PCS replacement percentage

^ LATE STRENGTH (7D) CONTROL (701

Figure 4 Effect of PCS replacement percentage on strength: soil 1.

This is observed for early and late stages. When comparing the contaminant type effect on the strength of concrete containing fine-particle soil, no conclusive observations were obtained for soil 2 (clay-silt with 0.12% oil contamination) vs. soil 5 (clay-silt with 0.15% gasoline contamination). The effect of soil type on the strength of concrete containing PCS was found to be very important. The presence of soil with fine contaminated particles (soil 2) yields a lower strength than concrete mixed with sandy contaminated soil (soil 1). Whereas for soil 1 an average of 13% strength reduction is observed at a PCS/sand replacement ratio of 40%, the inclusion of soil 2 results in a strength reduction of about 45%.

The results of the wet-dry and freeze-thaw tests are presented in Table 13. The tests were conducted on the control mixture and the C3 mixture of all five soils. These results present the percentage of weight loss for a 2 x 2 x 10 in. prism subjected to the wet-dry and freeze-thaw cycles. In general, the percentage of loss for all tested specimens was less than 2%. No visible cracking or surface deterioration could be observed on any of the tested specimens at the end of the test procedure. These preliminary results indicate that up to 40% PCS/sand replacement ratio could be used without seriously affecting the integrity of concrete members. However, more tests are required before such a conclusion can be confirmed.

Leaching tests were conducted in duplicate for soils 1-5 using mixture C3 (20 samples) after 24 hr for a test duration of 96 hr and after 10 days for a test duration of 24 hr. All of these samples were nondetectable for benzene. The detection limit was 0.01 ppm. It is apparent that

COMPRESSION

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PCS replacement percentage

EARLY STRENGTH (2D) ^ LATE STRENGTH (70!

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PCS replacement percentage

EARLY STRENGTH (2D) ^ LATE STRENGTH (70!

COMPRESSION

70001-

1000

PCS replacement percentage

■ EARLY STRENGTH (!DI LATE STRENGTH (TDI - CONTROL (70)

COMPRESSION

70001-

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1000

PCS replacement percentage

■ EARLY STRENGTH (!DI LATE STRENGTH (TDI - CONTROL (70)

1200 1000 800

FLEXURAL

PCS replacement percentage

Figure 5 Effect of PCS replacement percentage on strength: soil 2.

PCS replacement percentage

1200 1000 800

FLEXURAL

Figure 5 Effect of PCS replacement percentage on strength: soil 2.

the amount of benzene leaching from concrete was not sufficient to produce a measurable response. To increase the sensitivity of the leaching test, it was decided to create a soil artificially contaminated with neat benzene. Samples from soils 1 and 3 were left in an oven at 105°C for 4 hr to drive off VOCs. The samples were left uncovered overnight to allow rehydration. Contaminant concentration of 0.5% and 3% benzene (Cs in Table 14) were added by weight basis. Samples free of contamination were used as a control. Concrete cubes were made using C3 mixture proportions. The leachability results, after 24 hr, for concrete containing artificially contaminated soils and for loose soils are shown in Table 14. The loose soil results (designated mix L) indicated that soil 3 leached about twice the benzene at 0.5% benzene contamination as indicated by the benzene concentration in the water (Cw) at the end of the test. At 3.0% benzene concentration, little difference was observed between the behavior of the two soils. Since the soils were not in a solid matrix, mass transport in this system is relatively nonlimiting. It is likely that the concentrations observed are more indicative of the adsorption behavior of the soils Thus it can be concluded that soil 1 is a stronger absorber than soil 3. A possible reason why there was little difference at the higher concentration is that the concentration may be approaching the solubility limit in this system. The leachate concentration, Cw, for the PCS concrete cubes ranged from 0.55 to 40 ppm. The leaching increased with the increase of contaminant concentration for both soil types. The cube surface leaching flux (A/) varied from 0.003 to 0.217 g/(hr-m2). The fraction of benzene in the cubes that leached (fL) was 0.111.27%. These levels are about 99% lower than the values for loose soil in the case of 0.5% contamination, and about 95% lower for the case of 3% contamination.

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PCS replacement percentage

7000 6000 5000 4000 3000 2000 1000 0000

COMPRESSION

PCS replacement percentage

FLEXURAL

S 12001-

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