Experimental Study on Strength Characteristics of Expansive Soil Improved by Steel Slag Powder and Cement Under Dry–Wet Cycles

Expansive soil, as an unsaturated cohesive soil, is considered a harmful geological soil due to its tendency to expand with water and shrink with loss of water. Especially in the alternating environment between dry and wet (D–W) cycles, it can cause engineering accidents because of its deformation. Steel slag powder (SSP) was used as a new curing agent to improve the expansive soil by combining cement. The variation rules of strength characteristics of improved expansive soil were studied under the condition of the D–W cycles. Through the laboratory test, the unconfined compressive strength (UCS) characteristics of the expansive soil (ES) and improved expansive soil (improved by cement (Es-C) and by steel slag powder and cement (Es-SSP-C) and by steel slag powder and cement and NaOH (Es-SSP-C-N)) were studied under different curing age and different D–W cycles. The testing results show that the strength of improved expansive soils increases with the curing time. The strength degradation of Es-SSP-C-N samples was the least when they have performed the D–W cycles, which indicates that Es-SSP-C-N is a good method to improve expansive soil in the D–W circulation environment.