Influence of Compaction Characteristics and Moisture Exposure on Resilient Moduli of Cement-Treated Soil

The resilient modulus (MR) of subgrade soil is a key parameter for mechanistic-empirical pavement design of flexible pavements. Generally, MR is determined by conducting repeated load triaxial (RLT) tests in the laboratory and is used to characterize the subgrade soil behavior under repeated traffic loading conditions. This research study investigated the influence of compaction energy and moisture exposure on the resilient moduli of untreated and cement-treated cohesive soil. For RLT tests, untreated and cement-treated cylindrical specimens were prepared at respective optimum moisture contents and maximum dry unit weights, obtained from both standard and modified Proctor compaction tests. Compacted cement-stabilized soil specimens were cured in a humid room for seven days before they were subjected to RLT tests. Three-parameter universal model constants (k(1), k(2), and k(3)) were determined by performing statistical regression analysis on RLT test results. Test results indicate that the compaction energy has a major impact on both the resilient moduli and stress hardening/softening behavior of untreated and cement-treated soils. The untreated soil specimens of standard Proctor compaction energy exhibited stress softening behavior with an increase in deviator stress, whereas the untreated specimens with modified Proctor compaction energy exhibited stress hardening behavior. In contrast, the cement-treated specimens showed stress hardening behavior with an increase in deviator stress, irrespective of the compaction energy. This might be because specimens tend to get hardened when subjected to higher axial loading, which resulted in low axial strains and exhibited high resilient modulus. Results show a slight decrease in resilient moduli of cement-treated soil after 4 h of submerging in water.