Influence of Gypsum Content and Curing Time on the Strength Behavior of Kaolin Soil

The reusage of gypsum-based construction materials in geotechnical applications provides a sustainable alternative for soil stabilization. In this study, the effects of synthetic gypsum (CaSO4·½H2O) on the physical and mechanical properties of a low-plasticity silt (ML) type kaolin soil were experimentally investigated. Atterberg limit, standard Proctor and unconfined compressive strength (UCS) tests were applied on untreated and treated soil samples by rates of 2%, 5%, 8%, and 11% gypsum by dry weight for curing periods of 1 and 15 days. The results of the experiments revealed a significant change in the mechanicai behavior of the soil by the usage of gypsum treatment. The soil plasticity decreased by low to moderate gypsum additive while an improvement was observed for the compaction characteristics pointing out a denser and more stable particle structure. A clear improvement has been observed for strength properties of the soil with increasing gyspum content up to an optimum level, pointing out an enhancement for interparticle bonding and pozzolanic interactions in the soil matrix. Besides, higher gypsum rates resulted in a strength reduction by increased deformability, pointing out a distortion in the soil fabric and the formation of less effective bonding at excess rate of binder contents. Consequently, the findings revealed that construction material type gypsum can serve as an effective stabilizing binder for ML-type soils when applied at moderate rates. However potential durability problems and long-term performance should be carefully considered in practical applications.