or in a decimal fraction (0.04); degrees (oe 18"); or percent (4%). SLUMP - To fall or sink suddenly. SOIL CLASSIFICATION (size) - An arbitrary division of a continuous scale of grain sizes such that each scale unit or grade may serve as a convenient class interval for conducting the analysis or for expressing the results of an analysis. SPALL - To breakup or reduce by chipping with a hammer; to chip or crumble. SPECIES - An aggregate of interbreeding populations that under natural conditions is reproductively isolated. SPLASH ZONE - The zone immediately landward of the mean higher high water level affected by the wave spray. - STONE, DERRICK - Stone heavy enough to require handling individual pieces by mechanical means, generally 1 ton and up. STRENGTH - Load capacity at failure. Depending on the usage, load may be expressed in stress, force per unit width, or force. 426 i i SURF ZONE - The area between the outermost breaker and the limit of wave uprush, TENSILE STRENGTH - The strength shown by a material subjected to tension as distinct from torsion, compression or shear. TERRESTRIAL - Of or relating to the earth and its inhabitants as opposed to aquatic. THIXOTROPIC - Becomes fluid when shaken, stirred, or otherwise disturbed and sets again to a gel when allowed to stand. TOE - The lower elevation terminus of a revetment or side slopes of a groin, breakwater or jetty. The outer limit of a scour protection mound. TREMIE - An apparatus for depositing and consolidating concrete under water consisting essentially of a tube of wood or sheet metal with a top in the form of a hopper. TSUNAMI - A long-period wave caused by an underwater disturbance such as a volcanic eruption or earthquake. Commonly miscalled "tidal wave." TURBIDITY - A condition where transparency of water is reduced. It is an optical phenomenon and does not necessarily have a direct linear relation- ship to particulate concentration. ULTRAVIOLET (UV) RESISTANCE - Ability to resist deterioration on exposure to sunlight. VERTICAL SEAWALL - See Bulkhead. VISCOSITY - (or internal friction) - That molecular property of a fluid that enables it to support tangential stresses for a finite time and thus to resist deformation. WARP - Fibers or yarns lengthwise in the fabric. WEB - The sheet or mat of fibers or filaments before bonding or needle- punching to form a nonwoven fabric. WHARF - A structure built on the shore of a harbor, river, or canal, so that vessels may lie alongside to receive and discharge cargo and passengers. WOVEN FABRIC - A textile structure comprising two or more sets of filaments or yarns interlaced in such a way that the elements pass each other essentially at right angles and one set of elements is parallel to the fabric axis. Usually has a uniform pattern with distinct and measurable openings. Commonly referred to as cloth. YARN - A generic term for a continuous strand of textile fibers, filaments or materials in a form suitable for weaving or otherwise intertwining to form a textile fabric. 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