Insights into the Influence of Environmental Stressors on Expansive Subgrades Stabilized with Different Calcium-Based Stabilizers for Resilient Transportation Infrastructure

Although chemical stabilization is well practiced in dealing with expansive soils, these soils’ endurance to extreme weather events is still questionable because of potential alterations in microstructure and degradation of stabilization products. This study, therefore, investigates how moisture and temperature variations affect the structure and engineering behavior of chemically stabilized expansive clay. A series of unconfined compressive strength tests were conducted before and after freezing–thawing (FT) and wetting–drying (WD) conditioning on high-plasticity clay stabilized with cement or hydrated lime, with lime sludge as a co-additive. Cement treatment resulted in a higher initial strength (3.1 MPa) compared with hydrated lime treatment (1.3 MPa), primarily as a result of the rapid formation of binding gels through cement hydration. However, environmental conditioning and post-conditioning testing protocols significantly affected the void ratio and saturation levels of specimens, yielding different strength values for both cement and lime treatments. Cement-treated specimens experienced a strength reduction under both FT and WD conditions, with a more pronounced decrease after WD. However, lime-treated specimens exhibited an interesting trend of getting weakened after FT but becoming stronger after WD. These differences are mainly attributed to variations in the evolution of void ratio and saturation levels during the respective conditioning and post-conditioning phases. To further confirm these links, data from the experiments was fed into a random forest regression model to identify key factors influencing the engineering performance. Sensitivity analysis showed the degree of saturation (0.53) to be marginally more influential than the void ratio (0.47) in determining the strength, aligning with the experimental findings.