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OL. 26, NO. 8 JUNE 1951

Public Roads

A JOURNAL O F HIGHWAY RESEARCH

s . = , Meee a

UBLISHED BY HE BUREAU OF UBLIC ROADS,

i. S. DEPARTMENT \F COMMERCE, VASHINGTON

An additional cent of gasoline tax, costing the average motorist 13 cents a week, 4 will provide many miles of better highways

IN THIS ISSUE

The Gasoline Tax in Relation to Automobile

Operation and Highway Costs.___-__.----.------- haat) Volume Changes in Sand-Gravel Concrete____..__.....__ 162 ING Wag ICA LOT bia ht Lie ee ee ee ee i Highway Soil Engineering, a motion picture. E72

Contents of this publication may be reprinted. Mention of source is requested.

A+Ji0O.U-'R N°AL © OF GH Gra weAar RESEARCH

Public Roads.

Vol. 26, No. 8 June 195) Published Bimonthly S|

} BUREAU OF PUBLIC ROADS Washington 25, D. qi

REGIONAL HEADQUARTER 180 New Montgomery S San Francisco 5, Cali

DIVISION OFFICES

No. 1. 718 Standard Bldg., Albany 7, N. Y. Connecticut, Maine, Massachusetts, New Hamj shire, New Jersey, New York, Rhode Islan and Vermont. / No. 2. 707 Earles Bldg., Hagerstown, Md. Delaware, District of Columbia, Marylan¢ Ohio, Pennsylvania, Virginia, and West Vi ginia. No. 3. 504 Atlanta National Bldg., Atlanta 3, | Alabama, Florida, Georgia, Mississippi, Nor Carolina, South Carolina, and Tennessee. | No. 4. South Chicago Post Office, Chicago 17, I Illinois, Indiana, Kentucky, and Michigan. No. 5. (NORTH). Main Post Office, St. Paul Minn. Minnesota, North Dakota, South Dakota, ar Wisconsin. | No. 5. (SouTH). Fidelity Bldg., Kansas City Mo. Iowa, Kansas, Missouri, and Nebraska. No. 6. 502 U. S. Courthouse, Fort Worth 2, Te Arkansas, Louisiana, Oklahoma, and Texas. —

No. 7. 180 New Montgomery St., San Francisco Calif. Fi Arizona, California, Nevada, and Hawaii.

No. 8. 753 Morgan Bldg., Portland 8, Oreg. Idaho, Montana, Oregon, and Washington. |

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No. 10. Federal Bldg., Juneau, Alaska. Alaska.

PuBLic Roaps is sold by the Superintendent of Documen Government Printing Office, Washington 25, D. C., at $1 4 year (foreign subscription $1.25) or 20 cents per single co Free distribution is limited to public officials actually enga: in planning or constructing highways, and to instructors highway engineering. There are no vacancies in the free

at present.

The printing of this publication has been approved by 1 Director of the Bureau of the Budget January 7, 19

BUREAU OF PUBLIC ROA U. S. DEPARTMENT OF COMMER E. A. STROMBERG. Edit

|L. L. LISTON, Transportation Economist

|} ASOLINE TAXES constitute a very “small part of the total cost of owning { operating an automobile, and revenues m gasoline taxes are falling far short of ded highway construction and mainte- ice expenditures. While other prices and ts have nearly doubled in the past 10 rs, the tax on gasoline has increased only [7 percent. It is the purpose of this study sompare trends in gasoline taxes, costs of rating an automobile, and costs of con- acting and maintaining highways.

{ previous article in PUBLIC ROADS* re- ted a study of gasoline price and tax reases during a 30-month period ending ie 30, 1948. Although there were sub- ntial gasoline price increases in all States | gasoline tax increases in 12 States dur- that period, these increases had no asurable effect on consumption of gaso- » In the 1949 study, however, no ef- t was made to establish the relation be- en gasoline costs, total vehicle operating ts, and the portion of the vehicle opera- 's dollar that ‘goes for road-user taxes. th comparisons are made here.

‘ Gasoline Prices and Taxes

tasoline prices have continued to increase te 1948, and there have been increases gasoline taxes in some States. The in- ases in gasoline prices (excluding taxes) lin State gasoline taxes during the 54- nth period from January 1946 to June 0 are shown in figure 1. This figure is extension of figure 2 in the 1949 study, ich covered the 30 months from January 6 to June 1948. The findings for the ger-period are in such complete agree- at with those of the original study that eration of the conclusions in detail would needless repetition.

e earlier study established that no gaso- ix increase has had a measurable ef- the consumption of gasoline, and ithin reasonable contemplation ap- kely to do so. Theoretically, any the cost of operating automobiles

- M. Cope and L. L. Liston. PuBLic Roaps,

3, No. 7, March 1949, p. 138.

ROADS e Vol. 26, No. 8

he Gasoline Tax in Relation to Automobile Operation and Highway Costs

BY THE RESEARCH REPORTS BRANCH

jorted by E. M. COPE, Chief, Highway Statistics Section

BUREAU OF PUBLIC ROADS

Unit costs of highway construction and maintenance have almost doubled in the last 10 years, considerably exceeding the 77-percent increase in the basic

cost of living. The price of gasoline, excluding tax, rose 62 percent in the same 10 years, but since the tax on gasoline rose less than 13 percent during this period the net effect felt by the motorist in his purchases of gasoline was an increase of only 47 percent in the total of price plus tax.

There has been a substantial increase in revenue for highways over the 10-year period, resulting from the tremendous growth in the number of motor

vehicles.

costs and the contrastingly small one in tax rates. no more highway work than did the 1940 revenue.

This has been nullified, however, by the extreme increase in highway

Current revenue will buy Yet the need is far greater,

for the constantly multiplying number of vehicles continually intensifies our

traffic problems.

The public apparently does not have a clear picture of the relation of taxes

to the total cost of owning and operating an automobile.

An analysis for a

typical passenger car indicates that the taxes represent only 11 percent of the

total ownership and operation costs—less than any other major item of cost

involved. Put in practical terms, of the 6.6 cents per mile it costs to own and

operate an automobile, all taxes combined represent seven-tenths of a cent. The gasoline tax accounts for only 6 percent of the total cost of owning and operating a car, or four-tenths of a cent per mile, and the tax rate is actually

lower in proportion to individual income now than it was in 1940. Each cent

of the gasoline tax rate costs the average motorist seven-hundredths of a cent

per mile, or about 13 cents a week—just about 1 percent of the total ownership

and operation cost.

no effect has been noted is rather obvious— the gasoline tax constitutes only about 6.5 percent of the total cost of operating an automobile (as will be shown later), and has actually been declining in terms of its re- lation to the total cost.

There were net tax increases, during the 54-month period, of from 1/2 cent to 2 cents per gallon in 23 States, and a net tax de- crease of 1 cent per gallon in one State. There were net price increases, excluding taxes, in all States during the same period. In Utah the price increase was only 1/2 cent per gallon, and in California the net price increase was only 2 cents per gallon. In other States, however, the net price in- creases were much higher—ranging from 3.4 cents per gallon in Arizona to 8.5 cents per gallon in Wyoming. Avail- able information indicates that the Utah and California’ increases were relatively small because of intense competitive condi- tions in those areas.

Relative Cost of Gasoline

It has never been possible to measure the extent of the effect of operating costs on

vehicle ownership and use. Much of the discussion and publicity on the point has centered around the cost of gasoline, prob- ably because this is an item with which the public comes in daily contact. Gaso- line taxes have assumed a disproportionate importance to the public because consider- able publicity has been given to gasoline prices and taxes when matters pertaining to them have been under study by State legislatures, and to the allegation that “gasoline is cheap—only the tax is high.”

The emphasis on gasoline taxes has tended to obscure the fact that many items of the cost of operating a motor vehicle consid- erably exceed gasoline tax payments. It is not generally recognized that both gasoline prices and gasoline tax rates have risen more slowly than general price levels. The aver- age retail price of gasoline in 1940, inelud- ing taxes, was 18.4 cents per gallon. Dur- ing the 10 years to 1950 the retail price alone, excluding taxes, increased 62 percent. It is worth noting that this increase, though substantial, was considerably less than the 77-percent increase in the cost of living reflected in the Bureau of Labor Statistics

157

STATE

ATA BA RUA sassaicsea esters cet ete ARIZONA.-- MRKANSA Sar arc seuacnees eres eae CALIFORNIA~-<c<ccceccteecevece COLORADO :esscerrsececcnceevecs CONNECTICUT -..---++-++-00+0s-

TIS INOIS ereteee res eceaes cece: INDIA NAtssste< sees oops sunnmenar

KENTUCKY: 000 sa ccmneeoaae MOUISTAIN Roe aeeecn cece racer ars AVUAMIN GS jetecae ts caso rnte sone eter MAR VIGAN ID oasccstiins emednsesice | MASSACHUSETTS:...-:..-++++++: MIC HIGIA Nitsiecesle oe creme seers MINNESOTA ...----.--+seeeee eee MISSISSIPPI: sasts-sreeesesqsoent MISSOURI: eepeneeciemeses adewslisine } NMGIN SAN Aes ee sdeeececinaee aeons NEBRASK Acssctniaseacmianetnrn nate NEVADA O10 019, 6 5'S9\e alee 6 Bin winlaialajais 4 eie,ele 5 NEW HAMPSHIRE: NEW JERSEY SOOMOOUCICII CIO UOC i NEWOME 1G Ol-trneea tea soca-o. Niontte s8d0) 42<00 oo ano ino soun oben ce NORTH CAROLINA: +++.--.5+ NORTH DAKOTA: +:++.:000000+-

OR BGO Nitec cantante seine micsehae PENNSYLVANIA «+000ess0-+0s f RHODE ISLAND «0s-++eeeeeeees SOUTH CAROLINA® + +s-ee++ SOUTH DAKOTA: +++reeeseeeeee TF NNESSEE TEXAS.:--

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DISTRICT OF COLUMBIA::::

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INCREASE IN STATE TAX RATE

Figure I.

index. In the same 10-year period the weighted average of State and Federal gas- oline taxes rose only 12.7 percent. Thus, due to the relative stability of gasoline taxes, the total cost of gasoline to the con- sumer increased only 47.3 percent. Since wages have risen considerably more than

the cost of gasoline, the consumer is actually in a better position now than in 1940 with

respect to his purchases of gasoline. The percentage increase in the cost of gasoline,

even though it was approximately five times

as great as that for gasoline taxes, was

158

Gasoline price and tax increases.

January

still 20 percent less than the percentage in- crease in the cost of living reported by the Bureau of Labor Statistics. of gasoline taxes and prices in in 1950 is given in table 1.

A comparison

1940 and

Highway Costs The economic factors that brought about increased costs of gasoline also caused in- creased costs of raw materials, wages, trans- portation, and other components of the total

price of motor vehicles, gasoline, and as- sociated products. Likewise, they brought

MMMMSINCREASE IN PRICE EXCLUDING STATE TAX

1, 1946-June 30. 1950

about sharp increases in the costs of B structing highways—a rise of 97 perce# the 10-year period from 1940 to 1950. increases in the costs of construction@ge reflected in table 2. During the same period highway nil tenance costs rose 87 percent. This fille is a composite of the relative increases 1940 to 1950 in the unit costs of the © cipal items of maintenance, which as follows: Labor, 114.27 percent; matd 56.72 percent; equipment, 72.73 percent! overhead, 67.10 percent.

June 1951 ® PUBLIC R

Table 1.—Gasoline price’ and tax changes, 1949-50

Price, | Relation of | excluding | eax ape tax to | tax | Dries total price ews :. te = : i} Cents Cents Cents Percent EN Foes. RGNRLE Cn eRe ies hte Sol ys 60-53 7h. 12.9 5.5 18.4 29.9 IR een ae Ape 20.9 6.2 BT et me 22.9 Yereentage change.............. ey | +62.0 Sig rh MATS) MP ce Qh;

ave | |

, Prices in effect in the capital cities of the States except for Maryland and Oregon, where the prices are for Baltimore » 2ortland, respectively.

Table 2.—Changes in unit costs of highway construction, 1940-50

) ra Item 1940 | 1950 | Increase | J ’ ; ; Percent }Sommon excavation: bid price, cu. yd...... 2 ig SOME nen Gee eo ; $0.21 $0.34 61.9 Soncrete pavement: bid price, sq. yd............ LESS. 3.66 | 117.9 | 3tructures: | meinrorcing steel’: bid price, Ib... 6c. s.necu cues eees et Men See 045 | 100 | 122.2 Seenctural steel: bid price, Ibm. 2. As. c.. eee cvs oe ; Se.| . 043 .139 | 120.6 memcrete:, DId. price, cu. YA) 3. 0... law ce ce ees ceo Aen De 19.170 44.620 | 132.8 BEERHECAAN GOK A771 ate Pre a ae Foe a ee le hates wie ey ea Oe ee eet : | 97.0 i |

‘igure 2 shows the relative increases in ber of jobs of different kinds done by car cost of living, the price of anew automo- dealers and independent repair shops for , the price of gasoline (excluding tax), several years. A sample group of jobs, gasoline tax rate, and the unit costs of comprising more than two-thirds of the hway construction and maintenance. It total listed, was chosen as representative | be noted that the price of gasoline did of the maintenance and repair work which increase as much as either the cost of would be done on a typical automobile dur- ng or the price of a new automobile. ing the 10-year period. These items range ft even the petroleum industry, generally from major repairs such as a complete sisidered to be one of the most efficient in engine overhaul to minor maintenance items f} economy, found it necessary to increase like washing and lubrication. The fre- price of gasoline five times as much quency of the jobs listed in the Service Job ii a percentage basis) as gasoline taxes Analysis and the experience of men familiar ire increased. with automotive maintenance and service

d A were used as guides to the number of times Automobile Operating Costs each job would be required during the life

State gasoline taxes, which are the prin- of the car. Costs, including parts, were (al source of revenue for highways, cost then obtained from the most recent flat-rate t! average automobile user about 65 cents manuals, and the prices of parts as listed iveek. This fact is of limited significance in the manual were checked locally to de- itil it is related to total costs of vehicle (aration. In order to establish the relation, 4% estimate of the cost of owning and op- ‘iting an automobile is presented in table It is not based on actual records for iy particular vehicle or group of vehicles, lt the figures are believed to be typical, {mid-1950 prices, for average operation of 1: type of automobile considered.

‘The estimate is based on a low-priced )0-model four-door sedan built by a lead- 'y manufacturer, and covers an assumed -year life for the vehicle. The automobile ‘assumed to be registered in Baltimore, i, and subject to normal taxes in that

‘'d other factors in the estimate are be-

htial factors of the estimate are stated the notes below table 3.

in estimating expenditures for repairs 0 20 f. maintenance, the Service Job Analysis Umate compiled by Motor Service Maga- ne was used. This analysis lists the num-

ia IC ROADS e Vol. 26, No. 8

termine any necessary adjustments for the Baltimore area.

The expenditures for major items—re- placement tires, motor overhaul, painting, for example—are distributed over a period of years, rather than being charged en- tirely to the year of actual expenditure, because the benefit of each expenditure ex- tends beyond the year in which it was made. The cost of the motor overhaul, for instance, occurs in the seventh year but is distributed over the seventh through the tenth years.

No costs for car financing, for fines and forfeitures, or for automobile club member- ship are included, nor is any interest on the investment included. Although these items may add substantially to the cost of owning and operating an automobile in some in- stances, the wide variance in their applica- tion among motorists makes it impractical to include them in this study.

Relation of Cost Elements

It is somewhat surprising to note that the several factors entering into the cost of operating the vehicle tend to keep the cost per mile within the rather narrow range of 7.35 cents in the first year to 5.24 cents’ in the tenth year. The high depreci- ation and insurance costs of the first few years are offset to a considerable degree by greater mileage and low maintenance costs, and by absence of tire replacement expendi- tures. Although the estimate is based on the assumption that the vehicle will be scrapped after 10 years of use, the proba- bility is, in a period in which there is a relative shortage of vehicles, that it would pass into the hands of a marginal user and continue in service. It is not likely, how- ever, that the over-all cost per mile would

2° These costs are all based on mid-1950 price levels. Practically all items of cost, with the exception of taxes, have increased since that time.

COST OF LIVING

AUTOMOBILES

"Ved to be reasonable, they are not pur- UNIT COST OF MAINTENANCE

ailable in sufficient coverage. The es- ) UNIT COST OF CONSTRUCTION

4o 60 80 100 PERCENT

Figure 2.—Relative increases in unit costs of selected items, 1940-50.

i59

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June 1951 e PUBLIC RO

160

appreciably reduced, provided the ve- e was maintained at a level to assure nimum safety and comfort.

Of the 7.35 cents-per-mile total operating sts in the first year of the estimate, the st of gasoline, including all taxes, was '4 cents per mile, Gasoline taxes iounted to only 0.433 cent per mile, or

67 cent per mile for each cent of the tax te. Thus each increment of 1 cent of x adds less than 1 percent to the total 3t of operating the vehicle. Under these

) cumstances it can be understood why no x increase has ever made a measurable ference in, the highway use of gasoline. There is good reason to believe that the erage motorist does not understand the ae relation between his vehicle ownership d operation costs and the tax monies ex-

)ynded for the highways he uses. It would obably come as a surprise to him to learn

) at the total amount he pays in highway- er taxes, toward the construction and aintenance of the roads over which his (tomobile is operated, is substantially ex- eded by all of the other major items of hicle operation cost. This fact is pre- nted graphically in figure 3.

| Because of the widely quoted statements ade in organized opposition to proposed creases in gasoline taxes in several States, ost automobile owners might be reluctant believe that each cent of the gasoline tax

‘counts for only 1 percent of total vehicle

erating costs. The average motorist also probably not aware that highway aprovements made possible by each addi-

onal cent of gasoline tax not only add to le safety and convenience of motor-vehicle

‘avel, but also reduce operating costs

trough improved surfaces, grades, and

mement, reduced mileage, and lessened

‘affic congestion.

j _ Highway Revenues and Needs

_ Although road-user tax rates have risen . 8s than any other automotive operating

rst during the past 10 years, the revenues tom them have increased substantially as a sult of the large increase in the number vehicles. The increases in highway con- A ietion and maintenance costs, however, ave so reduced the value of the highway oltar that total revenues today will pro-

de-only about the same number of units ae construction and maintenance that were urchased with 1940 revenues. While this “eduction in the purchasing power of rev- is undoubtedly the most serious single em now facing highway authorities, rere are two others of almost equal im- ortance—the mounting volume of traffic t which highway capacity must be pro-

ded, and the higher standards to which “oday’s highways must be constructed to

low safe travel for present speeds and us. If prices had remained at 1940 ls, current revenues would be adequate Maintain our then-existing system of

ILIC ROADS @ Vol. 26, No. 8

INSU 13.08% \

.GARAGING, PARKING, TOLLS, ETC. 13.60%

DEPRECIATION 21.16%

Figure 3.—Distribution of automobile ownership and operation costs.

roads and streets, and to improve and ex- pand the system as needed for the greatly increased number of vehicles. But with present revenues able to purchase only the amount of construction and maintenance that was purchased with 1940 revenues, highway authorities are finding it impossible to provide adequate highway capacity for a 5l-percent greater number of vehicles and a 60-percent increase in traffic volume.

Effect on the Individual

Discussions of road-user taxes are fre- quently of a technical nature not readily understood by the automobile owner. He is exposed to diametrically opposite views and irreconcilable statements. The allega- tion is made that “gasoline is cheap—only the tax is high.” Yet the price of gaso- line (excluding tax) now represents 19.8 percent of total automobile operating costs, while the gasoline tax is only 6.5 percent, and the tax portion of the total price of gasoline has decreased approximately 7 percent during the past decade. The motor- ist appears to be willing to pay tolls that cost the equivalent of an additional 15-cent tax per gallon for the use of controlled- access toll highways, but seems not to under-

stand the relatively low cost, per vehicle- mile, of adequate free highways. When automotive taxes and highway programs are discussed, he unfortunately sees figures only in large multiples of any amounts familiar to him. Being impressed by their magni- tude, he does not realize that the portion of these amounts that he pays as an individual is actually very small.

In most States there are certain minimum amounts that must be spent for highway administration, equipment, and mainte- nance. After these requirements have been met, any funds remaining are available for construction. Small increments in tax. allo- cations under these circumstances can amount to relatively large increases in funds available for construction. If the 19 States having gasoline tax rates of less than 5 cents per gallon were to increase their rates 1 cent, the State funds available for highway construction would be in- creased, on the average, by more than 40 percent. In over two-thirds of these States the construction funds would be increased an average of more than 50 percent. Yet this mcrease would cost the motorist (at 15 miles per gallon), only 0.067 cent per mile, or about 13 cents a week.

161

—_—_—“~

Volume Changes in Sand-Gravel Concrete

BY THE PHYSICAL RESEARCH BUREAU OF PUBLIC ROADS

Abnormal expansion, as evidenced in map- cracking. has been observed in concrete pavements built with sand-gravel aggregate in some midwestern States. Tests with this and two other aggregates of widely different mineral composition, combined with differ- ent types of cement and subjected to various weathering conditions, produced effects in the laboratory which correlated with those observed in the field.

Expansion of concrete specimens made with sand-gravel was much greater than that of similar specimens containing the other aggregates, and appeared to be due to some characteristic related to the mineral compo- sition of the sand-gravel. The magnitude of the expansion was markedly influenced by the properties of the cements used.

The addition of crushed limestone to the sand-gravel, producing a normally graded coarse aggregate which contained about 50 per cent calcareous material, eliminated the abnormal expansion entirely.

Introduction

BNORMAL EXPANSION of con-

4% crete pavement with resultant so-called “map-cracking” of the surface, which has been widely observed in certain midwestern states, particularly Kansas and Nebraska, prompted the Bureau of Public Roads about 10 years ago to initiate a series of tests to determine whether these effects could be reproduced in the laboratory and, if so, just what combinations of materials pro- duced them and what steps might be taken to eliminate the trouble. The tests in- volved the measurement of changes in length of concrete specimens containing aggregates from three sources: The Platte River in Ne- braska, Chicago, Ill., and Long Island, N. Y. The Platte River aggregate was repre- sentative of a class of materials locally known as “sand-gravel,’ which contains only a small percentage of particles larger than %g inch in size. Most of the concrete pavements in these areas which have shown distress were constructed with this type of aggregate. The aggregates from Long Island and the Chicago area were selected as representative of two sources differing widely in mineralogical composition but pos- sessing excellent service records in concrete.

162

BRANCH

Reported by F. H. JACKSON, Principal Engineer of Te and A. G. TIMMS, Senior Materials Engin:

Each of the three aggregates, in three

different gradations, was used in combina-’

tion with each of four cements. All of the latter met the usual American Society for Testing Materials requirements for type I cement, and two of them in addition met both the A.S.T.M. requirements for type II cement and the requirements of the Board of Water Supply of New York City.

The concrete specimens made from these aggregates and cements were sub- jected successively to various types of lab- oratory weathering cycles which involved alternate wetting and drying together with alternate heating and cooling, but without freezing and thawing. In general the pro- gram followed the pattern set by W. E. Gibson, of the Kansas State Highway Labo- ratory, who began studying this problem as early as 1932. The results of Gibson’s find- ings were reported before the Highway Re- search Board in 1988.*

A progress report giving the results of the studies made by the Bureau over a 2- year period was presented before the High- way Research Board in 1942.°. This was followed in 1949 by a final report which re- viewed the earlier work and gave the re- sults of further measurements up to a total of 9 years of exposure.’

In the report presented here the data and discussions of the latter two papers have been combined into a single report which is intended to serve as a complete and final report of this investigation as it was origi- nally planned.

Summary of Observations

The principal indications of these tests were as follows:

1. A laboratory weathering cycle which involved immersion in water at 70°F. for 24 hours followed by drying in air at 130°F. for 24 hours produced length changes and visual effects (such as map-cracking) in concrete test specimens that correlated with the behavior of similar concrete in the field.

2. Concrete specimens containing only the Platte River sand-gravel aggregate

1A study of map cracking in sand-gravel pavements, by W. E. Gibson. Proceedings of the Highway Re- search Board, Vol. 18, Part I, 1938, p. 227.

° Volume changes in sand-gravel concrete, by F. H. Jackson and W. F. Kellermann. Proceedings of the Highway Research Board, Vol. 22, 1942, p. 252.

8’ Volume changes in sand-gravel concrete, by F. H.

Jackson and A. G. Timms. Proceedings of the High- way Research Board, Vol. 29, 1949, p. 212.

<I Si

| |

developed, in general, much larger exp) sions than similar concrete containing | other two aggregates. In many cases | appearance of map-cracks on the surfe: of the specimens provided visual evide! of abnormal expansion. | 3. The abnormal expansion that de} oped when the Platte River sand-gravel * used as total aggregate appeared to be | to some characteristic related to its mini; composition rather than to its grading to the high cement content normally with this type of material. d 4, In the concrete specimens contair the Platte River sand-gravel as total ag gate, the magnitude of the expansions influenced to a marked degree by cer differences in the properties of the ° cements used. However, there was no lation observed in this study between amount of expansion and any of the p! ical or chemical properties of the ceme 5. Adding crushed limestone with an) imum size of 1% inches to the Platte R

A” a . % if toe F Mes be a! a !

Figure 1.—Typical map-cracking of gravel concrete pavement.

June 1951 e PUBLIC R

Table 1.—Chemical and physical properties of portland cements The sand-gravels vary somewhat in mineral i composition from place to place, but in

Potilendt orsant general they are composed of quartz and

—-~— = granitic materials with varying amounts of 1 2 3 4 feldspar and very little limestone or other es a caleareous material. i ie tp a te cs tat els ded 21.95 20.60 22.71 | . 28.16 The local sand-gravel deposits, widely eo eh A Moed > een BAS nC 8.57 Oe 4.72 5.11 distributed along the beds of such streams . Hime (C8O) eee eee 62.70 62.70 62.54 64.28 as the Arkansas and Kaw Rivers in Kansas MMAMP SIESTA VECO nix scree Aran SSE, Wet eitla te vip Suet os 9s p nile i i i Bieri gj] ER | EB | TH | Egg | and the Platte River in Nebraska, furnish Memes Oxi (NG sO) Mehta oe cyt: se cilcart the cic nu leis wind: .26 36 NES t y § rai i MepEotessium oxide (Ki0). 2.2... ee eee eee 67 56 3 oO Sey doe e op Bah egate aoe eRe ) Alkali calculated as Na20 oe 70 73 47 | "87 many parts of these States. These aggre- if} Water-soluble alkali calculated as Na,O.............. 52 .38 .18 21 ates in general are reasonably well graded i enputed ce ery ea areata 1 (percent) : & & y g Meetricalcium silicate (CiS) 2... le eee ee 42 38 39 / 38-inc é j aceSS meeoicalctum silicate (CxS)... eee Bed 32 31 36 35 oe ee pet ‘ eneEeD ‘ ve x pees | rene aluminate (CA) SE ane 9 16 | 5 | - of washing results in a deficiency in the etracalcium i it AE pea he ese re to | i i j § hee giltate (CaSOd.. ... seat: Oe, © hee 2.8 3.0 35 1 finer sand sizes, particularly in on Physical properties: | eri ssing the No. 50 sieve. The avail- _ Specific surface GWagner) ane ata eh « em. per gm..| 1,850 1,705 1,965 1,815 ! fee Ee & ike f q Sugar test (Merriman) : | | ability of these deposits makes them ex- CULTAL NDOT en nels SCHEME ml. . 33.2 36.8 eit De i acti . i Bemrcointle aye Wen. vse ms certeannes, ml... 48.1 57.5 2.7 27 ceedingly attractive from the economic muutoclave expansion, .............. 0.6205. percent. . 09 42 05 | 01 point of view, even though the fine grading Normal POMMSLENC Yn act, fens oe percent. . 24.5 Zo20 23 .5 24.0 ‘ : ; Tensile strength (1:3 mortar): | has in some cases necessitated the use of AV RRRE pa Ne wens ee oe). lb. per sq. in. . 305 340 | 315 360 i BPOR Giva mA sao; fo. ols... Ib. persq.in..| 875 420 ABN pe (486 cement contents as high as Tb rto G0 sais per cubic yard in order to meet require-

ments for design strength.

; The belief that these materials were of d-gravel, in the proportion of about 50 gravel.” Concrete in which it is used is satisfactory quality, and the fact that they ent by weight of the total aggregate, known as sand-gravel concrete to distingu- were so readily available, resulted in their iminated the abnormal expansion. This ish it from concrete containing normally use in the construction of a substantial ae true for all four of the cements in- graded coarse aggregate, which is called mileage of concrete pavements in Kansas Jaded in this investigation. locally “fine-and-coarse-aggregate” concrete. and Nebraska. For example, most of the |) 6. Concrete containing the sand and

ud avel from Long Island, an aggregate es- Table 2.—Grading, specific gravity, weight, and absorption of aggregates tially siliceous in character, developed

The compound compositions given are in “shorthand” form.

ter expansions than similar concrete mtaining the essentially calcareous sand Grading 8” id gravel from Chicago. This applied ane Seaton , te . 3 A i 1 ading : Aggregate ll three gradings in which these ma- epee ey eherore : Combined | S usec als were used and to all four cements. | Fi Cc aie ‘¢ ‘ ror | ine oarse Both the specimens containing a blend | : te he Platte River sand-gravel and crushed Grading: percentage retained on— | 3 ; stone and the specimens containing the ee Eee toate Ve chy ae aot ao gl ees ere i 55 36 ong Island sand and gravel, when used a ere Shy arth ee eee, ie 2 hk 2 fe in - *» . . . . . oO. BIS VS sree ahatanae g) tere at Sea Aho alsin Jae = | normal gradation in combination with Nae oinicvc nee Bor ee es 30 30 20 ee fe “ty 7 ‘ ‘ ING A116 SIeVersee peers «eas conde 55 50 49 (i two cements relatively high in com- MisiB0-ndvels husk ak a 80 65 60 100 es tricalcium aluminate, developed ING) Slew. ue car tants «ag. Wh el} 95 | 80 84 100 os ie * mee 3 INO. CLUOISICVe te emeE ee ae Petes aban ee 100 95 97 109 y ter expansions than similar specimens ne ans i JAS . i 3.75 SoD 3. +t 2.9 Mtaining the two cements having rela- Fineness modulus)... .......-.-.--> bei 3.75 | 3.35 aly i 5 Bulk specific gravity (dry): | 4 ey PrrecHiaces res os A Platte River. dy. ..a0 02.2.5 ' 2.61 2.61 2.61 LBSGW Pas « awpeets wever, this trend was not noted in the B-slongwalandteay teerk cb tena an coe | 2.65 2.66 arte pe a —Chi ee 2.62 Dy. 62 | 65 ens containing the sand and gravel RPG DICA RO a eave ge we eins 2 | ] Weight, dry rodded (lb. per cu. ft.) : Chicago. apc A—Platte River............. cel 116 122 118 | eas ee These tests indicate that aggregate B—Long Island........... ai, al 112 117 109 AVL fees ttt : * C—Chicago......... wae Lees 110 | ula 110 108 ae ‘acteristics other than size and grading, | ; : , Absorption (percent) : | = as particle shape, surface texture, par puion Mosca es 5 nyel qian he 0.32 0.27 aei7 dinate Ane eral composition, etc., will affect the BogLong Taland i603 ety" eae So | .29 | 28. 81 | 280 |i se lege ; ; C—Chicdgo..::.., Rea 2.34 1.98 | 1.69 | LAT DI|\< tem vetriraiae fount of cement necessary to maintain a sepeteig PEP vis NPN pe gear ake 8s eb eared oy et eed ae gate oe I ls ke ee - consistency, using a fixed water- 1 For this grading, where the Platte River combination was used, the materials include a combination of Platte River

nent ratio, to a much greater extent than aggregate, grading 1, and sufficient crushed limestone to give desired grading. $s been commonly assumed.

7 Use of Sand-Gravel

he lack of suitable deposits of coarse regate for concrete in many parts of isas and Nebraska, and in certain sec-

Table 3.—Other physical properties of aggregates

Aggregate | ai ane 6 A—Platte | B—Long C—Chicago |

ons of western Missouri and Iowa, has River sent 1a | 0 the extensive use of a naturally ! eS

ans . Soundness (sodium sulfate loss at 5 cycles) '........ ...percent. . 3.2 4.4 22 irring mixture of sand and fine gravel Resistance to abrasion (Los Angeles loss for grading D)’....... percent. . Abe / 265 247 | 1 ¢ ‘ Organic matter (color test).............. Pe net ek Sirti x: a { otal aggregate for concrete work in Mortar strength ratio, 7 days*.... Se i Ree ee ee LA oe .94 1.05 | .90

e regions. This material, substantially tg a PR es ce Pi ee eee eS

f which passes a 36-inch sieve, is known 1 Weighted average loss based on grading 1.

i <ba, ” ‘“ 2 A.S.T.M. standard C 131-39, tentative revision 1942.

lly as “mixed aggregate” or “sand- 3 ‘4_S.T-M. standard C 87-42.

163

LIC ROADS e Vol. 26, No. 8

1%- to 34-inch

Rock or mineral

34- to %-inch

Percentage composition for each sieve size indicated

3-inch to No. 4

No. 4 to No. 8

No. 8 to No. 16

Table 4.—Mineral analyses of aggregates

No. 16 to No. 30

A—Platte River aggregate: ranitiort > Pt Sole ch ale oe st cee ate vadee ony a

Quartets, crates «lo ake skne eee aes Sandstone. s.r bane aa te ee ea eee, 2 Ferruginous sandstones eh ns Make ee ee PRY OLItE A hilar saath noe Shah eaten atta ahicuatercueha aka EUDIGOSIUEy oe cae BG Rs meals oie ete eer Hornblende schists; sack. saeeeah cu eerie Andesitecc.: Cee reach ok oe ene ee Flornblendite ica Arete cece teks See Bobi tens, eens tite Stas ek i secs ee a ee aes B—Long Island aggregate: UAE LZ Soe cae he cree ce «ele ea heen haar are Ouarizite: 2. : sth. cee nea n eae we schistose ‘qQuartzite..to-cs a seit eae chee ae Hornblende:schist), 45..ce aac ca ieee eee GIGS DAN. art oh ese oh Chere armen ei terremee eres Rerruginoeus sandstone)». af aciete t ees Mica schist Pecan ae ae a oe here ieee cath enamels Granite: Saas oe eee be es CGHEISG tale, eee ithe aise. hie a cane DANGHEONG, Cte ba. SoM eS sitter ent See GeImet- schist tt. tit wart etnies cath marae acer: Biotest eRe ee Ee GL Ta Pear IMVISCOVITE. os,..cte Rok s ces URC ene Flornblendey \ 2 mates oe a. orale ciel ieee A Senicites, Afi aoe oe ee oe ee ee C—Chicago aggregate: Dolomite). ; S267 Cl sles we vs. 7 9 es Bogs beter eee a JULATTAItO emer: x naa ie oa trete cle wees bee ae ee PLEAD bt Pi 8 eich ratte cae eres. ots ae ee a an 7

Ghiprt ee. Bee Hee tees ae ad See te ee

59 19 8 3

Average compositio

No. 30 to | No. 50 to Passing _ FF No. 50 No. 100 No. 100 Gravel Sand | LOS. |etse Priarct als sere ees 55 7. 1b 4 3 22 18, 89 96 94 13.5 72, bh 3 1,5 ‘: EVA cen th cectse Pere eke aver nai eee TR ll atc et es oe - 1 |... 27 i 5 Sty hal 8 Lech cee Ta Re NS pcre ee Al Tie T°. bh ee BPE Ae a (eet? AP, N's T .. ee A das sateen: APO ogage lbkenor eae | SRR eae arm T nest wend. 4 ate, eit ete io treet Gh een ne T Ty? Vthe ae RSs Pode eae ene wy 95 96 98 77.3 92.10 Ae par (ee AY oe 12.6 2. Pi Aree RIA rye 1.3 is AN ORE alc Ih ee 3 x ROC ited ints Bh 8, a ‘ Sieve satan arse ae Ree 2.3) ).. ae SR ae ade hee se 2.3 ff rT. Bellin Baton eae eer eae 2 1 Sh Se RR ata | icles ROR A Deal ae 3 Af Raa coe CUR pipepe ee '~ oe | Sw aly basa vee log ane ea Tih: TR eS ee a ee | i hee (ere tal Pr tay es Se, ka" T Tse Sarsccacy seed oe eke | aoe eee | TT Pues ol ee eae £ 2 61 78 89.6 81.50 a Oe ere et oe 4.6 1) 1 1 a 3.6 i RS oe, (Ee Pen AE ace ee ele ee -6}. ae a dash acl] vtatemar aero ta See ee 3 Tl 24 34 Zoi Na. eet cae 14

i Gravel size considered as material retained on No. 4 sieve, sand as that passing No.

* Consists of quartz and feldspar with occasional biotite. ? This size Platte River aggregate not available. ‘ Trace.

original concrete pavement along U S 30 in Nebraska was of this type. This route follows the Platte River for many miles and the local sand-gravel is available at almost any point along the road with very short haul.

Unfortunately, the sand-gravel type of concrete pavement has not proved entirely satisfactory. Defects in the form of map- cracking of the surface frequently de- veloped on many sections within a few years. Sometimes these defects led to progressive failure of a type which eventually required repair or replacement of the affected areas. A survey of Nebraska pavements conducted in 1939 by the Bureau of Public Roads in cooperation with the State Department of Roads and Irrigation revealed that about one-third of the approximately 500 miles of sand-gravel concrete pavement surveyed, all of which was constructed between 1925 and 19385, had developed map-cracking of a type which appeared to be progressive. In contrast to these observations on sand- gravel concrete, no evidence of map-crack- ing had developed up to 1939 on any of the pavements laid with fine-and-coarse aggregate concrete.

Map-Cracking

Map-cracking as used in this report may be defined as the type which forms a pattern of irregularly shaped blocks in the surface of the concrete. Map-cracking per se is not necessarily serious; nor does it neces- sarily lead to disintegration or complete fail- ure. Some badly map-cracked pavements have proved durable under severe weather-

164

4 sieve.

ing conditions. However, when map-crack- ing is accompanied by other evidences of abnormal expansion, deep scaling, or un- soundness, as revealed by a lack of ring under the hammer, it can be generally as- sumed to be of the progressive type. An advanced stage of map-cracking of this type is shown in figure 1. Such a condition is evidence of disintegration even though under favorable conditions it may be pos- sible to maintain traffic over the road for many years without the necessity of making extensive repairs or replacements.

The fact that map-cracking sometimes develops on roads carrying comparatively light traffic would indicate that the funda- mental causes underlying the initial crack- ing are independent of this factor. The primary cause appears to be excessive and abnormal expansion of the concrete. Evi- dence of this is found in the closed expan- sion joints which usually accompany the appearance of map-cracking. Furthermore, this expansion seems to be confined to the sand-gravel concrete, being almost entirely absent on pavements containing the conven- tional fine-and-coarse aggregate type of concrete,

Object of the Investigation

One of the objects of this investigation was to determine whether the characteris- tic map-cracking which is frequently asso- ciated with the use of sand-gravel as total aggregate could be reproduced in the labo- ratory. As early as 1938 Gibson had shown that this type of failure could be developed in the laboratory by subjecting specimens

of concrete to alternations of heating ad cooling and wetting and drying without ° introduction of a freezing cycle. It ws) considered desirable to continue the line/f, attack suggested by Gibson by making series of tests which would include, in

4 dition to the Platte River aggregate, », ai f { |

; a |

terials from two other sources differig widely from it and from each other ® mineral composition. It was also const ered desirable to study the behavior of et crete containing these other materials wh graded exactly the same as the Platte Ri’ aggregate. In addition, the tests W planned to compare the behavior of ¢1 crete containing the Platte River matell with sufficient added crushed limestone) make a conventional total aggregate gral tion, with that of concrete of the sai proportions containing the other two agg: gates. Complete descriptions of the

terials, the mix data, and the weather cycles used in the study follow.

Cements and Aggregates

Thirty-six combinations of materials } volving four cements and three aggreg in each of three gradations were uaa these tests. The cements were chosent give a considerable range in chemical position, particularly with respect to } percentage of computed tricalcium alu nate (C:A). The results of physical té and chemical analyses of the cements given in table 1. Major differences in cements were as follows: ‘

June 1951 ¢ PUBLIC RO:

ment. 1.—A.S.T.M. type I, with 9 per- : tricaleium aluminate (C;A), low auto- ! expansion, high Merriman sugar-test 2, 0.70 percent total alkali, and 0.52 ent water-soluble alkali.

ment 2.—A.S.T.M. type I, with 16 per- tricalcium aluminate (C:A), relatively autoclave expansion, high sugar-test 2, 0.73 percent total alkali, and 0.38 ent water-soluble alkali.

ment 3.—A.S.T.M. type II, with 5 per- tricalcium aluminate (C:A), low sugar- value, low autoclave expansion, 0.47 ent total alkali, and 0.18 percent water- le alkali. Cement 3, in addition to ing the A.S.T.M. requirements, also the requirements of the New York City *d of Water Supply. It would there- be classified as a “Merriman” cement.‘ yment 4.—A.S.T.M. type II with 7 per- j tricalcium aluminate (C;A), low ).r-test value, low autoclave expansion, F percent total alkali, and 0.21 percent er-soluble alkali. Cement 4 was also sified as a Merriman cement.

will be observed from table 1 that ce- nit 2 has a considerably higher autoclave cinsion than the other three. It is also coarsest in terms of specific surface. }\ of interest that cements 2 and 3 were 4; the same mill, the former being the ilar commercial product and the latter ment modified to meet the requirements he New York Board of Water Supply. tshould be noted that this work was iated before the question of an alkali- regate reaction as possibly contributing jaap-cracking had been raised. For this son no attempt was made to secure wide ‘lations in the alkali contents of the four ‘ents.

he physical properties of the aggregates given in tables 2 and 3 and the mineral (position of the various size fractions in ile 4. All three of the aggregates met ‘conventional A.S.T.M. physical test re- rements for concrete aggregates. A eral description of the aggregates fol- 8:

lggregate A. — Sand-gravel from the tte River at Schuyler, Nebr., composed entially of granite, quartz, and feldspar, th about 0.3 percent material classified as i. The amount of feldspar, predomi- itly potash (orthoclase and microcline), ‘ied widely in the different sizes from a h of 40 percent in the No. 4-8 sieve size a low of 3 percent in the material pass- ‘the No. 100 sieve. This aggregate has, general, a poor service record,

lagregate B.—Sand and gravel from ng Island, N. Y., (the so-called ‘‘Cowe y material). The sand and gravel were dst entirely siliceous, being composed

The term “‘Merriman”’ cement is frequently used to he portland cement’that will meet the specifications Board of Water Supply of the City of New dition of 1937. These specifications, which con- Ttain special requirements not found in the . Specifications, were developed by the late ad Merriman, consulting engineer for the Board

years. Mr. Merriman felt that his special rements were necessary in order to insure proper , thereby insuring a more volume constant and durable product.

ROADS e Vol. 26, No. 8

Table 5.—Mix data’

Proportions by—

i Actual cement Net water con- Weight of fresh aggregate content (sacks tent (gal. per concrete Dry weight Absolute volume per cu. yd.) sack) (lb. per cu. ft.) SERIES I, GRADING 1 ee ee nae ea et Soe et ee ee 1-A 1:4.10 1:4.92 7.4 1-B 1:3.73 1:4.43 7.9 50 143 1-C 1:3.39 1:4.05 8.5 5.0 145 2-A 1:3.83 1:4.60 TA 5.0 142 2-B 1:3.15 1:3.74 8.7 5.0 140 2-C 1:2.98 1:3.56 932 5.0 143 3-A 1:4.01 1:4.82 7.6 5.0 144 3-B 1:83.44 1:4.08 8.3 5.0 142 3-C 1:3.30 1:3.94 8.6 5.0 145 4-A Anes 1:4.95 7.4 5.0 143 4-B 1:3.61 1:4.28 8.0 5.0 140 4-C 1:3.30 1:3.94 8.6 5.0 144 SERIES I, GRADING 2 1-A 1:4.04 1:4.86 gels 5.0 44 1-B 1:3.58 1:4.20 8.1 5.0 ii 1-C 1:3.10 1:3.70 9.0 5.0 145 2-A 1:3.62 1:4.35 8.1 5.0 143 2-B 1:3.02 1:3.59 9.0 5.0 140 2-C NEOs fil 1:3.24 9.8 5.0 143 3-A i ery 1:4.65 fos! 5.0 144 3-B 1:3.30 1:3.91 8.6 5.0 142 3-C Masigvedleg 1:3.79 8.9 5.0 145 4-A 1:4.13 1:4.96 1h 5.0 144 4-B 1:3.50 V34°15 See 5.0 140 4-C 1:2.93 1:3.49 9.3 5.0 143 SERIES II, GRADING 1? a 1-A 1:4.10 1347592) 7.4 5.0 142 1-B 1:4.10 1:4.86 fh-7- 5.8 140 1-C 1:4.10 1:4.89 ae 6.3 144 2-A 1:3.83 1:4.60 7.8 5.0 143 2-B 1:3.83 1:4.55 7.4 6.0 139 2-C 1:3.83 124.57 4.5 6.1 143 38-A 1:4.01 1:4.82 7.6 5.0 144 3-B 14.01 1:4.76 Wee 6.1 140 3-C 134.02 1:4.79 7.3 6.4 143 4—-A p Boe Bt I 1:4..95 7.3 5.0 141 4-B LA 12, 1:4.89 7.0 5.9 138 4-C a Be To 1:4.92 tO Gar 142 SERIES II, GRADING 2? 1-A 1:4.04 1:4.86 Too 5.0 144 1-B 1:4.04 1:4.80 ieee 6.0 140 1-C 1:4.04 1:4.83 eae 6.4 143 2-A 1:3.62 1:4.35 bhi! 5.0 143 2-B 1:3.62 14529 7.8 5.8 139 2-C 1:3.62 PAT B2 7.8 6.1 142 3-A 1:3.87 1:4.65 7.8 5.0 144 3-B 1:3.87 1:4.60 U4 5.9 140 3-C NS On 1:4.62 G5 Gal 143 4—A te ASS 1:4.96 7.4 5.0 143 4-B 1:4.13 1:4.90 7.0 6.1 138 4-C 1:4.13 1:4.93 hed: 6.4 142 SERIES I AND II, GRADING 3 1-A 1:2.53:4.49 1:3.04:5.43 5.1 Gz 152 1-B 1:2.43:4.49 1:2.86:5.37 Buk 6.0 151 1-C 1:2.438:4.49 132,02 20-0. a | 6.3 154 2-A 1:2.58:4.49 1:3.04:5.43 Brod 5.8 152 2-B 1:2.48:4.49 1:2-86:5.37 5.1 6.0 151 2-C 1:2.48:4.49 AWAD ARE Vasa ee W 5.1 6.6 153 3-A 1:2.58:4.49 1:3.04:5.43 bye | 6.1 152 3-B 1:2.438:4.49 1:2.86:5.37 5.1 6.0 152 3-C 1:2.438:4.49 1:2.92:5.31 6.1 | 6.5 153 A-A 1:2.53:4.49 1:3.04:5.43 5.1 5.8 152 4-B 1:2.48:4.49 12863 be04 5.1 6.0 150 4-C 1:2.48:4.49 132 (9225.32 5.1 | 6.5 152

1 Slump for gradings 1 and 2 in both series was approximately 1 inch; for grading 3, 2)4 inches. Fineness modulus was

3.75 for grading 1, 3.35 for grading 2, and 5.84 for grading 3.

2 In the case of aggregate A (Platte River) for Series II, the proportions and water content for each cement and grading are the same as was used for the corresponding combinations i in series I. In the case of aggregates B (Long Island) and C (Chicago), the proportions were the same as were used for the corresponding combinations involving aggregate A. The

water content was varied to maintain the desired slump.

of about 90 percent quartz and quartzite, with practically no feldspar. This aggre- gate has an excellent service record. Aggregate C.—Sand and gravel from Plainfield, Ill., in the Chicago area. In con- trast with aggregate B, it was almost en- tirely dolomitic in composition, the sand being about 80 percent and the gravel about 90 percent dolomitic material. About 15

percent of the sand was quartz. This ag- gregate also has an excellent service rec- ord,

Grading and Proportioning

Three different aggregate gradations were investigated. Sieve analyses of the various aggregates and aggregate combinations are

165

o eet ee

Figure 2.—Horizontal comparator with test specimen.

given in table 2. A summary of the grad- ings follows:

Grading 1.—The gradation of the Platte River sand-gravel as normally used: In reality a coarse sand, only 5 percent being retained on the %8-inch sieve and only 5 per- cent passing the No. 50 sieve.

Grading 2.—The same as grading 1 but with sufficient fines added (from the same source) to bring the total passing the No. 50 sieve up to 20 percent. The maximum size was not increased.

Grading 3.—A conventional aggregate gradation, from 1%-inch size down, with 64 percent retained on the No. 4 sieve. For

Table 6.—Cumulative changes in length’ after various storage periods

Test Series I: Percentage change in length after storage of —

aggregate A this was accomplished by add- ing crushed limestone (1%4-inch to %-inch

AFTER TEST[AXIS] 20.187 in

cal expansions.

Cement and aggregate 4 160 days | 360 days 660 days 2,450 days 3,270 days 160 days 360 days 660 days 2,450 days 3,270 (eyele A) | (eyele B) (eyele C) (eyele D) | (cycle E) (cycle A) (eycle B) (cycle C) (eyele D) (eyel GRADING 1 ; 1-A. , —0.005 0.001 1-B — .005 — .002 1-C —.017 —.010 2-A — .005 .008 2-B — .008 .002 2-C —.019 — .006 7% 3-A —.010 = OL ; a 3-B == 012 —.013 LOMO Nie cc Reweeetnt babs a2 aosnoeeeiste BPS cea = 3-C —.017 —OLZ iy 4-A —.010 —.005 = 2010: |.) ~ eh) 5) Oe 4-B —.016 —.011 z 4-C — .022 —.015 s GRADING 2 1-A —0.010 0 | 0.498 0.605 .607 —0.010 —0.006 0.646 0.720 0 i-B — .007 —0.004 .033 .072 .059 —.010 —.001 041 -042 bs 1 C —.018 —.015 O11 .026 0 —.019 —.011 .013 -019 ‘ 2-A. — .006 - 002 . 082 .098 .093 —.015 -001 «115 -148 2 B =.012 .003 . 033 .060 .039 —.014 - 002 . 030 .039 4 2-C —:022 —:010 018 041 010 —.021 —.006 022 036 é. 3-A —.013 — .017 . 030 .095 | .099 — .020 — .019 .144 .204 : 3-B — .020 —.017 .012 .057 | .045 —.017 — .006 .022 .033 . 3-C —.015 —.014 .010 .026 | .009 — .021 — .008 .010 .013 t 4-A / — .016 —.015 .008 . 038 -O1L — .015 —.014 .027 -041 4-B — .013 — .016 007 | .019 .008 —.019 —.010 .010 019 ' 4—( —.021 —.016 .003 .014 —.001 — .020 —.007 . 008 .013 33 GRADING 3 F 1-A.. —0.003 —0.001 0.022 0.042 / 0.033 —0.001 1-B —.004 — .004 . 062 187 | . 163 — .006 ‘ 1-C .004 - 002 .009 .024 | .016 —.012 7 2-A —.004 | 0 “012 ‘107 | “081 —.005 : 2-B 0 .004 024 | 072 | .078 —.007 ‘< 2-C — .007 — .005 .007 .043 | -014 — .018 : 3 . — .008 — .006 .005 -014 | .009 — .007 | 3-B —.010 — .003 -016 .030 | .023 — .012 : C —.013 —.001 -008 | sOa0 1 .016 —.015 = —.009 — .003 .004 -010 | . 007 — .009 i ae a oa — 006 001 039 046 | 033 —.013 4 Ea ahitg WES MLB e ie —'009 —:001 002 ‘013 | “007 — 1014 ¥

‘Each value is the average of_tests of two beams.

166

6x 6x20 in. i

r—0 in. goge line 74 sant fetid AFTER TEST [7 | »)

10 in. gage ine

Test Series IL: Percentage change in length after storage of—

——

in size) Pow Bethany Falls, Kans., te Platte River material (a procedure | lo. known as “sweetening”), resulting in a) bined aggregate consisting of 53 pet limestone and 47 percent sand-grave weight. For aggregates B and C thell aggregate was obtained by using gi from the same source as the sand, gradings being practically identical — that used for aggregate A combined the crushed limestone. q

Each of the four cements and three gregates was tested in each of the t gradations, making 36 combinations in Two series of tests were run and two s mens were cast for each combinatio each series, making a total of 144 spect in the entire program.

In test series I, for gradings 1 a the proportions were determined on

ORIGINAL BEAM BEFORE TE

2O'2 Sains

AFTER TEST[BOT 2016 "ine

. showing

June 1951 © PUBLIC R

ats, i

dure ging By gra C the ing Sand]

of an approximately constant slump 'a constant water-cement ratio of 0.67 70 ume (5.0 gallons per sack), for all Hoinations of cements and aggregates. [ esulted in average cement contents

bout 7.6 sacks per cubic yard for the tte River material, or about the same igh used in the roads which had given e. The corresponding cement factors ee B and C were considerably fier, averaging about 8.4 for aggregate 9.0 for aggregate C. For both grad- .@s 1 and 2 a slump of approximately 1 #1 was used, as this is the consistency ally employed in actual construction at -sand-gravel aggregate, test series II, for gradings 1 and 2 _, atical proportions (by weight) and con- i ‘ency were used for all three aggregates ‘Bi a given cement as were used in series vith that same cement and the Platte material (aggregate A). This was os purpose of equalizing somewhat _yariations in cement content which re- d from the use of a constant water- aent ratio in test series I. The resultant Hter-cement ratios in test series II varied lisiderably, running as high as 6.7 gal- 4s per sack as compared to the 5.0 gallons ack used in all mixes containing the fe River material. ing a grading 3 (the normal concrete grad- 3) in both test series I and II, the com- lations were proportioned on the basis an approximately constant cement factor 5 sacks per cubic yard, with the slump Juntained at approximately 2% inches. pit will be seen from the foregoing that, jt each variable involving aggregate A gradings 1 and 2, results based on four Jecimens of a kind (two in series I and n series II) were obtained as compared two specimens of a kind in the case of regates B and C. Thus, for aggre- é A, series II served as a check on series for grading 3, all of the data from ‘ries II served as a check on series I inas- as the same mixes were used for both. mplete mix data are given in table 5.

“FT

)

Mixing and Storage

Aggregates in gradings 1 and 2 and the vhe aggregate fraction of grading 3 con- d some free water at the time of mix- The coarse aggregates used in grad- ig © were in a saturated and surface-dry ndition at time of use. The necessary orrections for free water were made when Iiputing the net water-cement ratios. Xing was done in an open-pan Lancaster ixer, sufficient concrete for one 6 by 6 by Linch specimen being mixed at one time. */Me specimen for each of the three aggre- es, the three gradings, and two of the ur cements was made on each working Y, making 18 specimens per day, or a total 44 specimens in 8 working days. All cimens containing the 34-inch maximum P aggregate (gradings 1 and 2) were ided by thoroughly spading the concrete 1 a trowel, as it was found that the ndard rodding procedure was not satis-

. : } : ! f t | |

LIC ROADS e Vol. 26, No. 8

SERIES I 1.0 Fie] | AGGREGATE A roa

LENGTH CHANGE — PERCENT

SERIES II

CEMENT |

DAYS IN STORAGE (LOG,SCALE)

Figure 4.—Effect of aggregate type: Grading l.

factory for these mixtures. Specimens of normal concrete (grading 3) were molded by rodding in the standard manner. The consistency was not controlled directly by the use of the slump test but was judged by means of the flow test. The concrete mixes were adjusted to provide a consistency cor- responding to approximately a 1-inch slump for gradings 1 and 2 and a 2%-inch slump

for grading 3. All specimens were cured 1 day in the molds in the mixing room and 27 days in the moist room, prior to testing. After a preliminary moist storage period of 28 days, the concrete test beams were measured for length and then exposed suc- cessively to a series of cycles of heating and cooling and wetting and drying. As will be seen later, the pattern of cycles

167

was established during the course of the work, as need for change in procedure was evidenced. The complete series of cycles was as follows:

Cycle A.—One day in moist room at 70° F., followed by 1 day in air at 130° F., followed by 2 days in air at 70° F.: 40 cycles, requiring 160 days.

Cycle B.—One day in water at 70° F., followed by 1 day in air at 130° F., followed by 2 days in air at 70° F.: 50 cycles, re- quiring 200 days.

Cycle C.—One day in water at 70° F., followed by 1 day in air at 180° F.: 150 eycles, requiring 300 days.

Cycle D.—Continuous storage in moist air at 70° F. for 1,790 days (approximately 5 years).

Cycle E.—Exposure outdoors near Wash- ington, D. C., for 820 days (approximately 2% years), followed by 4 days resatura- tion in water.

Measurements

The test specimens used in this study were concrete beams 6 by 6 by 20 inches in size. Stainless steel plugs were set in the center of each end of the specimens and brass inserts, provided with drilled gage seats, were set in the upper and lower sur- faces. Three sets of length-change read- ings were taken—one on the end plugs and the others along the upper and lower sur- faces of the specimens. These latter meas- urements were made with a mechanical strain gage over a 10-inch gage length; the end measurements were made with a horizontal comparator reading to 0.0001- inch. The comparator is shown in figure 2. All measurements were taken with the concrete in a moist condition at 70° F. in order to eliminate insofar as possible dif- ferences due to variations in temperature and moisture conditions at the time of test.

In general the surface measurements showed the same trends as those taken along the central axis. However, the surface measurements, which were made with a mechanical strain gage over a gage length of 10 inches, were somewhat erratic. The end measurements were made with a hori- zontal comparator over the entire 20-inch length of the beam and were quite consis- tent. The individual discrepancies noted in the surface readings reveal the difficulty of securing consistent results with a mechan- ical strain gage, which involves the personal equation. With the horizontal comparator, on the other hand, very consistent results are obtainable because the personal equa- tion is absent.

Discussion of Observations

The surface measurements, though er- ratic, do indicate two definite trends, neither of which would have been revealed by end measurements. During cycle D (continuous moist storage for 1,790 days) the surface measurements revealed appreciable warping in many of the specimens, particularly those which had developed large residual expan-

168

SERIES I

AGGREGATE A

SERIES II CEMENT | oe

LENGTH CHANGE - PERCENT

CYCLE

DAYS IN STORAGE (LOG. SCALE )

Figure 5.—Effect of aggregate type: Grading 2.

sions at the end of cycle C. These were principally the combinations involving ag- gregate A (the Platte River material) in gradings 1 and 2. The over-all expansion of these specimens at the end of cycle D was also large. In other words, they con- tinued to expand after the wetting and drying cycle had been discontinued. Warping was revealed by substantially higher expansion along the top surface than along the lower surface. This caused the ends to curl downward, as illustrated in figure 3, which shows readings for one of the beams in the combination of aggregate A (in grading 1) with cement 1. These measurements no doubt reflected the tend- ency of the surface mortar to expand at a greater rate than the mass of the concrete. Such a tendency probably exists in most concrete pavements because, due to finishing operations, a layer of mortar of distinctly inferior quality is formed on the surface of the pavement. These length differen- tials between the upper and lower surfaces were found only in the combinations which

had expanded excessively. Where the all expansions were small (0.1 perce less), which was the case with the majcd of the combinations, the warping tend) was not indicated by the measurem

This was due, it is believed, to the fact 1 the surface measurements were not su

ently precise to reveal the very small ley changes involved.

Another interesting trend was the ward warping at the ends of most 0 specimens at the end of cycle E (ow storage on the ground for 2% years). ' warping was probably due to differem drying out of the top surface with res? to the lower surface, since the latter in contact with the ground. Here agi however, the individual results show n@ inconsistencies. Although the general tri indicated by the surface measurements probably bona fide, it is believed the dividual measurements, for the ree

SERIES..1

CEMENT 3

Biegate A in grading 3. For this reason Me: data are omitted and the balance of feport will be limited to a discussion of énd measurements only.

axes, at the expiration of the various sure periods, are given in table 6 and plotted in figures 4-7. Each value is fiverage of measurements on two speci- ‘ made on different days. In the case igeregate A in gradings 1 and 2, and ree aggregates in grading 3, the same ortions and consistency were used in test series I and II. In this case, ‘fore, the results of the two series are tly comparable, a point which should orne in mind when studying the data. he other hand, combinations involving egates B and C in gradings 1 and 2 are trictly comparable in the two series due 1e fact that a constant water-cement : was used in series I whereas in series e weight proportions were kept con- / for each cement. Even in these cases, er, reference to the data will show le differences in cement content and content, although quite large, were mtly not sufficiently great to affect eneral trends to an appreciable extent.

IC ROADS e Vol. 26, No. 8

SERIES I

CEMENT |

AGGREGAT 4

DAYS IN STORAGE (LOG, SCALE)

Figure 6.—Effect of aggregate type: Grading 3.

At the end of cycle A (160 days), it was found that all of the specimens were show- ing small residual contractions. This indi- cated quite definitely that 24 hours in the moist room was not long enough to insure complete resaturation after drying at 130° F. Cycle B was therefore introduced, to provide for immersion in water instead of storage in the moist room. After 50 alter- nations of cycle B, however, the net expan- sions were still found in all cases to be very small.

Cycle C was then instituted, omitting altogether the 48-hour storage period in air at 70°F. Under this procedure the speci- mens were immersed immediately in water upon removal from the drying oven at 130° F., thus simulating the effect of a sudden cool shower upon a concrete pavement at the close of a hot dry day. This treatment had the effect desired: It differentiated quite definitely between the concretes in a man- ner similar to that observed in service.

Cycle C was continued for 300 days. Ab- normal expansion (an increase in length of almost 1 percent in certain cases) had de- veloped in some of the Platte River sand- gravel combinations by that time, with re- sultant map-cracking and other evidences of deterioration. This indicated the desira- bility of discontinuing the type of cycle which involved daily handling of the speci-

mens. They were therefore stored in the moist room for approximately 5 years (cycle D), after which they were again measured for length and then stored out- doors on the ground in the vicinity of the laboratory (cycle E). The final set of readings was taken after about 244 years of storage outdoors, at which time the speci- mens were approximately 9 years old.

Effect of Aggregate in Grading 1

Figure 4 shows for grading 1 and for each cement the effect of aggregate type on length change. It will be seen that the various combinations involving aggregate A, all of which showed relatively high ex- pansion at the end of cycle C, continued to expand through cycle D and, in most cases, through cycle E. The concrete containing cement 2 is the only exception to the latter tendency. On the other hand, the con- cretes containing aggregates B and C, al- though showing small additional expansions at the end of cycle D, all contracted as the result of the outdoor exposure of cycle E. These facts would indicate that whatever the nature of the internal reactions which caused the excessive expansion with agegre- gate A, the same reactions were continuing through cycle E. Otherwise, contractions would be expected during cycle E similar to those shown in the case of aggregates B and C.

It should also be noted that the amount of the expansion occurring in the concrete containing aggregate A was influenced ap- preciably by the cement, cement 1 being by far the most active and cement 2 the least active of the four. When studying figure 4, it is important to remember that, insofar as aggregate A is concerned, the propor- tions used in series II were identical with those used in series I, although an interval of nearly a month elapsed between the cast- ing of the specimens in the two series. The similarity of the trends as revealed in the two series is quite striking and tends to show that the trends shown in series I were not accidental.

It should be observed, also, that the in- fluence of aggregate grading has been en- tirely eliminated by this grouping of the data since all of the specimens, regardless of aggregate type, contain material of iden- tical grading (in this case grading 1, the norma] grading of the Platte River ma- terial). The data show conclusively that aggregate grading is not responsible for the excessive expansions which have taken place.

As noted above, all of the concretes con- taining aggregates B and C expanded some- what during cycle D and then showed con- traction at the end of cycle E. Further- more, aggregate B, the siliceous material from Long Island, consistently showed high- er expansions than aggregate C, the dolo- mitic material from Chicago. There is a strong possibility that these differences, although small as compared to the expan- sions found in the case of aggregate A, may be related to differences in the thermal

169

AGGREGATE B

AGGREGATE ©

AGGREGATE A 0.11 CEMENT®# 2 \ 0.10 T | \| | C.09 | -+ T | | 0.08 _— 0.07 . 0,06 + ~— = = Gi QO 0,05 t = a CEMENT# j WwW a fe 1 w 0.04++—+—+ o | g / a x eo ODS lar Ae te oO CEMENT# 3 za lu Bly 40.G2 + 0.01 O | = O.0 ft 0,02 | (e) wo t+ N |

exe)

832 8§ oe JN

be Ns gr Se Nm

Fate BrleGal =D Vel PAIS Si Cielee Diet e] [ASB SipCul De et CYCLE CYCLE CYCLE

DAYS IN STORAGE (LOG. SCALE )

Figure 7.—Effect of cement:

characteristics of the two aggregates. However, there is no evidence of abnormal growth math either of these materials. The maximum. expansions with all but one cement were less than the 0.1 percent, which is frequently indicated as the dividing line between normal and abnormal behavior in this regard.

The reason for the abnormal expansions found with the Platte River material re- mains unknown. There is the possibility of a slight alkali-aggregate reaction, but the fact that the Platte River aggregate used in these tests contained only 0.3 percent opal, coupled with: the lack of relation be- tween the alkali contents of the four cements and the resultant volume change, would tend to minimize this possibility. Neither can these abnormal expansions be due to the rich mix that was used, because in series I the cement contents of the combinations involving aggregates B and C were actually

higher than those which involved ag- gregate A. 170

Grading 3 (average for tests series I and II).

There remains the possibility that these abnormal effects are due to differential thermal characteristics of the aggregates. Blanks°® has called attention to the fact that aggregate of the same general nature as the Platte River material contains sub- stantial amounts of the orthoclase and mi- crocline feldspars and that these minerals have a very low thermal coefficient of ex- pansion. The Platte River gravel used in these tests contained varying amounts of these minerals, ranging up to as much as 40 percent in the Nos. 4-8 sieve size. It is possible that the deterioration of concrete containing this material may be due, at least in part, to stress developed within the concrete as the result of thermal incom- patibility. This fact alone. however, would not account for the wide differences in ex- pansion noted with the different cements. These differences must be related to some

*° Modern concepts applied to concrete aggregate, by R. F. Blanks. Proceedings of the American Society of Civil Engineers, Vol. 75, No. 4, April 1949, p. 441.

characteristic or characteristics of the eoj/t! bination which are influenced by both thy, aggregate and the cement. Whether thi », effects are physical or chemical, or a bination of the two, has not been det mined.

Effect of Aggregate in Grading |

Figure 5 shows, for each cement, the | fect of aggregate type when used in gradi} . 2. This grading was the same as gradi} 1 except that sufficient fine material fr the same source was added to increase * total amount passing the No. 50 sieve fr| 5 percent to 20 percent, with no incre}, in the amount retained on the 36-inch sie

A comparison of figures 4 and 5 indicat} for cements 1 and 2, trends almost identi), in grading 2 with those found with gradi, 1. In the case of cement 1, the addition} fines, while causing some reduction, did ; Eereeinhic decrease the excessive expib sion shown by aggregate A in grading| - In the case of cement 2, about the same ‘ pansions were noted fdr both gradings, values being comparatively low in bf, cases. In the case of cement 3 in seriet and cement 4 in both series, the abnortil expansion shown for aggregate A in gr ing 1 was largely eliminated. In fact, far as cement 4 is concerned, the expansi found for all three aggregates were all within the 0.1-percent limit previously m tioned. In other words, for this cemeh™ as well as for cement 3 in series I, conerg@ containing the Platte River material grading 2 behaved normally. |

In general it may be said that the acis’ tion of fines to the Platte River maten reduced the expansions somewhat, amount of the reduction varying with | cement. Moreover, the tendency for ci tinued expansion with cements 1, 3, ani@ during cycle E, noted in the case of gradig’ 1, was not found with grading 2.

Attention has been called to the fact thi in series I, the cement contents of the crete containing aggregates B and C wig substantially higher than those used wi y aggregate A. For example, in the case aggregate C in grading 2, cement 2 of ser e® I (fig. 5), the cement factor was 9.8 sa@

per cubic yard as compared to 9.0 for u

gregate B and 8.1 for aggregate A. Thi values, as well as the corresponding cem

factors for the other combinations used! i series I, gradings 1 or 2, are shown | ; table 5. The variations were necessary@ order to maintain the same water-cem} ratio throughout the series. The datas definitely that there is no relation whate} between cement content and expansion. | fact, as will be seen later, the actual exp} sions of certain combinations in grading / and 2, all of which involved the use of v rich mixes in series I, were no higher} any time than the expansions develo} with grading 3 (the normal concret where the cement content was reduced t ; sacks per cubic yard.

hin

5 fl

pal

{ ¥ ‘ H

PEO the ody

~ “2

June 1951 © PUBLIC RF

fect of Aggregate in Grading 3 he effect of aggregate type in grading 3 t each cement is shown in figure 6. It be noted that in practically all cases abnormal expansions which occurred n using aggregate A in gradings 1 and ere eliminated by the use of a normal ‘rete grading obtained by mixing the tte River material with crushed lime- e. In fact, the maximum expansions 1 this combination were actually less in cases, except with cement 2, than were ie for the corresponding combinations ving aggregate B. In studying figure /should be borne in mind that aggregate the Platte River sand-gravel, has been bined with crushed limestone in about il proportions. This substantially re- ed the silica content of the aggregate, ch may account for the smaller expan- is found in the case of aggregate A as pared to aggregate B, which was almost rely siliceous. In the case of cement 2, 1 series show higher expansions for ag- gate A than for either B or C. This arsal cannot be considered accidental te the results of the two series check h other almost exactly.

Effect of Cement in Grading 3

Ixcept for the combination involving ient 1 and aggregate B, virtually all of f expansions observed in the normal crete (grading 3) were within the ge of 0 to 0.1 percent. It was de- ad, therefore, to plot the length changes this grading on a very much larger tical scale than that used in figures 4-6. igure 7, the chart so produced, differences expansion of the order of 0.01 percent or ; are clearly indicated and may be of le interest. Each point used in plotting “curves was the average of four deter- lations—two in series I and two in series | The corresponding length changes for h series separately are shown in table 6. n studying figure 7, the nature of the ous exposure cycles should be kept arly in mind. It will be recalled that le A involved a 72-hour drying period lowed by 24 hours in moist air. Figure hows clearly that 24 hours of resatura- nin moist air was not sufficient to prevent idual contraction. Furthermore, there med to be a definite tendency for cements ind 4 to show greater contractions than nents 1 and 2 (except the aggregate C- nent 2 combination), this trend being evi- in the case of all three aggregates in h series. Also, for a given cement, con- tte containing aggregate C showed some- greater contraction than the concretes Which aggregates A and B were used. ‘the conclusion of cycle A the moist stor- ondition was changed to 24 hours in instead of in moist air, the period of ying remaining the same. At the expira- n of 50 cycles of this treatment (cycle B), the specimens had expanded, although ost cases they still showed some residual atraction.

, |

: LIC ROADS e Vol. 26. No. &

Figure 8.—Abnormal expansion of specimens containing sand-gravel aggregate: (op) grading 1 with cement 1, at end of cycle C; (center) grading 2 with cement 1, at end of cycle E; (bottom) grading I with cement 3, at end of eycle E.

With the elimination of the 48-hour dry- ing period at 70°F. (cycle C), the specimens continued to expand, this trend continuing through cycle D. It will be noted that at the expiration of cycle C all combinations showed residual expansion, the amounts varying with both the cement and the ag- gregate. Cements 1 and 2 expanded more than cements 38 and 4, the difference being much more marked in the case of aggre- gates A and B than in the case of aggre- grate C.

In most cases the specimens contracted during cycle E. After 2% years of outdoor exposure, the 96 hours in water which was provided at the end of cycle E was ap- parently not sufficient to resaturate the specimens. In the case of cement 2 with aggregate B, readings at the end of cycle E showed further expansion, which is a defi- nite exception to the general trend. How- ever, it should be noted again that the same tendency was found in_ both series (see fig. 6).

The chief point of interest observable in figure 7 is the relatively high expansion which took place in the combinations in- volving cements 1 and 2 with aggregates AandB. Aggregate A in this grading was

composed of a mixture of the Platte River material and crushed limestone in about equal parts; aggregate B was almost 100 percent quartz or quartzite; and aggregate C about 95 percent dolomite. The chief difference in the cements is the fact that cements 3 and 4, in addition to meeting the standard A.S.T.M. requirements, also met the specification requirements of the New York City Board of Water Supply.

Cement meeting these requirements would be classified as A.S.T.M. type II, principally because of the limitation on alumina, but they are much more restrictive than type II in that they also include limitations on sugar solubility (a test devised by Merri- man to detect underburning) as well as a requirement on maximum allowable water- soluble alkali. The authors are not pre- pared to advance an explanation for the increase in expansion noted in the case of cements 1 and 2 in combination with ag- gregates A and B as compared to the ex- pansion noted for other combinations. How- ever, the trends are so definite and are re- peated so consistently in the two series of tests as to make it extremely unlikely that they are accidental. The data are pre- sented as an interesting example of the

171

ag lh thesis heaahensit

possible variations in the volume change characteristics of different combinations of cements and aggregates. They illustrate a principle which is being recognized more and more: The volume constancy of con- crete is influenced to a marked degree by the particular combination of cement and aggregates used in the mix, and these ma- terials must be studied in combination with each other in concrete rather than indi- vidually.

Examples of the excessive map-cracking which developed in many of the specimens containing aggregate A are shown in fig. 8.

Unsolved Problems

It is realized that the foregoing discus- sions raise many questions for which an- swers have not been supplied. This is just as true now as it was in 1942 when the

A FACTUAL DISCUSSION OF MOTOR- TRUCK OPERATION, REGULATION, AND TAXATION

The Bureau of Public Roads has recently published A Factual Discussion of Motor- truck Operation, Regulation, and Taxation, a 113-page bulletin presenting in summary form the factual records and other data available to the Bureau, with discussions of their significance, which might prove useful in any study and investigation of the trans- portation problem. The bulletin may be purchased from the Superintendent of Docu-

original progress report was prepared, For example, no one, as far as the authors are aware, has yet advanced an entirely satis- factory explanation for the abnormal ex- pansion which takes place when Platte River or similar aggregate is used in con- crete with certain cements. Nor has an adequate explanation been forthcoming as to why this expansion can be stopped by the addition of crushed limestone to such aggregates.

These tests, as well as tests made by other investigators, have proved that con- ventional factors such as aggregate grad- ing, aggregate quality as measured by con- ventional tests, cement content, free lime in cement, etc., are not sufficient to explain this abnormal expansion. The probability that the aggregate is mildly alkali-reactive, combined with the fact that from one-fourth to one-third of the aggregate consists of a

New Publication

ments, U. S.. Government Printing Office, Washington 25, D. C., at 30 cents a copy. The subject material in the bulletin is presented in seven parts, covering the growth of motor-vehicle registration and use, the effects of size and weight of ve- hicles on the geometric design and traffic capacity of highways, axle loading and its effect on roads and legal limitation, weight of vehicles and its effect on bridges, the character of overloaded vehicles and their pay loads, highway-user tax payments in relation to highway revenues and expendi- tures, and the allocation of highway tax

Highway Soil Enéimeering

Highway Soi Engineering, a motion pic- ture produced by the Bureau of Public Roads to illustrate field surveying and sampling and laboratory testing of soils encountered in highway construction, is now available on loan to highway departments, universities, and other organizations. The 16-millimeter film, with sound and in full color, has a running time of almost two hours. The subject treatment is technical in nature and of interest primarily to engi- neers and engineering students.

Highway Soil Engineering describes the

172

two distinctive components of soil—granu- lar and silt-clay materials—and illustrates the methods employed in surveying and sampling soils in the field. Laboratory tests are presented in sequences which show the step-by-step procedures involved. The tests demonstrated are those used by the Bureau and many of the State highway departments, and cover the complete range needed to examine the properties of soils that are of interest to highway engineers.

The picture shows the striking contrast in condition and in maintenance require-

U.S, GOVERNMENT PRINTING OFFICE: 1951-91133!

type of feldspar having a low thermal efficient of expansion, may supply the swer, but the data of these tests indie quite definitely that neither of these fi taken separately is the answer. Moreo the fact that the Platte River aggres used in these tests contained only 0.8 ] cent opal, and insignificant amounts } other possibly reactive aggregates, we indicate that the alkali-aggregate react as it is generally considered, was not important factor. |

It is also difficult to visualize the mech) ics of an action which results in expans) due to the use of aggregate having a ® thermal coefficient of expansion. Howe’ there is also the possibility that the fe; par may contribute to the expansion in sig other way, due possibly to alteration, v, time, of its physical properties. a |

responsibility. Several appendixes con ing valuable information are also incluc!

The report was prepared at the requ of the Subcommittee on Domestic Land ¢ Water Transportation of the Committee) Interstate and Foreign Commerce, Uni} States Senate, which was investigating pr! lems relating to the transportation and « munications industries. The report ¥ presented before the committee in Ji 1950 and is reprinted from the committe hearings, which appeared under the t Study of Domestic Land and Water Tra

portation. j

Film

ments of pavements laid on good and poor subgrade soils. It concludes with demonstration of the value of a sand s base in preventing intrusion of subgrade s into the overlying crushed-stone base cour:

Highway Soil Engineering may be bi rowed by any responsible organization wi out cost, except for the nominal transpo tion charges. The film may be obtain for showings by writing to the Visual Ee cation Branch, Bureau of Public Roa Washington 25, D. C.

A A complete list of the publications of the \ | Bureau of Public Roads, classified according to subject and including the more important articles in PUBLIC ROADS, may be obtained upon ®@)request addressed to Bureau of Public Roads. Washington 25, D. C.

The following publications are sold by the Superintendent ‘of Documents, Government Printing Office, Washington 25, (Dp. C. Orders should be sent direct to the Superintendent of Documents. Prepayment is required.

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/ Annual Report, Bureau of Public Roads, 1950.

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Road Work on Farm Outlets Needs Skill and Right Equipment.

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