Tech. Note TN-1747 — Feb IG Se ONG February 1986 \ By AP Smith Sponsored By Naval Facilities Technical Note Engineering Command UNDERWATER NONDESTRUCTIVE TESTING OF CONCRETE: AN EVALUATION OF TECHNIQUES ABSTRACT Three commericially available instruments for testing concrete above water were successfully modified for underwater use and evaluated in laboratory and field tests. One instrument was a magnetic rebar locator that locates rebar in concrete structures and measures the amount of concrete cover over the rebar. Another instrument was a Schmidt hammer that evaluates the surface hardness of the concrete and obtains a general/condition assessment. The third instrument was ultrasonic test equipment that estimates compressive strength, detects cracks, and provides a general condition rating of the concrete based on sound velocity measurements. Laboratory and field tests did not reveal any problems with the fundamental operation of each instrument after they were modified. 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REPORT NUMBER 2. GOVT ACCESSION NO.| 3. RECIPIENT'S CATALOG NUMBER TN-1747 DN987077 4. TITLE (and Subtitle) 5. TYPE OF REPORT & PERIOD COVERED UNDERWATER NONDESTRUCTIVE TESTING OF Interim: Oct 1983 — Sep 1984 CONCRETE: AN EVALUATION OF TECHNIQUES 6 PERFORMING ORG. REPORT NUMBER 7. AUTHOR(s) 8. CONTRACT OR GRANT NUMBER(s) A. P. Smith 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT, TASK NAVAL CIVIL ENGINEERING LABORATORY oS aCe SEL LE Orr aca Port H California 93043 Saeey ‘ort Hueneme, California YO995-01-004-310A 11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE Naval Facilities Engineering Command February 1986 Alexandria, Virginia 22332 2, ae CASES - MONITORING AGENCY NAME & ADORESS(if different from Controlling Office) 15. SECURITY CLASS. (of this report) Unclassified 15a, DECLASSIFICATION’ DOWNGRADING SCHEDULE 16. DISTRIBUTION STATEMENT (of this Report) Approved for public release; distribution unlimited. . DISTRIBUTION STATEMENT (of the abstract entered in Block 20, if different from Report) 18. SUPPLEMENTARY NOTES . KEY WORDS (Continue on reverse side if necessary and identify by block number) Underwater inspection, nondestructive testing, waterfront facilities, concrete, Schmidt hammer, rebar location, ultrasonic testing 20. ABSTRACT (Continue on reverse side if necessary and identify by block number) Three commercially available instruments for testing concrete above water were successfully modified for underwater use and evaluated in laboratory and field tests. One of the three instruments was a magnetic rebar locator that locates rebar in concrete struc- tures and measures the amount of concrete cover over the rebar. Another instrument was a Schmidt hammer that evaluates the surface hardness of the concrete and obtains a general continued FORM ae DD , jan 73 1473 EDITION OF 1 Nov 65 Is OBSOLETE Unclassified SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) CT 0 830 Unclassified SECURITY CLASSIFICATION OF THIS PAGE(When Data Entered) 20. Continued condition assessment. The third instrument evaluated was ultrasonic test equipment that estimates compressive strength, detects cracks, and provides a general condition rating of the concrete based on sound velocity measurements. Laboratory and field tests did not reveal any problems with the fundamental opera- tion of each instrument after they were modified. There was a 23% shift in the output data for the Schmidt hammer as a result of the modifications, but this shift can be elimina- ted by designing it for underwater use. The modifications did not affect the data from the other two instruments, and all of the instruments were easily operated by a diver. Library Card a Naval Civil Engineering Laboratory UNDERWATER NONDESTRUCTIVE TESTING OF CONCRETE: AN EVALUATION OF TECHNIQUES, by A. P. Smith TN-1747 64 pp illus February 1986 Unclassified 1. Underwater inspection 2. Nondestructive testing I. YO995-01-004-310A Three commercially available instruments for testing concrete above water were successfully modified for underwater use and evaluated in laboratory and field tests. One of the three instru- ments was a magnetic rebar locator that locates rebar in concrete structures and measures the amount of concrete cover over the rebar. Another instrument was a Schmidt hammer that evalu- ates the surface hardness of the concrete and obtains a general condition assessment. The third instrument evaluated was ultrasonic test equipment that estimates compressive strength, detects cracks, and provides a general condition rating of the concrete based on sound velocity measure- ments. Laboratory and field tests did not reveal any problems with the fundamental operations of each instrument after they were modified. There was a 23% shift in the output data for the Schmid hammer as a result of the modifications, but this shift can be eliminated by designing it for under- water use. The modifications did not affect the data from the other two instruments, and all of the instruments were easily operated by a diver. — Ce Ce ee eee CC CC Unclassified — SECURITY CLASSIFICATION OF THIS PAGE/When Data Entered) EXECUTIVE SUMMARY Three commercially available instruments for testing concrete above water were successfully modified for underwater use and evaluated in laboratory and field tests. Each instrument represents a different tech- nique for evaluating concrete structures. Instruments for the following methods were tested: a. A magnetic rebar locator that can be used to locate rebar in concrete structures and measure the amount of concrete cover over the rebar. b. A Schmidt hammer that can be used to evaluate the surface hard- ness of the concrete and obtain a general condition assessment. c. Ultrasonic test equipment that can be used to estimate compressive strength, detect cracks, and provide a general condition rating of the concrete, based on sound velocity measurements. Laboratory and field tests did not reveal any problems with the fundamental operation of each instrument. Only the Schmidt hammer showed a shift in output data (23%) as a result of the modifications. This shift can be eliminated by modifying the design. Modification for under- water operation did not affect data from the other two instruments, and all instruments were easily operated by a diver. 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NERDS 6 6 60000 oO OOo APPENDIX - Nominal Dimensions of Reinforcing vii Steel vrai ' ait re a a oe Tey ae tl # andnsddat % mi | i ; sesame este | + sia 4 - aiw } Tae INTRODUCTION Concrete is the most common construction material used by the Navy in waterfront structures. It is estimated that more than 40% of Navy piers consist of a concrete deck supported by concrete piles (Ref 1). In addition, concrete is also used extensively for retaining walls, encasement of other materials such as steel piles, and pavement. To adequately maintain these structures, periodic inspections are required, both above and below water. Currently, underwater inspections of concrete structures are con- ducted visually to assess the condition of the facility. The qualitative data obtained from these inspections are generally inadequate to accur- ately assess the condition of the structure. New techniques and equip- ment are required to provide more quantitative data from underwater inspections of concrete structures. The Naval Civil Engineering Laboratory (NCEL), under the sponsorship of the Naval Facilities Engineering Command (NAVFAC), has initiated a project to assess potential techniques for nondestructive testing (NDT) of concrete underwater. This report presents the results of laboratory and field evaluations of the Schmidt hammer, magnetic rebar locator, and ultrasonic testing equipment, all of which were modified for underwater use. BACKGROUND Many techniques for testing concrete above water have been developed and generally are well documented in the literature. Most of these tech- NMiques are discussed in Reference 2, published by the American Concrete Institute, which provides a good summary of nondestructive methods of testing concrete on land. Those techniques most easily adapted for inspecting concrete structures underwater have been identified and are listed below (Ref 3). e Magnetic Rebar Location - Magnetic rebar location devices detect the distortion in a magnetic flux field caused by the pressence of metallic rebar. e Rebound Method - The compressive strength of the concrete is corre- lated with the rebound height of a spring driven mass after impact. e Ultrasonic Testing - The transit time of high frequency sound waves is used to assess the condition of the concrete and detect internal defects. e Radiographic Tomography - The absorption and scatter of radiation is used to produce a visual image of the concrete cross section at the point of inspection, indicating the thickness and density. e Surface Hardness - The compressive strength of the concrete is correlated with the size of an indentation produced by a mass impacting the surface. e Penetration Techniques - The compressive strength of concrete is correlated with the depth of penetration of a hardened probe that is explosively fired into the concrete surface. e Pullout Testing Techniques - The compressive strength of concrete is correlated with the force required to pullout an anchor rod embedded in the surface of the concrete. (This is a destructive test and not desirable for underwater inspections because of the probability of exposing rebar.) e Coring - This is the standard technique for determining the quality and strength of concrete. Underwater coring equipment has been developed and is available. Generally, coring should only be considered when other inspection techniques indicate that a serious problem exists. The first four of these techniques were identified as offering the greatest potential to improve the Navy's ability to inspect concrete structures underwater (Ref 4). This report presents the results of laboratory and field evaluations of selected equipment that use the first three techniques: Technique Commercial Name Magnetic Rebar Location R-Meter Rebound Method Schmidt Hammer Ultrasonic Testing V-Meter The fourth technique, radiographic tomography, is not included in the report. However, a feasibility analysis and conceptual design of a tomography system to inspect concrete and timber have been completed and are described in References 5, 6, and 7. CONCRETE DETERIORATION AND INSPECTION REQUIREMENTS The most common damage resulting in the premature deterioration of concrete structures in or near seawater is cracking and loss of material or cross section. Softening of the concrete due to chemical action is another form of damage less common than cracking. The damage to concrete is generally most severe in the splash and tidal zones. Damage from corrosion of the steel reinforcement occurs when the corrosion products cause the volume of the structural element to expand, resulting in tensile stresses and cracking. As corrosion progresses, the corrosion products continue to expand, causing more cracking. Eventually, spalling occurs, exposing the steel reinforcement. Rust stains on the concrete surface are usually the first visual indication of corrosion of the reinforcement. Once these visual signs are evident, however, corrosion is well advanced, requiring costly repairs or replace- ment of the structure. Damage from overloading may occur due to ship impact or may be gener- ated by excessive pile driving forces during construction. The initial damage may be only hairline cracks that go unnoticed. Subsequent inter- mittent wetting may initiate corrosion of the reinforcement, causing the cracks to increase in number and size, leading eventually to spalling. Also, damage to concrete elements caused by freezing and thawing involves penetration of the water into small cracks which are then expanded and propagated by the forces generated when the water freezes. The common causes of damage to concrete are summarized below: Chemical Mechanical Corrosion of Reinforcement Accidental Overload Sulfate Attack Abrasion Chemical Reaction of Aggregates Freeze-Thaw Inspection data and accuracy requirements were established for the underwater inspection of concrete structures (Ref 1). Equipment and inspection techniques are required that can detect the presence and location of cracks greater than 1/32-inch wide, diameter of rebar to within 4% of the original diameter, concrete strength to within 12% of the mean strength of the entire element, and location of rebar and depth of concrete cover to within 1/4 inch. These data and accuracy require- ments were derived from structural analysis criteria. Three types of inspection are distinguishable by the resources and preparation needed to do the work and the type of damage or defect that is detectable (Ref 1). Therefore, the type of damage detected depends upon the level of inspection described below. e Level I - General Visual Inspection. This type of inspection does not involve cleaning any structural elements and can be conducted more rapidly than the other types of inspection. e Level II - Close-Up Visual Inspection. This type of inspection generally involves cleaning of structural elements and normally is restricted to the critical areas of the structural element. e Level III - Nondestructive Testing. This type of inspection is conducted to detect hidden or incipient damage. Generally, the equipment and test procedures will be more sophisticated than either the Level I or Level II inspection. The evaluation test results presented in this report are for equip- ment that would be used to perform a Level III inspection on underwater concrete structures. Table 1 summarizes the purpose of each inspection and the type of damage that each level of inspection will detect. MAGNETIC REBAR LOCATION —- R-METER General Description and Operation Reinforcing bar location devices detect the disturbance in a magnetic flux field caused by the presence of magnetic material. The magnitude of this disturbance is used to determine the location and orientation of steel reinforcing bars in concrete and to measure the depth of concrete cover over the rebar. These instruments are commercially available for measuring the depth of concrete cover in dry environments. Rebar locator devices typically consist of a U-shaped magnetic core upon which two coils are mounted. A magnetic field is produced by apply- ing an alternating current to one coil and measuring the current induced in the other coil. The magnitude of the induced current is affected by both the diameter of the rebar and its distance from the coils. There- fore, if either of these parameters is known, the other can be determined. By scanning with the probe until a peak reading is obtained, the location of the rebar can also be determined. A maximum deflection of the meter needle will occur when the axes of the probe poles are parallel to and directly over the axis of a reinforcing bar, thus indicating orientation. An R-meter rebar locator (Model C-4956) was purchased and modified for underwater use and is shown in Figure 1. This instrument is powered by a rechargeable 12-volt, 4.5-amp-hour storage battery and will operate for about 10 hours between charges. To fully recharge the battery from a completely discharged state requires about 16 hours. A detailed opera- tions manual is supplied with the unit (Ref 8). The R-Meter is calibrated for rebar that varies from No. 3 to No. 16 in size. (Appendix A defines the nominal dimensions of reinforcing steel.) The R-Meter can be used to measure the depth of concrete cover over rebar in the range of 1/4 to 8 inches, or conversely, it can measure the diam- eter of the rebar. The actual value of concrete cover measured corre- sponds to the distance between the tips of the probe and the top of the reinforcing bar as illustrated in Figure 2. The best accuracy (+10%) is obtained for concrete cover less than 4 inches thick. To obtain maximum accuracy for concrete cover measurements when using the R-Meter, the meter zero must be set accurately and rechecked frequently. The meter zero will drift with the battery charge level and temperature variations. Figure 3 shows the effect of zero setting error on the measurement of concrete cover (Ref 8). Curve A represents the condition of thick concrete cover and smaller diameter rebar. For this situation, small zero offsets introduce significant errors in the measurement. Curve D represents the condition of very thin concrete cover and larger diameter rebar. For this situation, zero offset does not introduce any significant error in the measurement. Curves B and C represent other measurement conditions and indicate that this effect is more pronounced for increased concrete cover and smaller diameter rebar. The primary limitation that effects the operation of the R-Meter is the presence of other metallic objects in the vicinity of the rebar where the measurement is being made. For example, in heavily reinforced struc-— tures, the effect of nearby rebar cannot be eliminated and accurate depth readings are difficult or impossible. The effects of parallel l-inch diameter rebar, located 2 inches below the surface of the concrete, is shown in Figure 4 (Ref 8). Theoretically, if the separation of the axes of two parallel rebars is at least three times the thickness of the con- crete cover, this effect can be neglected. In routine measurements, if the meter needle drops to a value of one or less on the linear scale when the probe is between the two bars, the effect can be neglected. The presence of rebar perpendicular to the axis of the probe has much less effect on the measurement of concrete cover than that of paraliel rebar and in most instances it can be ignored. For example, if the probe is not positioned directly above the perpendicular rebar or the perpendicular rebar is located beneath the rebar under test, the effect is negligible. The operations manual provides guidance to reduce these limitations and improve the measurement accuracy. Modifications for Underwater Use The first attempt at modifying the R-Meter for underwater use con- sisted of placing the entire instrument in a waterproof housing, 12 inches in diameter and 6 inches deep. The probe was located directly below the readout inside the waterproof housing. The readout was visible through a clear acrylic top. Im order to operate the modified R-Meter underwater, it was necessary for the diver to use both hands to position the instru- ment. Once the R-Meter was positioned the diver had to manually log the data. This sequence of events was difficult to accomplish and inefficient. Consequently, this approach was dropped in favor of waterproofing only the test probe. The electronics were kept topside, where the data were automatically recorded. To evaluate the R-Meter underwater using the second approach, it was necessary to waterproof the test probe, provide a remote indicator to orient the diver while using the instrument, and increase the length of the interconnecting cable between the test probe and the readout that was kept topside. The modified R-Meter is shown in Figure 5, including a closeup of the test probe. To waterproof the test probe a thin layer of epoxy was deposited over the exposed metal tips. The remote indicator was a small voltmeter that duplicated the meter movement from the deck unit. The voltmeter was mounted in a PVC housing and attached to the test probe. The diver used this indicator to locate rebar and orient the probe when measuring the depth of concrete cover. The actual measurement of concrete cover was made topside; the diver did not log any readings. The housing also contained a pressure gauge to measure the water depth and a waterproof connector. An underwater electrical cable (180 feet long) connected the probe to the deck unit. Laboratory Test Results The modified R-Meter was tested in the laboratory to determine if the modifications had any effect on the output and to check its perfor- mance underwater. To evaluate the performance of the modified R-Meter, measurements were taken on four concrete test specimens, each containing a different size of rebar. The size of each test block was 6x6x18 inches and the rebar was located slightly off-center. Measurements were taken before the modifications were done, after they were completed, and with the modified probe submerged in water. Figure 6 shows the R-Meter and one of the test blocks. Table 2 presents the test data in terms of measured concrete cover before the modifications were made and after modification with the probe submerged in water. Figure 7 is a plot of data from the same tests with readings from the linearized scale used for comparison. The test results showed no significant change in output data after the probe was modified to operate underwater. The maximum deviation was +1/8 inch and indicated increased concrete cover. Since the epoxy coat- ing deposited over the probe tips did raise the probe above the surface of the concrete about 0.05 inches, it was expected that the instrument should indicate increased concrete cover. However, interpretation of the readout to better than 1/16 of an inch is not practical, especially for thicker coverage (>4 inches) where 1/8 of an inch is probably more realistic. A qualitative test was performed in the seawater test tank at NCEL to evaluate the performance of divers using the R-Meter. A concrete slab (4x4x0.67 feet) containing different lengths of No. 5 rebar was used as a test specimen. NCEL divers surveyed both sides of the slab with the R-Meter probe and marked the location of the rebar. The results of the evaluation showed that the modified R-Meter was very easy for the diver to use. Rebar with less than 4 inches of conerete cover was easily detected and accurately located. Rebar with concrete cover between 4 and 6 inches was more difficult to locate and rebar with concrete cover greater than 6 inches was very difficult to locate because of the small deflection on the remote readout. Also, parallel rebars were not distinguishable from one another when the con- erete cover was 4 inches and the rebar spacing was 6 inches. Measure- ments from the opposite side of the slab did detect the parallel rebars where the concrete cover was only 2 inches. In summary, the R-Meter can be used successfully underwater to inspect concrete structures and perform the following functions, within the basic limitations of the instrument: 1. Determine the location of rebar in concrete structures, both orientation (+10 degrees) and position (+1/2 inch). 2. Measure the depth of concrete cover over rebar for the range of 1/4 to 8 inches thick with an accuracy of about +10%. 3. Determine the size of standard rebar (No. 3 to No. 16) with an accuracy of +10% which is roughly equivalent to one standard rebar size. The operation of the modified R-Meter in the laboratory did not reveal any problems with the fundamental operation of the instrument and there was no effect on the output data after the modification. SCHMIDT HAMMER General Description and Operation The Schmidt hammer utilizes the rebound method for determining the compressive strength of concrete. This is accomplished by correlating the rebound height of a spring-driven mass after it impacts the surface of the concrete with the compressive strength of the concrete under test. A Schmidt hammer, Model RM 710, Type L, modified for underwater use, is shown in Figure 8. A cutaway view of the hammer, illustrating the internal mechanisms, is shown in Figure 9. The Schmidt hammer is principally a surface hardness tester. It consists of a spring-driven mass that slides on a guide bar within the tubular housing as shown in Figure 9. To carry out a test, the impact plunger is pressed strongly against the concrete surface under test. This releases the spring-loaded mass from its locked position causing an impact. The mass then rebounds, taking the rider with it along the guide scale. By pushing a button, the operator can hold the rider in position while the index is read to the nearest whole number. This value is referred to as the rebound number and can vary over the range of 10 - 100 with higher numbers indicating stronger concrete. It is recommended that a minimum of 12 readings be taken per test site and averaged after discarding the minimum and maximum values (Ref 9). A general calibration chart (provided by Soiltest, Inc., Evanston, Illinois) that relates the rebound number to cylinder compressive strength for the Model RM 710 Schmidt hammer is shown in Figure 10. The Schmidt hammer has numerous limitations that should be recognized when using this instrument to obtain surface hardness data. For example, the test results obtained with the hammer are effected by the following: 1. The surface of the concrete under test has an important effect on the accuracy of the test results. Higher rebound numbers were obtained from smoother surfaces and the scatter in the data was less. Minimizing the data scatter increases the confidence in the test results. Thus, underwater concrete surfaces must be thoroughly cleaned and smoothed with something like a carborundum stone before measurements are taken. 2. Surface and internal moisture conditions of the concrete will also affect the results. Saturated concrete tends to show rebound readings five points lower than when tested dry. This will affect the comparison of data taken above and below the waterline. 3. The type of coarse aggregate and cement significantly effects the correlation of the rebound numbers with actual compressive strength of the concrete under test. A calibration curve is required for each particular concrete mix to assure accuracy. This is not practical for most situations. 4. Size, shape, rigidity, and age of the concrete become important when testing small concrete samples or recently poured concrete. This should not be a concern for the underwater inspection application. Because of these limitations, which are discussed more fully in Reference 2, the estimation of concrete compressive strength obtained with a rebound hammer is accurate only to about +25%. This applies to conerete specimens cast, cured, and tested under identical conditions as those from which the calibration curves were established. Because of the lack of accurate calibration data correlating compressive strength with rebound numbers, the Schmidt hammer is primarily useful for checking surface hardness and uniformity of concrete. It can also be used to compare one concrete against another if they are assumed to be reasonably similar. Modifications for Underwater Use To use the Schmidt hammer underwater, it was necessary to place the hammer in a waterproof housing with an O-ring seal on the impact plunger shaft. This required extending the impact plunger approximately 4 inches. In order to eliminate the diver recording data manually, an electrical pickup was added to sense the position of the rebound rider. This allowed the diver to take measurements as rapidly as possible. A 150-foot-long cable was used to connect the electrical pickup to the data acquisition system on the surface. Figure 11 shows the Schmidt hammer modified for underwater use. Laboratory Test Results Laboratory tests were performed on the Schmidt hammer to evaluate its basic performance. The modified Schmidt hammer was tested to determine if the modifications had any effect on the output and to evaluate its basic performance underwater. Test results obtained with the modified hammer were compared against the test data obtained with a standard Schmidt hammer. The basic Schmidt hammer calibration was checked using a test anvil provided by the manufacturer. The anvil is made of hardened steel and forms a surface upon which a reference reading can be obtained to check the calibration of the rebound hammer. Internal adjustments can be made in the Schmidt hammer to make small variations in the output to match the anvil reference reading. The range of this adjustment is about +4 points. Before modifying the Schmidt hammer, tests were conducted in a dry enviroment using the test anvil to evaluate the performance of the hammer and establish the repeatibility of the measurement. The rebound numbers for three different unmodified Schmidt hammers averaged 60 with a standard deviation less than 2.0. This agreed exactly with the reference rebound number on the test anvil. After the Schmidt hammer was modified for underwater use, the average rebound number, obtained using the test anvil in a dry enviroment, dropped to 46.5, although the standard deviation remained about the same. This represented a decrease in the standard reference rebound number for the modified hammer of 23%. It was determined that the lower rebound numbers resulted from energy losses associated with the extension of the impact plunger. This reduces the useful operating range of the modified hammer compared to the standard Schmidt hammer. Therefore, low compressive strength measurements will be limited by the effect of lower average rebound numbers. However, the lower rebound numbers can be normalized for direct comparison with standard Schmidt hammer data using the following relationship: Die x Anvil No. _ Doe x 60 ® n x R. ~ nx 46 Q) where: R Corrected rebound number r = Measured rebound numbers n = Number of measurements R, = Rebound number obtained on anvil This relationship was used to make comparisons between data obtained with the modified hammer and the standard Schmidt hammer during laboratory tests. Laboratory measurements were taken on six different concrete blocks (10x12x24 inches) using the modified Schmidt hammer and two standard Schmidt hammers. The top of each block had a rough wood trowel finish and the remaining sides were smooth, cast surfaces. Each block was a single mix of concrete, except block six, which contained three different concrete mixes and was divided into areas 1, 2, and 3. (The concrete floor in the laboratory was also used as a test block.) Dry measurements were taken with the three hammers on the top and sides of each block in the same general area. The average rebound numbers obtained from each block are presented in Table 3. The modified hammer data were normalized, using Equation 1, for direct comparison with the data obtained using the standard Schmidt hammers. Data from Table 4 obtained with the standard hammer (No. 1-8140) are compared against data obtained with the standard hammer (No. 2-8155) and the modified hammer (No. 8148) in Figure 12. The mean differences appear to be randomly distributed and are generally within the expected limits of +20% for the Schmidt hammer. Data obtained from the tops of the concrete blocks differed from the side measurements by as much as 44%. The rebound numbers were always much lower on the rough top surface than on the smooth cast-in-place sides. On blocks 3, 4, and 5, no readings were obtained from the top surface with the modified hammer because they were outside its operating range (too low). These data illustrate the effect of surface roughness on Schmidt hammer data. In actual field use, each measurement site must be thoroughly cleaned and smoothed in order to compare the results from one location with rebound numbers obtained at another point on the struc- ture. When the modified Schmidt hammer was initially tested submerged, the average rebound number obtained with the test anvil dropped to 45.2 and the standard deviation increased to 4.6. After practicing with the hammer underwater, the standard deviation of the readings dropped below 2.0 and the average rebound number increased to 46.1. This test demon- strated that the standard deviation of the readings could vary substan- tially even on the test anvil. Minor things such as keeping the hammer centered on the anvil, cleaning the anvil surface, maintaining a constant hammer position, etc., affect the measurement and the operator must use a consistent technique to increase the repeatability of the readings. It is necessary for each operator to practice with the hammer to develop a consistent technique. Measurements were taken underwater with the modified Schmidt hammer on the side of each test block in the same general area where the dry measurements were made. These data are tabulated in Table 4 along with the rebound numbers measured during the dry tests. Figure 13 is a plot of the dry versus wet data obtained with the modified Schmidt hammer. The rebound numbers obtained underwater tend to be higher than the comparable dry data, although they are still within the expected error band of +20%. The exception was the test results from block No. 4, which were considerably lower. It was determined that the rebound numbers from block No. 4, obtained underwater, were not taken in the same area as the dry measurements. This accounts for the shift in the data since block No. 4 was made with very low strength ready-mix concrete and the uniformity varied significantly. In summary, a Schmidt hammer was modified for underwater use and its use demonstrated in laboratory tests. The modification introduced an offset in the rebound data of 23% that limits the low compressive strength measurements compared to the standard hammer. After normaliza- tion, there were no significant differences between rebound numbers obtained with the modified hammer compared to the standard Schmidt hammer. The instrument can be used to rapidly survey concrete surface conditions to look for nonuniformity, provided the surface is adequately cleaned. A major redesign of the hammer will be required to remove the effect of lower rebound numbers that resulted from the initial modifi- cation. ULTRASONIC TESTING The transit time of high frequency sound waves through concrete can be used to assess its condition. Ultrasonic testing procedures for concrete have been standardized by ASTM Standard C-597 (Ref 10) and test equipment is available from commercial sources. Ultrasonic sound velocity tests were carried out on both laboratory test specimens and completed concrete structures. A detailed description of ultrasonic testing of concrete is presented in Reference 2 for terrestial applications. Background Ultrasonic testing of nonhomogeneous materials, such as concrete and timber, is significantly different than ultrasonic testing of homogeneous materials (metals). For example, when metals are tested ultrasonically, one objective is to detect internal flaws that send echoes back in the direction of the incident beam. These echoes are detected by a transducer that acts as both the transmitter and receiver. The position of the flaw can be determined from the measurement of the time taken for the pulse to travel from the surface to the flaw and back. This assumes a uniform sound velocity through the material being tested which is the case for metals. The thickness of metals is also measured in the same manner. 10 This approach cannot be applied to nonhomogeneous materials because echos are generated at the numerous boundaries of the different phases within these materials, resulting in a general scattering of the pulse energy in all directions. Also, the sound velocity through nonhomogeneous materials is not constant and depends on the material composition, density, and elastic properties. However, an average sound velocity can be measured and used to evaluate material composition and uniformity. Measuring the average sound velocity in materials such as concrete requires using separate transmit and receive transducers to avoid the energy scattering problem. The sound velocity is calculated by measuring the time required to transmit over a known path length. The measurement of average sound velocity through concrete is recommended as a means to establish the uniformity of the concrete being tested (Ref 2). It is not recommended that average sound velocity be correlated with concrete compressive strength, but rather that it be used only as an indicator of concrete quality. Table 5 presents some suggested sound velocity ratings for concrete and for comparison includes an average sound velocity for water (Ref 2). The two most important factors that affect the measurement of ultrasonic sound velocity through concrete are listed below and must be considered when making sound velocity measurements. Concrete Surface Finish. The smoothness of the surface under test is important for maintaining good acoustical contact between the face of the transducer and the surface of the concrete. Cast surfaces are gener- ally sufficient for routine testing and coupling agents such as silicone grease, water, etc. will help to improve coupling. Good acoustical coup- ling is necessary to obtain accurate sound velocity measurements. Presence of Reinforcing Steel. Sound velocity measurements taken near steel reinforcing bars may be high because the sound velocity in steel is 1.2 to 1.9 times the velocity in concrete. When the axis of the rebar is perpendicular to the direction of propagation, the influ- ence on sound velocity is generally small and if the quantity of rein- forcement is small the correction factors are on the order of 1 to 4% depending on the quality of the concrete. If the axes of the reinforcing bars are parallel to the direction of propagation, reliable corrections are difficult to make and it is recommended that sound paths be chosen that avoids the influence of reinforcing steel. The derivation of cor- rection factors to compensate for the effects of reinforcement on sound velocity measurements in concrete are covered in Reference 2 for both the perpendicular and parallel cases. Three approaches for measuring sound velocity in concrete are illus- trated in Figure 14. The most common method is direct transmission where the transducers are positioned on opposite sides of the test specimen and the longitudinal waves propagate directly toward the receiver. For indirect transmission, both transducers are placed on the same side of the concrete and energy scattered by discontinuities within the concrete is detected by the receive transducer. The strength of the pulse detec- ted in this case is generally less than 5% of the strength detected for the same path length when direct transmission is used. Semi-direct transmission is not normally used because it is difficult to maintain a consistent or known path length. 11 Direct transmission of the ultrasonic pulse is the preferred approach for measuring the average sound velocity in concrete because this method provides maximum sensitivity with a well defined path length. Indirect (surface) transmission is used when only one surface of the concrete is accessible, such as a concrete retaining wall. This approach does not have a well defined path length and indicates primarily the quality of the concrete near the surface. Equipment Description The ultrasonic equipment used for these tests was the Model C-4899 V-Meter manufactured by James Instruments, Inc., shown in Figure 15. This instrument is representative of commercially available ultrasonic devices used for laboratory and field testing of concrete. It generates low frequency ultrasonic pulses and measures the time for them to pass from one transducer to the other through the material between them. The V-Meter displays the transit time directly on a digital readout. The overall time measurement range is 0.1 to 9,990 microseconds, in three selectable intervals, with a resolution of 0.1, 1.0, and 10.0 micro- seconds, depending on the selected interval. The accuracy of the time measurement is +0.1 microseconds. The instrument can be operated from commercial power or a self-contained battery pack that provides 6 hours of continuous use. A detailed description of the Model C-4899 V-—Meter and its operation can be found in Reference 11. A pair of lead zirconate titanite (PZT-4) piezolectric transducers, operating at a frequency of 54 kHz, were used with the V-Meter. The piezoelectric elements were mounted in rugged stainless steel housings, modified for underwater operation. The coaxial cables connecting the transducers to the V-Meter were about 150 feet in length. A metal calibration bar was provided with the instrument to accurately set the zero time reference to compensate for the effects of cable length. Laboratory Evaluation The basic purpose of the laboratory tests was to evaluate the oper-— ation of the ultrasonic V-Meter for underwater use. Direct transmission data were collected to compare sound velocity measurements in dry concrete with measurements taken underwater. Indirect transmission was examined to evaluate the ability to detect cracks in concrete underwater. In addition, acoustical coupling effects were examined for both modes of transmission. Good acoustic coupling is necessary in order to make accurate and repeatable sound velocity measurements. For dry concrete, the surface must be reasonably smooth and a coupling agent, such as silicone grease is placed between the transducer and the concrete surface to make good acoustical contact and transfer maximum energy. If a coupling agent is not used, the transmitted signal is severely attenuated at the interface boundary between the transducer and the concrete surface due to the acoustic impedance mismatch. This results in large errors for the measurement of the transit time of the acoustic signal. Water is a reasonably good coupling agent and provides a significant improvement over air, but it was not good enough to match the dry measurements that 12 used silicone grease as the coupling agent. The difference between the wet and dry measurements depended on the smoothness of the concrete surface. The smoother the surface the closer they matched. Consequently, to reduce the error between the wet and dry measurements, silicone grease was also used underwater to improve acoustic coupling. The signal detection threshold of the V-Meter also causes erroneous transit time data to be recorded on the digital readout of the instrument. This happens when the amplitude of the first peak of the received signal is below the threshold voltage triggering level of the V-Meter. This effect is illustrated in Figure 16, taken from Reference 12, which also discusses this problem. When the instrument detects a following peak, this causes an apparent transit time increase of one-half wavelength or more. For example, if the sound velocity were 12,000 ft/sec in the con- crete under test and the frequency being used is 54 kHz, the wavelength of the transmitted signal is about 2.7 inches. An error of one-half wavelength under these conditions, over a path length of 1 foot, results in an 11% error in measured sound velocity. A plot of the haif-wavelength detection error as a function of path length and pulse velocity at 54 kHz is shown in Figure 17. This error is inversely proportional to the path length and the ultrasonic test frequency. Indirect transmission is more prone to errors associated with the detection threshold and the degree of acoustic coupling than direct trans- mission because of the much lower signal strengths. Two actual signal waveforms shown in Figure 18 for indirect transmission further illus- trate the problem. Both signals were transmitted through the same test block, over the same path length, but the coupling for the right waveform was much better than the left waveform as indicated by the received signal amplitude. The digital indication obtained from the V-Meter is shown on each waveform and indicates the detected peak. The difference in measured transit time was 29 microseconds, an error of approximately 20%. MThere- fore, during all acoustic measurements, silicone grease was used to improve acoustic coupling and the received signal was recorded on an oscilloscope to verify the digital readout from the V-Meter. Sound velocity measurements were taken on five concrete test blocks (10x11x24 inches), both dry and submerged in water. Direct transmission was used and the data are tabulated in Table 6 for comparison. Blocks 1, 2 and 3 would be rated as "good" concrete while blocks 4 and 5 would be rated 'questionable' according to Table 5. The average sound velocity measured when the blocks were dry was slightly higher than the average sound velocity when the blocks were submerged. The standard deviation of the dry measurements is slightly lower than for the measurements taken underwater. The trend of slightly higher averages, coupled with lower standard deviations for the dry measurements compared to the same measure- ments taken underwater was attributed to better acoustic coupling. However, as expected, there are no significant differences in measured sound velocity between the wet and dry measurements. Laboratory tests were conducted using indirect transmission to eval- uate the ability of ultrasonics to detect cracks in concrete that are around 1/32 of an inch wide and of varing depth. Several test specimens, each with a different depth crack, were made for the evaluation. The depths of the simulated cracks varied from 0.5 to 2.25 inches deep and the measured direct sound velocity through each specimen averaged about 3} 10,500 ft/sec, which indicates low strength concrete. Indirect measure- ments, however, did not indicate the simulated cracks in any of the test specimens during either the dry or wet tests. The calculated equivalent path length, based on the average sound velocity in the test specimen and the measured indirect time of flight, indicated the sound waves reflected off the back surface of the test block. The spacing between the transmit and receive transducers was maintained between 4 and 6 inches for these measurements. The test blocks should have been much larger in size to eliminate the effects of the reflected wave in order to draw conclusions from this series of tests. Indirect measurements were also taken on a prestressed octagonal concrete pile that had cracks around its circumference in five different locations along its length, as shown in Figure 19. All of the cracks were clearly visible and appeared to go completely through the pile. One crack near the end of the pile was much wider than the others. This crack was measured to be around 0.025 to 0.030 inch wide at the surface on the face were the measurements were made. The other cracks were estimated to range from 0.001 to 0.010 inch wide on the same surface. The actual width of a crack is very difficult to quantify because of its highly irregular three dimensional shape, and these are very approximate values. Indirect transit times were measured as a function of position along the prestressed pile and they are plotted in Figure 19 for a 6- and 8-inch path length. The positions of the transmit and receive transducers are indicated for each measurement, in addition to the location of the cracks. These data were taken with the pile dry and except for the large crack located at position number one, there was no apparent change in measured transit time for either path length due to the cracks. For the measurements taken across crack number one, the transit time for the 8-inch path length increased by 36% and for the 6-inch path length, the transit time increased by 68%. The increase in transit time for the sound pulse, due to the increased path length around the crack, can be used as a good indicator of the presence of large cracks in concrete but should not be used to estimate the depth of the crack. The transit time measurements did not change when the cracks were filled with water. In summary, ultrasonics can be used to categorize concrete by measuring the sound velocity in the material using direct transmission. Good acoustic coupling will enable accurate time measurements to be made for calculating sound velocity. Direct and indirect transmission can also be used to compare the general condition of the concrete from one location to another on the same structure, assuming the concrete mix is the same. Indirect transmission normally should not be used to obtain sound velocity measurements for categorizing or rating concrete because of the poorly defined sound path length. Indirect transmission appears to detect deep cracks (on the order of 0.030 inch wide) in concrete, but it did not detect other cracks that were much narrower but still clearly visible. 14 FIELD TEST RESULTS After the laboratory tests were completed, the R-Meter, Schmidt hammer, and V-Meter were used to collect data during a recent inspection (August 1984) of Pier J/K in San Diego, California (Ref 13). Ultrasonic testing was performed using the V-Meter and data were collected with the Schmidt hammer on selected piles to help assess the performance of these instruments in the field. The R-Meter was also used to collect data for assessing its performance. All of the instruments worked well during the field evaluations. Background Pier J/K is an old concrete, pile-supported, waterfront structure, located at the North Island Naval Air Station in San Diego. The pier is supported by 791 piles and was built in three phases: 1921, 1930, and 1958. The 1921 construction (about 45% of the pier) used a combination of 14- and 18-inch square conventionally reinforced piles. The 1930 construction (also about 45% of the pier) used 16-inch square conven- tionally reinforced piles. The remaining 10% of the pier was constructed in 1958 and it is supported on 16-inch octagonal prestressed piles. In 1981, this pier was inspected by Blaylock-Willis and Associates of San Diego, under contract to the Ocean Engineering and Construction Project Office (FPO-1), Naval Facilities Engineering Command (Ref 14). During this inspection, moderate to severe sulphate deterioration was observed in all the concrete piles constructed in 1921 and 1930. The inspection contractor speculated that Type I cement was used in those piles; this type of cement has not been considered appropriate for salt water use since around 1940. This inspection recommended that the pier live load be restricted to 100 pounds per square foot and truck cranes with capacities over 15 tons be prohibited. The contractor estimated the remaining useful life to be no greater than 5 years. In 1984, FPO-1 again contracted with Blaylock-Willis, at the request of the Naval Air Station, to reassess the condition of Pier J/K and update their recommendations. During this inspection, NCEL personnel worked with the contractor and FPO-1 to obtain NDT measurements on some of the deteriorated concrete piles. Data were also collected on a few of the 1958 piles (which were in excellent condition) for comparison. The overall results of this inspection confirmed the earlier findings. Before taking any NDT measurements, selected piles were thoroughly cleaned by the contractor using the NCEL's high pressure water jet cleaning system in conjunction with a rotary abrading tool attachment ("Whirl Away"). Both the water jet and rotary abrading tool removed some of the deteriorated surface area from the piles exhibiting extensive sulfate attack. Where this happened, it was not possible to obtain good NDT measurements using ultrasonics or the Schmidt hammer because of the surface roughness. (Relatively smooth surface areas are required to obtain good ultrasonic and Schmidt hammer data.) 15 Test Results R-Meter. The modified R-Meter was used to measure the depth of concrete cover over the rebar in five different piles from the 1930 construction group. The data obtained with the R-Meter are presented in Table 7 and a cross section view of the 1930 piles is shown in Figure 20. The rebar's configuration in the pile varied depending upon its location in the pile as shown in Figure 20. The amount of concrete cover was measured by positioning the probe of the instrument directly over the No. 6 rebar for measurements near the bottom of the pile and over the No. 7 rebar for the measurements taken near the top of the pile. A water depth reading was obtained at each measurement location. A very good peak reading was obtained on the R-Meter when the probe was directly over the No. 6 rebar on the lower portion of the pile. The measured depth of concrete cover over the No. 6 rebar averaged 1.89 inches thick. This number is in error by a small amount due to the effect of adjacent parallel rebar. The spacing between the rebars would have to be about 7.5 inches to eliminate this effect instead of the 5.5 inches indicated in Figure 20. The amount of error is difficult to quantify and the actual depth of concrete cover is thicker than the indicated depth. The actual depth was probably between 2 and 2.5 inches deep. When the probe was used near the top of the pile, a narrow peak reading could not be obtained and it was impossible to differentiate between the two adjacent No. 7 rebars. The effect of the parallel rebar was very apparent in these measurements and it strongly influenced the readings. The average depth of the concrete cover measured near the top of the piles was 4.64 inches. The actual depth of cover over the rebar was greater than the measured amount. The data indicate a large differ- ence between the construction plans as shown in Figure 20 and what was actually built. When taking measurements of concrete cover over the rebar in con- crete piles, the data usually will be influenced by the effect of closely spaced rebar. In some cases, it will not be possible to obtain narrow peak readings that indicate the actual location of the rebar due to the narrow spacing of the rebar with respect to the depth of concrete cover. The actual depth of concrete cover, however, will always be greater than the measured amount. Reducing the effects of closely spaced parallel rebar would require a major redesign of the instrument to alter the shape of the generated magnetic field. The field tests demonstrated that divers were able to use the instrument with very little training. The field tests also demonstrated that the instrument would be more effective if the diver collected the data after orienting the probe rather than depending upon a verbal com- munication link to the surface operator. A reel to handle the instru- mentation cables would also be benefical. Schmidt Hammer. The modified Schmidt hammer was used to measure the concrete surface hardness of selected piles from the 1930 and 1958 construction groups to evaluate its performance in the field. The data obtained with the modified Schmidt hammer are presented in Table 8 for the two different pile groups and include the anvil calibration data before and after the measurements. 16 Once a region on the pile was sufficiently cleaned, data could be taken with the Schmidt hammer as rapidly as the diver could operate the device. Operating the hammer was very simple for the diver; he only had to press the plunger of the hammer firmly against the pile until an impact was felt or heard. The diver then moved the hammer back away from the surface to automatically recock it, then the hammer was simply pressed against the surface again to take another measurement. This sequence was continually repeated and required less than 30 seconds to get 12 readings in any one area of the pile. The data were taken in regions near the top and bottom of each pile. These areas were previously cleaned and smoothed with a small carborundum stone by the diver. Twelve readings were taken at each location, then the high and low values were dropped before averaging. Twelve readings were not obtained in two locations for the 1930 piles numbered 93E and 93H because the surface was very soft and some of the readings did not register, since they were outside the range of the instrument. This soft surface condition is indicated by the limited data that were obtained. Also, only six readings were collected on pile 88H from the 1958 group because some fouling remained on the pile, creating a rough surface. The limited data from pile 88H did indicate a surface condi- tion comparable to the other 1958 piles. ; The average uncorrected rebound number of the data collected from the 1958 pile group was 37.9, which is 23% higher than the average uncor- rected rebound number of the 1930 pile group. This indicates a much softer surface condition on the piles from the 1930 group and would nor- mally indicate a lower strength concrete. This finding of a soft surface condition supports the conclusions from the previous inspection and indicates that the Schmidt hammer can be used to survey the surface con- dition of concrete underwater. In summary, the field test demonstrated that divers can easily use the Schmidt hammer underwater to obtain valid data on concrete surface hardness. The surface must be properly cleaned, however, to obtain consistent data. V-Meter. The V-Meter was used to collect ultrasonic data on selected piles from the 1930 and 1958 construction groups, using both direct and indirect transmission methods. For direct transmission, a pair of calipers were used by the diver to measure the transmission path length. The path length for indirect transmission was fixed at 10 inches between the centers of the transmit and receive transducer faces. Sili- cone grease was used on the face of each transducer to improve acoustic coupling. No fixtures were built to hold the transducers for direct measurements, the diver merely pressed them firmly against the concrete surface while the measurement was made. A small guide block was used to maintain the 10-inch spacing for the indirect measurements. The received acoustic signal was displayed on an oscilloscope and the pulse transit time was measured from the oscilloscope display to reduce detection threshold errors. If the received signal was a poor quality waveform, which was generally the case for the indirect measure- ments, several signals would be collected and averaged to obtain an improved signal-to-noise ratio. The received signal was also digitized and stored on magnetic tape for later analysis as required. 17 The ultrasonic data obtained using direct transmission through the piles are presented in Table 9. The table lists the pile, pulse transit time, path length, and calculated sound velocity through that particular section of the pile. Data were collected on piles in the 1930 and 1958 construction groups and a few measurements were also taken on the con- crete pile caps in bents 9 and 10. The data for the 1930 piles were divided into two groups. The piles from bents 8 and 9 were more severely damaged from sulfate attack than the piles from bent 93. The average sound velocity data for both groups of piles, however, was approximately the same and quite high (around 15,000 fps). All of these piles would be rated "good" to "excellent" using the suggested pulse velocity ratings for concrete presented in Table 5. The standard deviation of the measurements from the piles in bent 93 was lower than for the other group of piles from bents 8 and 9. The higher standard deviation was a direct result of a rougher surface condition on those piles. The direct transmission data for the 1958 piles given in Table 9 are not significantly different from the data collected on the 1930 piles. The mean sound velocity was higher (around 15,600 fps) by 4% and the standard deviation was smaller. All of the 1958 piles would be rated as “excellent” according to ratings from Table 5. From a visual inspection, these piles appeared to be in excellent shape and the Schmidt hammer data also indicated a much harder surface compared to the 1930 piles. A comparison of the direct transmission data for the two age groups of piles indicates no significant difference in the mean sound velocity measurements. This indicates that the effects of the sulfate attack occurring on the 1930 piles does not penetrate into the concrete enough to significantly alter the average sound velocity. In addition, these measurements indicate that the bulk compressive strength of the 1930 piles is quite high and comparable to the prestressed 1958 piles. Additional measurements should have been made near the top of the 1930 piles, above the waterline, to obtain reference measurements but at the time of the inspection this was not possible due to logistics problems. A reference measurement would have provided information to better estimate the depth of the sulfate attack in the concrete. A core sample from the piles at the point of measurement is required to accurately define the extent of the sulfate attack. Direct transmission data were collected in several locations on the pile caps over bents 9 and 10. Initially it was assumed these data could be used as a reference sound velocity, but it turned out that the pile caps were made from a different mix of concrete. The data indicated a much lower sound velocity compared to the measured sound velocity through the concrete in the piles. This is an indication of lower compressive strength; however, the concrete would still be rated as "sood". The standard deviation of these measurements was high, which indicates some variability in the concrete, because the concrete surface was smooth and good acoustic coupling was obtained for these measurements. In general, the direct transmission data do not indicate any significant difference between the concrete in the 1930 and 1958 pile groups. If the sulfate attack in the 1930 piles had only penetrated 1 inch into the concrete, for example, this would reduce the measured 18 sound velocity about 10% assuming the sound velocity through the damaged concrete dropped to 8,000 ft/sec. If reference measurements could have been made near the top of the piles, this change might have been detected. As it stands, the average sound velocity through the 1930 piles appears to indicate sound concrete when compared to similiar data from the 1958 piles that are not effected by the sulfate attack. Indirect ultrasonic measurements were made on the same piles as the direct measurements and at essentially the same locations. It was assumed that comparison of data from the two different pile groups would show some indication of the sulfate attack occurring on the 1930 piles. The data collected from the indirect measurements are tabulated in Table 10. The table lists the pile, general location of the measurement, measured pulse transit time over the fixed 10-inch path length, and general com- ments concerning the shape of the waveform displayed on the oscilloscope. Acoustic coupling was much more critical for these measurements compared to the direct measurements because of the reduced signal levels at the receive transducer. The average indirect transit time for the ultrasonic pulse in the 1930 piles was only about 1% higher than the average transit time for the 1958 piles. If only the data from "good" waveforms are considered, the difference is around 3.5%. From the direct sound velocity measurements, a difference of about 4% would be expected in the indirect measurements, which is the case if the data for the attenuated waveforms are dropped. Dropping these data has the most effect on the average for the 1958 piles. The 72-microsecond transit time for the top of pile 90H compared to 64 microseconds at the bottom corresponds to a half-wavelength difference in path length at 54 kHz. Therefore, these data do not show any signifi- cant differences in the ultrasonic pulse transit time through the 1930 piles compared to the 1958 piles. Thus, indirect ultrasonic measurements did not detect the sulfate attack occurring on the 1930 piles. Indirect measurements were also taken on the pile caps in the same location as the direct measurements. The indirect transit times were quite large compared to the indirect measurements taken on the piles. This can be illustrated by calculating an apparent sound velocity using 10 inches as the path length for the indirect measurements. For the 1930 piles this would be an average apparent sound velocity of 12,350 £t/sec, which can be compared to the direct measurement of 14,925 ft/sec, a decrease of about 17%. Calculating the same apparent sound velocity for the indirect measurements on the pile caps results in a value that is 45% lower than the direct measurement. This indicates that a rating system could be developed and applied to indirect measurements on concrete that has only one side accessible, even though a path length is not very well defined. In summary, neither the direct or indirect sound velocity measurements clearly indicated the sulfate attack on the piles in the 1930 group. The direct measurements indicated very sound concrete and did not indicate the sulfate attack (comparing data from the 1930 and 1958 pile groups). Likewise, there was no significant difference in the data from the two pile groups for the indirect measurements. Good reference readings obtained above the waterline on each pile would have provided more information. 19 Making ultrasonic measurements on concrete underwater was not dif- ficult and required very little diver training. The only real precautions to observe are: (1) make sure the measurement area is thoroughly cleaned, and (2) a good acoustic coupling is obtained. The actual measurement is very straight forward and easily performed by divers. In general, the data obtained in the field tests demonstrate the importance of combining Schmidt hammer and ultrasonic testing when inspecting concrete underwater. It is probable the sulfate attack has not penetrated very deep into the piles; consequently the effect on sound velocity through the pile would not be significant. The Schmidt hammer tests, however, did detect a much softer surface condition on the piles from the 1930 group compared to the 1958 piles, which was an indication of the sulfate attack. The extent of the sulfate attack into the piles could be confirmed by taking several core samples and performing a chemical analysis. CONCLUSIONS AND RECOMMENDATIONS 1. A commercially available magnetic rebar locator was successfully modified for underwater use. The R-Meter can be used to determine the location of rebar in concrete, measure the depth of concrete cover, and determine the size of the rebar. Laboratory and field tests of the instrument demonstrated that there was no effect on the output data after modification for underwater use. 2. A standard Schmidt hammer was successfully modified for under- water use and can be used to rapidly survey concrete surface hardness. The modification, however, introduced an offset in the rebound data of 23% compared to the same data obtained with an unmodified Schmidt hammer. Data can be normalized for direct comparison, but the offset does limit the low compressive strength measurements because the lower detection threshold was changed due to the hammer modifications. 3. Ultrasonics can be used successfully underwater to help evaluate the condition of concrete structures. A commercially available instru- ment was easily modified for underwater use. Laboratory and field tests of the instrument demonstrated there was no effect on the output data after modification. Both direct and indirect transmission methods can be used in the field to evaluate the uniformity of concrete and obtain a general condition rating. Cracks in concrete greater than 0.030 inches wide were detected in laboratory tests. 4, NCEL recommends that a prototype concrete inspection system be developed and evaluated for use by Navy UCT personnel and others to help inspect concrete structures underwater. This system should be comprised of an R-Meter, a Schmidt hammer, ultrasonic test equipment, and a common data acquisition system. The prototype Schmidt hammer should be designed to eliminate any data offset and retain the standard data range of the instrument, thus providing a direct correlation with standard Schmidt hammer test results. The prototype ultrasonic inspection system should be designed to minimize acoustic coupling effects and increase the measure- ment reliability. A diver operated mechanical device should be developed 20 to hold the transducers and measure the transmission path length automat- ically. A common data acquisition system should be developed to inter- face the three instrumentation systems mentioned above and discussed in this report. This system would collect and output data from each instru- ment for field evaluation and later analysis. 5. An integrated systems approach for the underwater inspection of concrete structures, as shown in Figure 21, is further recommended. This approach uses the underwater cleaning system developed by NCEL (Ref 15) as a key element, in addition to the three instruments dis- cussed in this report. The cleaning system is used to clean the con- crete for Level II and Level III inspections and provide a hydraulic power source to take core samples if required. The three instrumenta-— tion systems utilize a common data output and analysis system. Infor- mation from the inspection would indicate if concrete cores were required to complete the analysis of the structure. A rebar corrosion detection system, under development by NCEL (Ref 16), should be integrated into the underwater inspection system and, if possible, included as part of the R-Meter design. REFERENCES 1. Civil Engineering Laboratory. Technical Note N-1624: Inspection requirements analysis and nondestructive testing technique assessment for underwater inspection of waterfront tacilities, by R.L. Brackett, W.J. Nordell and R.D. Rail. Port Hueneme, Calif., March 1982. 2. V.M. Malhotra. Testing hardened concrete: Nondestructive methods, American Concrete Institute, Monograph No. 9. Detroit, Michigan, 1976. 3. R.L. Brackett. "Underwater inspection of waterfront facilities." The American Society of Mechnical Engineers, Publication No. 81-WA/OCE-5. New York, N.Y., 1981. 4. Naval Civil Engineering Laboratory Unpublished Report: Waterfront structures underwater inspection program plan, by R.L. Brackett. Port Hueneme, Calif., Feb 1984. 5. . Contract Report: NCEL underwater computerized tomography inspection study, Phase I. Santa Barbara, Calif., Ametek, Jun 1982. 6. . Contract Report: Preliminary design report for the underwater computerized axial tomography system for inspection of submerged structures. Santa Barbara, Calif., Ametek, Jun 1982. To . Contract Report: Economic assessment of computerized axial tomography inspection of timber and concrete waterfront structures, by R.R. King. San Antonio, Tex., Southwest Research Institute, Jan 1983. 21 8. James Instruments, Inc., Publication No. F-M—4956: Instruction manual for R-Meter, Model C-4956. Chicago, I11., Jun 1981. 9. Soiltest, Inc. Operating instructions for lightweight concrete Schmidt test hammer, Model RM-710. Evanston, I11., Dec 1978. 10. American Society for Testing and Materials. Designation C597-71: Standard test method for pulse velocity through concrete. Philadelphia, Penn., 1979. 11. James Instruments, Inc., Publication No. F-6062: Instruction manual for Model C-4899 V-Meter. Chicago, I11., May 1977. 12. Civil Engineering Laboratory. Technical Memorandum M—43-81-08: Ultrasonic inspection of wooden waterfront structures, by C.A. Keeney. Port Hueneme, Calif., May 1981. 13. Naval Facilities Engineering Command, Chesapeake Division, Ocean Engineering and Construction Project Office. Report No. FPO-1-84(19): Underwater facilities inspections and assessments at Naval Air Station, North Island, San Diego, California. Washington, D.C., Oct 1984. 14. - Report No. FPO-1-81(21): Underwater facilities inspections and assessments: Pier J/K, North Island Naval Air Station, San Diego, California. Washington, D.C., Oct 1981. 15. Naval Civil Engineering Laboratory. Technical Report R-909: A prototype high-pressure waterjet cleaning system, by C.A. Keeney. Port Hueneme, Calif., May 1984. 16. - Technical Memorandum M—52-85-01l: Electrochemical techniques for evaluation of corrosicn activity in marine reinforced concrete, by D.P. Polly. Port Hueneme, Calif., Nov 1984. 22 Table 1. Level of Inspection and Damage Detected for Underwater Concrete Structures Purpose Level I General visual to confirm as-built condition and detect severe damage Level II Detect surface defects normally obscured by marine growth Level III Detect hidden and incipient damage 23 Defects Severe mechanical or ice damage Surface cracking due to mechanical overload Severe corrosion of rebar Spalling of concrete surface Location of rebar Depth of concrete cover over rebar Incipient corrosion of rebar Internal voids Change in material strength Table 2. R-Meter Readings from Test Blocks in Inches of Concrete Cover Before Modification and After Modification with the Probe Submerged in Water R-Meter Readings Rebar (inches) Difference PLES Before | After Mod. — Mod. (submerged) No. 3 Test Block Position 24 Table 3. Schmidt Hammer Data Comparison - Dry Tests Mod. Hanmer] 1-2 | No. 8148 D.) Concrete Test Block l-side No. l-top No. 2-side No. 2-top No. 3-side No. 3-top No. 4-side No. 4-top No. 5-side No. 5-top No. 6-Area 1 No. 6-Area 2 No. 6-Area 3 No. /-Floor ib) (=) (e) SS i) CEO Omens Sie COLAC SOM COM GO sOe- O NYNOOWUONFrFOODWA LW ce Yer, le ek foil om sor ete asm aren icet te) PRADFEFNODOONAD LN er Number of Data Points: Average Difference: Standard Deviation: *Qutside operating range (too low). 25 Table 4. Modified Schmidt Hammer Data - Dry vs. Wet Concrete gine Dry Wet Wet—-Dry | W-D/W Avg/S.D. | Avg/S.D. vA . 38. No. 1 No. 2 No. 3 No. 4 No. 5 No. 6-Area 1 Sy) el eure titel: cess ANeProww wo WrRNrFOWWU oie sh teunele veyiais Ww OW CO ~ CO OO Ww No. 6-Area 3 | 37. Table 5. Ultrasonic Sound Velocity Ratings for Concrete Sound Velocity General Condition >15,000 >4,575 Excellent 12,000-15,000 3,660-4,575 Good 10,000-12,000 3,050-3,660 Questionable 7,000-10,000 2,135-3,050 Poor <7 ,000 <7) 5 ILS3S) Very Poor 4,860 1,480 Water 26 Table 6. Comparison of Direct Transmission Sound Velocity Data Average Sound Velocity (ft/sec) Concrete Dry Block 10,850 Table 7. R-Meter Measurements on Selected Piles from Pier J/K, Naval Air Station, North Island, San Diego, CA Pile Location/ Measured Concrete Depth (ft) Cover (inches) Top/1.3 Bot/16.8 Top/1.5 Bot/15.7 Top/0.8 Bot/16.1 Top/1.0 ~Bot/17.5 Top/1.0 Bot/15.0 SP hPrePhnN Hw He arg | (plist. olcm etc lecokne OoOnrrTIOONOFHLWD 5 7 - 6 o - 6 7 o © 5 of - 6 o I - 6 27 Table 8. Schmidt Hammer Data - Pier J/K Average Pi : ile Pile Number of Renaud Standard Ce es Group |} Number | Readings ete Deviation top bottom top bottom top bottom top bottom top bottom bottom top bottom top bottom top bottom 4.2 4.8 2.8 Uo3 5.8 11.7 3.3 6.8 7.3 8.8 0.6 — Calibration Anvil C 3 Before test After test 28 Table 9. Ultrasonic Data from Pier J/K —- Direct Transmission (a) Individual Pile Data Transmission Path Sound Bent Pile Time Length | Velocity (in.) (fps) Pile Group 15,450 14,650 14,035 14,815 15,390 15,750 Doawyot 15,050 15,565 15,215 14,560 bottom 14,560 bottom 14,560 top 15,445 top 14,560 bottom 15,050 top 15,050 bottom 14,560 bottom D D D E E E F F G G H 15,565 top 15,990 bottom 15,745 top 15,745 bottom 15,745 bottom 15,505 bottom 15,150 top mamma amaa 13,640 Data taken 14,150 on pile 13,515 caps near 13,290 piles 13,643 indicated 12,240 noma mt se continued 29 Table 9. Continued (b) Overall Sound Velocity (fps) Data Beats Nok Sound Velocity (ft/sec)-- Group oF ee [ee_[s:[ nnn [tc [tice] 7 1930, 15,015 | 633 14,035 15,750 Bents 8&9 1930, 14,925 | 384 14,560 15,565 Bent 10 1958 15,635 15,150 | 15,745 Pile Caps 13,413 | 640 | 12,240 | 14,150 (Dry) 30 Table 10. Ultrasonic Data from Pier J/K - Indirect Transmission (a) Individual Pile Data Transmission Pile Group Pile | Location Time Comments 1930-Path Good waveform Length 10 in. Good waveform (Bents 8&9) Good waveform 1930-Path top Good waveform Location 10 in. top Good waveform (Bent 93) top First 2 cycles attenuated bottom Good waveform bottom First 2 cycles attenuated top First 2 cycles attenuated bottom -—- top First 2 cycles attenuated bottom Good waveform bottom Good waveform top Good waveform top Good waveform bottom First 2 cycles attenuated top First 2 cycles attenuated top First 2 cycles attenuated bottom Good waveform bottom Good waveform top Good waveform bottom Good waveform Pile Cap Data taken on pile caps (dry) near piles indicated continued 31 Pile Group 1930-Path Length 10 in. (Bents 8&9) 1930-Path Length 10 in. (Bent 93) 1958 Pile Cap (dry) Table 10. Continued (b) Overall Indirect Transmission Time Indirect Transmission Time (usec) 32 \ AN WM AS RX .... c-4956 James Buwents Inc R-METER 2 BTY, OK Y 2 a duutintunluludaubnbonyy,, 2 . hath 1 Co NE LOTT, 4 s : RSS Ss (b) Closeup view of meter readout. Figure 1. R-Meter, Model C-4956. 33 concrete d rebar = | 0 fh Qa Ml depth of concrete cover ~) diameter of rebar Figure 2. Diagram illustrating measurement of concrete cover using R-Meter. 34 Linear Scale Meter Reading 100 90 80 70 Figure 3. suseeunue BEC EE EE EE EE EE EEE EEE EEEEEEEEEE EEE sane EEE EEE EERE EEE EERE EE EEE CREE EEE EERE et ay aeaseae searttast PEE BEER EE Soeeeseeees (Geers aasersasees seca sceesase F sect mia iG HH HA TT TTT | bao) Bao: Tt H HOGEDESaGnkoo Pty ! Gann eee anaes 1 Seceunueeeeenseecuae Tone oi! — Meer eosg Ff t aa (a ia = = Cae seeaz PE EEEE He HH A bi fesatesctiessts i i ieee Lie seesereeroaee PERE sradestitectiiocatitae EL aan IG ser Pee ane PERECSEE eras ait TEE He cae o ceases YT ScageenGG8 fag Ht tt sneee POPPE Eee 3 oO 50 ss sec iat Zero Offset Effects of zero setting errors. 35 Eu PRE ed isis 5 Fae Sheds ly Aiea) = RUAN BARE SE had eee Ne Oph A c™ iN 4 METER READING Figure 4. Diagram illustrating the effects of parallel one-inch-diameter rebar located two inches below the surface. 36 C- 4958 ROME TE (a) General view of modified R-Meter. ‘ ~~ ~~ (b) Closeup view of test probe. Figure 5. R-Meter modified for underwater use. 37 Linear Seale CWetd Figure 7. Figure 6. R-Meter on test block. 2 3 4 5 Linear Scale CDry) Plot comparing R-Meter readings before and after modification for underwater use. 38 (a) itis tiattiartantarttotiai ttt a ti General view of Schmidt Hammer. Hayy (b) Operating the Schmidt Hammer. 8. Schmidt Hammer, Model RM 710, Type L. 39 Note: (a) Figure 9. . Rider with guide rod . Two-part ring . Compression spring . Pawl . Hammer mass . Retaining spring . Impact spring _ Trip screw Impact plunger Test specimen Housing Scale Pushbutton Hammer guide bar Disk Cap Rear cover Guide sleeve Felt washer Plexiglass window Lock nut Pin Pawl spring Front fixation of Impact spring Rear end of impact. spring engaged to hammer mass PLLLLIOLL LLL 2d Plunger (I) in impacted position x Ss ee v OS BENE Cutaway view of Schmidt Hammer, Model RM 710, Type L. 40 BEnennes7n470 ae: VYAAPVY WY ELA SOI , VA AA 2 Resistance & la compressicn sur cylindre Mean error Dispersion moyenne Cylinder compression strength Test hammer rebound Durete au choc 24 Figure 10. General calibration chart that relates rebound number to cylinder compressive strength for the Model RM 710, Schmidt Hammer. Figure 11. Schmidt Hammer modified for underwater use. Al Wet Tests Modified Hammer — 8148 Figure 12. % 10 Figure 13. Hammer No. 2 — 8155 4 Modified hammer O Hammer No. 2 28 38 Hammer No. 1 — 8140 Plot of Schmidt Hammer data - dry. 28 32 48 Dry Tests Plot of modified Schmidt Hammer data. 42 58 qe 40 ao e ) , eo,” a.? a. Semi-direct Indirect Transmission Direct Transmission Transmission Methods of ultrasonic pulse transmission. Figure 14. 43 ‘ SW AC A (a) General view of ultrasonic test equipment. (b) Operating the V-Meter to collect data. Figure 15. V-Meter, Model C-4899. 44 Error C%) VOLTAGE THRESHOLD Ue EXPECTED TIME A LEVEL Is UNEXPECTED TIME a 17 ala Figure 16. Detection threshold effects on transit time measurement. 12 Path Length Cinches) Figure 17. Half-wavelength detection error. 45 dTIsnooe Aood jJo Adaezzoe oy. BuUTIeEAISNTTET swazoyzenem Teusts § v-30°T 6e°f 66°2 @8S°2 88° *JUsuleInseeu eT} JTSueAI, UO (WAOFeAeM AJeT) BuTtTdnoo 66°T 85°C 980°O dasi ozt = Wy 86 °S- G2 °f- By *c- OT °T- 62°68 yes °t 88 °c oye S ¥-38°s 66°e @S*2 @68°2 OS’"t "gI ean3ty Be*T 8S°e 86°0 sasn 6pt = Wy Ce a pS°?e- 89°T- 28° @- 68°@ 66°8 92°T 46 i O Transmit 8 in. Q Receive Transit Time (usec) Path Length Location (in.) Crack locations — octagonal concrete pile Figure 19. Measured indirect transit times as a function of position along a cracked prestressed concrete pile. 47 " Vp) au 3" = 3l/: "0 xr ro je a +8 16'SQ. 1930 PILE-UPPER 17' h | h #8 eS #6 /4\ 3 um a 16"SQ. 1930 PILE-BELOW 17’ Figure 20. Cross-section view of 1930 piles, Pier J/K. Pile Cleaning System @ Water Jet @ Mechanical e Hydraulic Power Source Concrete Coring Tools Visual Inspection Ultrasonic Testing e@ General Condition Assessment Schmidt Hammer “R’ Meter e REBAR Location @ Concrete Cover (1/4-8”) e REBAR Size (#3-#16) e Surface Hardness @ General Condition Assessment Data Display and Analysis Figure 21. Integrated Systems Approach to Underwater Concrete Inspection. @ Crack Detection 1/32” REBAR Corrosion Detection 48 Appendix NOMINAL DIMENSIONS OF REINFORCING STEEL A-1 Table A-1. Nominal Dimensions of Reinforcing Steel Number Diameter (inches) DISTRIBUTION LIST AF 18 CESS/DEEEM, Kadena, JA; ABG/DER, Patrick AFB, FL AFB AFIT/DET, Wright-Patterson AFB, OH; AFSC/DEEQ (P Montoya), Peterson AFB, CO; HO MAC/DEEE, Scott AFB, IL; HQ TAC/DEMM (Schmidt), Langley, VA; SAMSO/MNND, Norton AFB CA AFESC DEB, Tyndall AFB, FL; HQ AFESC/TST, Tyndall AFB, FL; HQ RDC, Tyndall AFB, Fl; HQ TST, Tyndall AFB, FL AFSC ESD/OCMS, Hanscom AFB, MA NATL ACADEMY OF ENG. Alexandria, VA ARMY AFZF-DE-EPS, Ft Hood, TX; AMCSM-WCS, Alexandria, VA; ARDC, Library, Dover, NJ; BMDSC-RE (H McClellan), Huntsville, AL; Ch of Engrs, DAEN-CWE-M, Washington, DC; Ch of Engrs, DAEN-MPU, Washington, DC; Comm Cmd, Tech Ref Div, Huachuca, AZ; ERADCOM Tech Supp Dir. (DELSD-L), Ft Monmouth, NJ; FESA-E (J. Havell), Fort Belvoir, VA; FESA-E (Krajewski), Fort Belvoir, VA; Facs Engr Dir, Contr Br, Ft Ord, CA; HODA (DAEN-ZCM); POJED-O, Okinawa, Japan ARMY - CERL CERL-ZN, Champaign, IL; Library, Champaign IL ARMY CORPS OF ENGINEERS HNDED-CS, Huntsville, AL; HNDED-FD, Huntsville, AL; Library, Seattle WA ARMY CRREL CRREL-EA, Hanover, NH ARMY CRREL CRREL-EG (Rsch CE), Hanover, NH ARMY CRREL Library, Hanover, NH ARMY DEPOT Letterkenny, Fac Engr (SDSLE-SF), Chambersburg, PA ARMY ENG WATERWAYS EXP STA Library, Vicksburg MS; WESCV-Z (Whalin), Vicksburg, MS; WESGP-E (Green), Vicksburg, MS; WESGP-EM (CJ Smith), Vicksburg, MS ARMY ENGR DIST Library, Portland OR; Phila, Lib, Philadelphia, PA ARMY ENVIRON. HYGIENE AGCY HSHB-EW, Aberdeen Proving Grnd, MD ARMY MAT & MECH RSCH CEN DRXMR-SM (Lenoe), Watertown, MA ARMY MTMC MTT-CE, Newport News, VA ARMY TRANSPORTATION SCHOOL ASTP-CDM, Fort Eustis, VA; ATSP-CDM (Civilla), Fort Eustis, VA ARMY-BELVOIR R&D CTR STRBE-AALO, Ft Belvoir, VA; STRBE-BLORE, Ft Belvoir, VA; STRBE-CFLO, Fort Belvoir, VA; STRBE-GS, Fort Belvoir, VA; STRBE-WC, Ft. Belvoir, VA ARMY-DEPOT SYS COMMAND DRSDS-AI, Chambersburg, PA ADMINSUPU PWO, Bahrain BUREAU OF RECLAMATION Code 1512 (C Selander), Denver, CO; J Graham, Denver, CO CBC Code 10, Davisville, RI; Code 155, Port Hueneme, CA; Code 156, Port Hueneme, CA; Code 430, Gulfport, MS; Dir, CESO, Port Hueneme, CA; Library, Davisville, RI; PWO (Code 80), Port Hueneme, CA; PWO, Davisville, RI; PWO, Gulfport, MS; Tech Library, Gulfport, MS CBU 401, OICC, Great Lakes, IL; 405, OIC, San Diego, CA; 411, OIC, Norfolk, VA; 417, OIC, Oak Harbor, WA CINCUSNAVEUR London, England CNO Code NOP-964, Washington DC; Code OP 22, Washington, DC; Code OP 23, Washington, DC; Code OP-987J, Washington, DC; Code OPNAV 09B24 (H); OP-098, Washington, DC COMCBLANT Code S3T, Norfolk, VA COMCBPAC Diego Garcia Proj Offr, Pearl Harbor, HI COMFAIRMED SCE, Naples, Italy COMFLEACT PWC (Engr Dir), Sasebo, Japan; PWO, Okinawa, Japan; PWO, Sasebo, Japan; SCE, Yokosuka Japan COMFLEACT, OKINAWA PWO, Kadena, Japan COMNAVACT PWO, London, England COMNAVAIRLANT Nuc Wpns Sec Offr, Norfolk, VA COMNAVLOGPAC Code 4318, Pearl Harbor, HI COMNAVMEDCOM Code 43, Washington, DC COMNAVRESFOR Code 08, New Orleans, LA COMNAVSUPPFORANTARCTICA DET, PWO, Christchurch, NZ COMNAVSURFLANT CO, Norfolk, VA; Code N42A Norfolk, VA COMNAVSURFPAC Code N-4, San Diego, CA COMOCEANSYSLANT Fac Mgmt Offr, PWD, Norfolk, VA COMOCEANSYSPAC SCE, Pearl Harbor, HI COMSPAWARSYSCOM Code PME 124-61, Washington, DC; PME 124-612, Washington, DC COMSUBDEVGRUONE CO, San Diego, CA; Ops Offr, San Diego, CA COMTRALANT SCE, Norfolk, VA NAVOCEANCOMCEN CO, Guam, Mariana Islands; Code EES, Guam, Mariana Islands NAVRESCEN PE-PLS, Tampa, FL DEFFUELSUPPCEN DFSC-OWE, Alexandria VA DIA DB-6E1, Washington, DC; DB-6E2, Washington, DC DIRSSP Tech Lib, Washington, DC DLSIE Army Logistics Mgt Center, Fort Lee, VA , DOE Wind/Ocean Tech Div, Tobacco, MD DTIC Alexandria, VA DTNSRDC Code 1706 (Alnutt), Bethesda, MD; Code 172, Bethesda, MD; Code 4111 (R. Gierich), Bethesda MD; Code 42, Bethesda MD; DET, Code 2724, Annapolis, MD; DET, Code 284, Annapolis, MD; DET, Code 4120, Annapolis, MD; DET, Code 522 (Library), Annapolis, MD ENVIRONMENTAL PROTECTION AGENCY ANR-458, Washington, DC EODGRU ONE DET, CO, Point Mugu, CA FAA Code APM-740 (Tomita), Washington, DC FCTC LANT, PWO, Virginia Bch, VA FMFLANT CEC Offr, Norfolk VA FOREST SERVICE Engrg Staff, Washington, DC GIDEP OIC, Corona, CA GSA Code FAIA, Washington, DC IRE-ITTD Input Proc Dir (R. Danford), Eagan, MN KWAJALEIN MISRAN BMDSC-RKL-C LIBRARY OF CONGRESS Sci & Tech Div, Washington, DC MARCORDIST 12, Code 4, San Francisco, CA MARCORPS FIRST FSSG, Engr Supp Offr, Camp Pendleton, CA MARCORPS AIR/GND COMBAT CTR ACOS Fac Engr, Okinawa MARINE CORPS BASE ACOS Fac engr, Okinawa; Code 4.01, Camp Pendleton, CA; Code 406, Camp Lejeune, NC; Dir, Maint Control, PWD, Okinawa, Japan; M & R Division, Camp Lejeune NC; Maint Ofc, Camp Pendleton, CA; PWO, Camp Lejeune, NC; PWO, Camp Pendleton CA MARINE CORPS HOTRS Code LFF-2, Washington DC MARITIME ADMIN B&D, Washington, DC MCAF Code C144, Quantico, VA MCAS Dir, Fac Engrg Div, Cherry Point, NC; Dir, Ops Div, Fac Maint Dept, Cherry Point, NC; PWO, Kaneohe Bay, HI; PWO, Yuma, AZ MCDEC M & L Div Quantico, VA; PWO, Quantico, VA MCRD SCE, San Diego CA NAF Dir, Engrg Div, PWD, Atsugi, Japan; PWO, Atsugi Japan NALF OIC, San Diego, CA NAS Code OL, Alameda, CA; Code 163, Keflavik, Iceland; Code 182, Bermuda; Code 18700, Brunswick, ME; Code 6234 (G. Trask), Point Mugu CA; Code 70, Marietta, GA; Code 72E, Willow Grove, PA; Code 83, Patuxent River, MD; Code 8E, Patuxent River, MD; Code 8EN, Patuxent River, MD; Dir, Engrg Div, Millington, TN; Dir, Maint Control Div, Key West, FL; Director, Engrg, Div; Engr Dept, PWD, Adak, AK; Engrg Dir, PWD, Corpus Christi, TX; Fac Plan Br Mgr (Code 183), NI, San Diego, CA; Lead CPO, PWD, Self Help Div, Beeville, TX; Oceana, PWO, Virginia Bch, VA; P&E (Code 1821H), Miramar, San Diego, CA; PWD Maint Div, New Orleans, LA; PWD, Maintenance Control Dir., Bermuda; PWO, Beeville, TX; PWO, Cecil Field, FL; PWO, Dallas TX; PWO, Glenview IL; PWO, Keflavik, Iceland; PWO, Key West, FL; PWO, Kingsville TX; PWO, Millington, TN; PWO, Miramar, San Diego, CA; PWO, Moffett Field, CA; PWO, New Orleans, LA; PWO, Sigonella, Sicily; PWO, South Weymouth, MA; PWO, Willow Grove, PA; SCE, Barbers Point, HI; SCE, Cubi Point, RP; Security Offr (Code 15), Alameda, CA; Security Offr, Kingsville, TX NATL BUREAU OF STANDARDS B-348 BR, Gaithersburg, MD NATL RESEARCH COUNCIL Naval Studies Board, Washington, DC NAVADMINCOM SCE, San Diego, CA NAVAIRDEVCEN Code 813, Warminster PA NAVAIRENGCEN Dir, Engrg (Code 182), Lakehurst, NJ; PWO, Lakehurst, NJ NAVAIREWORKFAC Code 100, Cherry Point, NC; Code 640, Pensacola FL; Code 64116, San Diego, CA; Equip Engr Div (Code 61000), Pensacola, FA; SCE, Norfolk, VA NAVAIRPROPTESTCEN CO, Trenton, NJ NAVAIRTESTCEN PWO, Patuxent River, MD NAVAUDSVCHQ Director, Falls Church VA NAVAVIONICCEN Deputy Dir, PWD (Code D/701), Indianapolis, IN; PW Div, Indianapolis, IN NAVCAMS PWO, Norfolk VA; SCE (Code N-7), Naples, Italy; SCE, Guam, Mariana Islands; SCE, Wahiawa HI; SCE, Wahiawa, HI; Security Offr, Wahiawa, HI NAVCHAPGRU Code 60, Williamsburg, VA NAVCOASTSYSCEN Code 2230 (J. Quirk) Panama City, FL; Code 423, Panama City, FL; Code 630, Panama City, FL; Code 715 (J. Mittleman) Panama City, FL; Code 719, Panama City, FL; Tech Library, Panama City, FL NAVCOMMSTA Code 401, Nea Makri, Greece; Dir, Maint Control, PWD, Diego Garcia; Dir, Maint Control, PWD, Thurso, UK; PWO, Exmouth, Australia NAVCONSTRACEN Code B-1, Port Hueneme, CA NAVEDTRAPRODEVCEN Tech Lib, Pensacola, FL NAVELEXCEN DET, OIC, WINTER HARBOR, ME NAVENVIRHLTHCEN Code 642, Norfolk, VA NAVEODTECHCEN Tech Library, Indian Head, MD NAVFAC Maint & Stores Offr, Bermuda; PWO, Centerville Bch, Ferndale CA NAVFACENGCOM Code 03, Alexandria, VA; Code 03T (Essoglou), Alexandria, VA; Code 04A1, Alexandria, VA; Code 04B (M. Yachnis), Alexandria, VA; Code 04B3, Alexandria, VA; Code 04M, Alexandria, VA; Code 04M1A, Alexandria, VA; Code 04T1B (Bloom), Alexandria, VA; Code 0474, Alexandria, VA; Code 0415, Alexandria, VA; Code 051A, Alexandria, VA; Code 07A (Herrmann), Alexandria, VA; Code 07M (Gross), Alexandria, VA; Code 09M124 (Tech Lib), Alexandria, VA: Code 100, Alexandria, VA; Code 1002B, Alexandria, VA; Code 1113, Alexandria, VA; Code 113C, Alexandria, VA NAVFACENGCOM - CHES DIV. Code 101, Washington, DC; Code 403, Washington, DC; Code 405, Washington, DC; Code 406C, Washington, DC; Code 407 (D Scheesele) Washington, DC; Code FPO-1C Washington DC; Code FPO-1E, Washington, DC; Code FPO-1E, Washington, DC; FPO-1, Washington, DC; FPO-1P/1P3, Washington, DC NAVFACENGCOM - LANT DIV. Br Ofc, Dir, Naples, Italy; Code 1112, Norfolk, VA; Code 403, Norfolk, VA; Library, Norfolk, VA NAVFACENGCOM - NORTH DIV. CO, Philadelpnia, PA; Code 04, Philadelphia, PA; Code 04AL, Philadelphia PA; Code 09P, Philadelphia, PA; Code 11, Philadelphia, PA; Code 111, Philadelphia, PA; Code 405, Philadelphia, PA NAVFACENGCOM - PAC DIV. (Kyi) Code 101, Pearl Harbor, HI; Code 09P, Pearl Harbor, HI; Code 2011, Pearl Harbor, HI; Code 402, RDT&E, Pearl Harbor, HI; Library, Pearl Harbor, HI NAVFACENGCOM - SOUTH DIV. Code 1112, Charleston, SC; Code 405, Charleston, SC; Code 406, Charleston, SC; Geotech Section (Code 4022), Charleston, SC; Library, Charleston, SC NAVFACENGCOM - WEST DIV. 09P/20, San Bruno, CA; Code 04B, San Bruno, CA; Code 102, San Bruno, CA; Dir, PWD (Code 018), San Bruno, CA; Library (Code 04A2.2), San Bruno, CA; RDT&E LnO, San Bruno, CA NAVFACENGCOM CONTRACTS AROICC, Quantico, VA; Code 460, Portsmouth, VA; DOICC, Diego Garcia; DROICC, Lemoore, CA; DROICC, Santa Ana, CA; OICC, Guam; OICC, Rota Spain; OICC-OICC, Virginia Beach, VA; OICC/ROICC, Norfolk, VA; ROICC (Code 495), Portsmouth, VA; ROICC, Code 61, Silverdale, WA; ROICC, Corpus Christi, TX; ROICC, Crane, IN; ROICC, Jacksonville, FL; ROICC, Keflavik, Iceland; ROICC, Key West, FL; ROICC, Point Mugu, CA; ROICC, Rota, Spain; ROICC, Twentynine Plams, CA; ROICC/AROICC, Brooklyn, NY; ROICC/AROICC, Colts Neck, NJ: ROICC/OICC, SPA, Norfolk, VA; SW Pac, Dir, Engr Div, Mania, RP; SW Pac, OICC, Manila, RP NAVFUEL DET OIC, Yokohama, Japan NAVHOSP CE, Newport, RI; CO, Millington, TN; Dir, Engrg Div, Camp Lejeune, NC; PWO, Guam, Mariana Islands; PWO, Okinawa, Japan; SCE (Knapowski), Great Lakes, IL; SCE, Camp Pendleton CA; SCE, Pensacola FL; SCE, Yokosuka, Japan NAVMAG Engr Dir, PWD, Guam, Mariana Islands; SCE, Guam, Mariana Islands; SCE, Subic Bay, RP NAVMEDCOM MIDLANT REG, PWO, Norfolk, VA; NWREG, Head, Fac Mgmt Dept, Oakland, CA; SEREG, Head, Fac Mgmt Dept, Jacksonville, FL; SWREG, Head, Fac Mgmt Dept, San Diego, CA; SWREG, OICC, San Diego, CA NAVMEDRSHINSTITUTE Code 47, Bethesda, MD NAVOCEANO Code 3432 (J. DePalma), Bay St. Louis MS; Code 6200 (M Paige), Bay St. Louis, MS; Library Bay St. Louis, MS NAVOCEANSYSCEN Code 5204 (J. Stachiw), San Diego, CA; Code 6700, San Diego, CA; Code 90 (Talkington), San Diego, CA; Code 944 (H.C. Wheeler), San Diego, CA; Code 964 (Tech Library), San Diego, CA; Code 9642B (Bayside Library), San Diego, CA; DET, R Yumori, Kailua, HI; DET, Tech Lib, Kailua, HI NAVORDMISTESTSTA Dir, Engrg, PWD, White Sands, NM NAVORDSTA PWO, Louisville, KY NAVPETOFF Code 30, Alexandria, VA NAVPGSCOL C. Morers, Monterey, CA; Code 68 (C.S. Wu), Monterey, CA; E. 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NOAA Joseph Vadus, Rockville, MD; Library, Rockville, MD; M Ringenbach, Rockville, MD NORDA Code 410, Bay St. Louis, MS; Ocean Prog Off (Code 500), Bay St. Louis, MS; Ocean Rsch Off (Code 440), Bay St. Louis, MS NRL Code 5800 Washington, DC; Code 6120 (R. Brady Jr), Washington, DC USCG Code 2511 (Civil Engrg), Washington, DC NSC Cheatham Annex, PWO, Williamsburg, VA; Code 54.1, Norfolk, VA; Code 700, Norfolk, VA; Fac & Equip Div (Code 43) Oakland, CA; SCE, Charleston, SC; SCE, Norfolk, VA NSD SCE, Subic Bay, RP CBU 401, OICC, Great Lakes, IL NUSC DET Code 3322 (Brown), New London, CT; Code 3322 (Varley) New London, CT; Code EA123 (R.S. Munn), New London, CT; Code TA131 (G. De la Cruz), New London CT OCNR Code 126, Arlington, VA OFFICE SECRETARY OF DEFENSE OASD (MRA&L) Dir of Energy, Washington, DC CNR DET, Code481, Bay St. Louis, MS; DET, Dir, Boston, MA OCNR Code 421 (Code E.A. Silva), Arlington, VA; Code 700F, Arlington, VA PACMISRANFAC PWO, Kauai, HI PERRY OCEAN ENG R. 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DEPARTMENT OF THE NAVY POSTAGE AND FEES PAID NAVAL CIVIL ENGINEERING LABORATORY DEPARTMENT OF THE NAVY PORT HUENEME, CALIFORNIA 93043 pop-si6 US PMAIL Sas © OFFICIAL BUSINESS PENALTY FOR PRIVATE USE, $300 1 IND-NCEL-2700/4 (REV. 12-73) 0930-LL-L70-0044 Commanding Officer Code L14 Naval Civil Engineering Laboratory Port Hueneme, California 93043 DISTRIBUTION QUESTIONNAIRE The Naval Civil Engineering Laboratory is revising its primary distribution lists. SUBJECT CATEGORIES SHORE FACILITIES Construction methods and materials (including corrosion control, coatings) Waterfront structures (maintenance/deterioration control) Utilities (including power conditioning) Explosives safety Construction equipment and machinery Fire prevention and control Antenna technology Structural analysis and design (including numerical and computer techniques) 10 Protective construction (including hardened shelters, shock and vibration studies) 11 Soil/rock mechanics 13 BEQ 14 Airfields and pavements 15 ADVANCED BASE AND AMPHIBIOUS FACILITIES 16 Base facilities (including shelters, power generation, water supplies) 17 Expedient roads/airfields/bridges 18 Amphibious operations (including breakwaters, wave forces) 19 Over-the-Beach operations (including containerization, materiel transfer, lighterage and cranes) 20 POL storage, transfer and distribution 24 POLAR ENGINEERING 24 Same as Advanced Base and Amphibious Facilities, except limited to cold-region environments NR ONDINDH Sw TYPES OF DOCUMENTS 85 Techdata Sheets 86 Technical Reports and Technical Notes 83 Table of Contents & Index to TDS 28 ENERGY/POWER GENERATION 29 Thermal conservation (thermal engineering of buildings, HVAC systems, energy loss measurement, power generation) 30 Controls and electrical conservation (electrical systems, energy monitoring and control systems) 31 Fuel flexibility (liquid fuels, coal utilization, energy from solid waste) 32 Alternate energy source (geothermal power, photovoltaic power systems, solar systems, wind systems, energy storage systems) 33 Site data and systems integration (energy resource data, energy consumption data, integrating energy systems) 34 ENVIRONMENTAL PROTECTION 35 Solid waste management 36 Hazardous/toxic materials management 37 Wastewater management and sanitary engineering 38 Oil pollution removal and recovery 39 Air pollution 40 Noise abatement 44 OCEAN ENGINEERING 45 Seafloor soils and foundations 46 Seafloor construction systems and operations (including diver and manipulator tools) 47 Undersea structures and materials 48 Anchors and moorings 49 Undersea power systems, electromechanical cables, and connectors 50 Pressure vessel facilities 51 Physical environment (including site surveying) 52 Ocean-based concrete structures 53 Hyperbaric chambers 54 Undersea cable dynamics 82 NCEL Guide & Updates 91 Physical Security @ None— remove my name DEPARTMENT OF THE NAVY NAVAL CIVIL ENGINEERING LABORATORY POSTAGE AND FEES PAID PORT HUENEME, CALIFORNIA 93043 DEPARTMENT OF THE NAVY OFFICIAL BUSINESS DOD-316 PENALTY FOR PRIVATE USE, $300 375i-—., 82392001.) “64 t Document Library LO=205 f See ate woods Hole Oceanogracnic institution Woods Hole, MA 02543=0000 46,47248.49.52.79.82.86 |