Abstract

The objectives of this research were to evaluate the sensitivity of indirect tensile strength (ITS) test results to stabilizer type, stabilizer concentration, and curing time for multiple clayey soils with varying plasticity indices (PIs), identify cases in which an ITS of 30 psi can be obtained, and create a general linear model that predicts ITS. The scope of work included laboratory testing of three clayey soils sampled from Monticello, Utah; Bloomington, Indiana; and San Antonio, Texas. Each soil was tested using two stabilizers, cement or lime, at three concentrations, and two replicate samples were prepared for each combination. ITS testing was performed on two specimens of each combination at curing times of both 7 days and 28 days, for a total of 72 tests. The procedures outlined in this study include soil characterization, determination of moisture-density relationships, Eades and Grim testing, soil preparation, soil compaction, ITS testing, and statistical analysis. Regarding stabilizer type, treatment with cement consistently yielded higher ITS values than treatment with lime. Regarding stabilization concentration, ITS consistently increased with increasing concentrations of cement for all three soils; however, the effect of lime concentration depended on the PI of the soil, where increasing ITS values were only apparent with higher PI values. Regarding curing time, the ITS values corresponding to 28 days were generally higher than those corresponding to 7 days. Differences in ITS among the soils were largely attributable to differences in PI, which can influence pozzolanic reactivity. A cement or lime concentration that was equal to or 2% above the lime concentration indicated by the Eades and Grim test was typically required for a minimum 28-day ITS value of 30 psi to be attained. For the model developed to predict ITS, the significant predictor variables included PI, stabilizer type, actual stabilizer concentration, and curing time, as well as the two-way interactions between PI and stabilizer type, PI and actual stabilizer concentration, PI and curing time, and stabilizer type and actual stabilizer concentration. Overall, the model has an R2 value of 0.943 and an adjusted R2 value of 0.936. The model is best suited for soils having a fines content greater than 50%, a PI greater than 20, and a soluble sulfate concentration less than 3000 ppm.

Degree

College and Department

Ira A. Fulton College of Engineering

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