Performance of a Composite Soil Prepared with Red Mud and Desulfurized Gypsum

Given the great environmental pressure brought by the massive stacking of solid waste, red mud and desulfurized gypsum were used to prepare cementitious materials. In this paper, three different material ratios with a 60% content at different curing ages (7 d, 14 d, and 28 d) were utilized to prepare the composite soil. To explore the performance of the composite soil, the resistivity, strain-stress, unconfined compressive strength, and pH of the composite soil were tested and analyzed, as well as the microscopic properties. The results show that the addition of solid waste can enhance the strength, while the optimal ratio of desulfurized gypsum to red mud is 2:2. The enforcement of strength comes from the hydration products. The main products of composite soil are hydrated calcium silicate gel or hydrated calcium aluminate gel and ettringite. In addition, the composite soils behave like a brittle material with peak stress and softening performance. In addition, the current frequency presents an obvious effect on the resistivity of composite soil, and the data at 50 kHz were recommended as the analytical data. Moreover, a positive connection exists between the strength and resistivity; therefore, the strength can be conveniently and expeditiously observed and predicted through the resistivity method in engineering.