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 

 "good". 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 



