Evaluating the Performance of Cementitious Treated/Stabilized Very Weak and Wet Subgrade Soils for Sustainable Pavement

To evaluate the effect of high moisture content on the performance of subgrade soil and examine the appropriate ways to improve the engineering properties of very wet and weak subgrade soil through using cementitious materials (cement, lime, and/or fly ash), five different soils that represent range of subgrade soil in Louisiana (based on plasticity indices) were collected and considered in this research study. In order to simulate the field conditions for the pavement construction over very weak subgrade layer to create working platform (a target 7-day UCS of 345 kPa) and/or subbase layer (a target 7-day UCS of 690 kPa), the soil/stabilizers were mixed at three different moisture contents in the wet side of optimum moisture content. 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. A good relation was observed between the water/stabilizer ratio and the resilient modulus/permanent deformation. 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). The test results also showed that the permanent deformation is somehow negligible (permanent strain < 0.09%) that might be ignored in the pavement design.