Pretreatment of Municipal Solid Waste Incineration Bottom Ash for Utilization in Magnesium Oxysulfate Cement

The utilization of municipal solid waste incineration bottom ash (MSW-IBA) as a resource is critical to achieving its potential social and environmental benefits. This study investigated the effects of MSW-IBA and its finely ground powder (MSW-IBAP) as fine aggregates and mineral admixtures on the mechanical strength, hydration product composition, and microstructure of magnesium oxysulfate cement (MOSc). These properties were characterized through mechanical strength testing, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The results demonstrated that MOSc prepared with preaged MSW-IBAP (treated with 4 mol/L NaOH at 20% content as an admixture) exhibited an optimized microstructure and hydration product composition [Mg(OH)2 to 5·1·7 phase ratio], resulting in superior mechanical properties. In addition, the preaging treatment of MSW-IBAP facilitated the formation of M-S-H gel–like hydration products, significantly improving the water resistance of MOSc. The use of MSW-IBA as both a mineral admixture and fine aggregate in MOSc provides notable technical and economic advantages. Furthermore, this approach offers a novel pathway for the resource utilization of MSW-IBA, contributing to substantial social and environmental benefits.