Experimental investigation and refined predictive model for cement-treated expansive soils

Expansive soils exhibit poor engineering performance and substantial swelling potential. Therefore, stabilisation is crucial to mitigate geological hazards triggered by exposure to moisture or load changes. In this study, the effects of mixture ratio, curing time and curing temperature on the properties of cement-treated expansive soil were investigated. Specifically, soil specimens containing 0, 5, 10 and 15% cement were cured for 1, 7, 14 and 28 days at 20, 40 and 60°C, then evaluated for compaction and unconfined compressive strength. Furthermore, chemical and microstructural changes were analysed by way of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The findings indicate that increasing cement content non-linearly enhances soil properties. In addition, SEM and XRD analyses confirm that hydration and pozzolanic products effectively fill voids and strengthen particle bonds. The reaction is rapid for the first 7 days, then stabilises, with higher temperatures increasing the rate. Moreover, a refined model was developed to unify key curing parameters and address oversimplified linear cement-strength relationships prevalent in the existing literature. The model's results show strong agreement with the empirical findings (R2=0.97). Collectively, these findings offer a comprehensive insight into the cement stabilisation of expansive soil across diverse curing conditions and establish a robust framework for predicting strength development.