Research on the Mechanism of Calcium-Based Desulfurization Ash Stabilizer for Soft Soil

Desulfurization ash is a solid waste generated during the flue gas desulfurization process in the steel industry. Currently, if left untreated, it can pose environmental hazards. The desulfurization ash from semi-dry sintering (SDDA) in this study was used as the primary raw material to prepare a composite stabilizer suitable for soft soil stabilization. The stabilizer formulations with varying SDDA content were designed, and the engineering performance and ecological safety of the stabilized soft soils were comprehensively evaluated. The results indicated that when the SDDA content in the stabilizer was 20%, the 7-day unconfined compressive strength (UCS) reached 0.803 MPa; when the desulfurization ash content was 30%, the 28-day strength reached a maximum of 1.154 MPa. After stabilization, the concentrations of heavy metals such as manganese and chromium in the stabilized soft soil were far below the limits set by relevant national soil pollution risk control standards, indicating that this stabilization system might reduce the migration risk of heavy metals into the environment. Microscopic mechanism analysis revealed that the sulfur-containing components in SDDA promoted the formation of ettringite, while the alkaline environment it provided activated the cementitious system—comprising cement clinker and mineral powder—thereby facilitating the formation of calcium silicate hydrate gel. This study provided a feasible technical approach for the large-scale resource utilization of semi-dry desulfurization ash.