Engineering properties of expansive soil stabilized by physically amended titanium gypsum

The deposition of large amounts of industrial solid waste titanium gypsum via weathering causes wastage of land resources and environmental pollution. The resource utilization of titanium gypsum is mainly limited by its low reaction rate. This paper presents a simple physical modification to improve the performance of titanium gypsum for use in the stabilization of expansive soils. The engineering properties and mechanisms of stabilized soils were investigated by combining the evaluation of stabilized soil properties including physical properties, deformation characteristics, mechanical capacity, microstructure, and mineral evolution on a macroscopic and microscopic scale. The results showed that the coarse particles of the soil increased and the plasticity index, swelling potential shrinkage, and compression index decreased while the strength characteristics of unconfined compressive strength, cohesion and internal friction angle of the stabilized soil were significantly improved. Furthermore, a curing time of 7 d was recommended for stabilizing the expansive soil. Microcosmic experiment results revealed the densification process of the internal structure and reflected the ion exchange, coagulation, and agglomeration of the stabilized soil. Moreover, stabilized soil at 25% titanium gypsum admixture can satisfy the requirements of the Chinese standard for subgrades below Grade II. This study suggests that titanium gypsum has broad application prospects as a stabilizer for expansive soils.