Study on the solidification mechanism and durability of copper and cadmium contaminated soil stabilized by red...

To achieve green remediation of heavy metal-contaminated soils and promote the resource utilization of industrial solid wastes, this study employed red mud and calcium carbide slag as partial substitutes for cement to prepare a composite curing agent (PCRC) for the stabilization of copper and cadmium contaminated soils. Unconfined compressive strength, toxicity leaching, freeze-thaw, and wet-dry cycle tests were conducted to evaluate the mechanical properties, stabilization efficiency, and durability of the treated soils. Furthermore, SEM, XRD, FTIR, MIP were used to elucidate the microstructural solidification mechanisms. The results indicate that when the PCRC dosage was 8% and the mixing ratio of cement: red mud: calcium carbide slag was 4:4.5:1.5, the 28-day strength of the specimens reached 523.8 kPa, while the leaching concentrations of copper and cadmium were far below the regulatory limits. Even after multiple freeze-thaw and wet-dry cycles, the samples maintained satisfactory performance. Microstructural analyses revealed that hydration products such as C-S-H, C-A-H, and ettringite stabilized and immobilized heavy metals through mechanisms including pore filling, adsorption-encapsulation, and precipitation. These findings provide theoretical and technical support for the remediation of contaminated soils and the resource utilization of solid wastes, achieving the goal of "treating waste with waste" while reducing costs and enhancing efficiency.