Master of Science in Civil Engineering (MSCE)


Civil and Environmental Engineering

Document Type



To evaluate the effect of high moisture content on the performance of weak subgrade soil and improve the engineering properties of weak subgrade soil through using cementitious materials, five different soils that represent range of subgrade soil in Louisiana (based on plasticity indices) were collected and considered in this research study. All tests on raw soils and treated/stabilized soils were performed on the soil laboratory at the Louisiana Transportation Research Center (LTRC). Ordinary Portland cement and hydrated lime were selected in this study to treat/stabilize the subgrade soils depending upon the soil type and plasticity index. The repeated load triaxial (RLT) tests were performed on the laboratory molded treated/stabilized specimens in order to evaluate their resilient modulus and to study their deformation behavior under cyclic loading. In order to simulate the field conditions for the pavement construction over weak subgrade layer to create working platform and/or subbase layer, the soil/stabilizers were mixed at three different moisture contents in the wet side of optimum moisture content. A total of 84 resilient modulus tests and similar number of single-stage permanent deformation tests were performed under cyclic loading conditions. Moreover, 54 multi-stage permanent deformation tests were also performed to characterize the behavior of the material based on shakedown limits. A good relation was observed between the water/stabilizer ratio and the repeated loading characteristic of the specimens tested from resilient modulus, single-stage permanent deformation, and multi-stage permanent deformation tests. The soil specimens compacted at low water/stabilizer ratio showed better performance than those compacted at high water/stabilizer ratio having identical unconfined compressive strength (UCS). Regression analyses were also performed on the available models to predict resilient modulus based on the results of laboratory tests and the regression coefficients (k1, k2, k3) were evaluated for all soil/stabilizer conditions.



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Committee Chair

Murad Yusuf Abu-Farsakh