Effect of clinker/Ca(OH)2 external blending on the hydration mechanism of oil shale ash–MSWI FA based cementitious materials

This paper utilized the blast furnace slag (BFS:70 %)–municipal solid waste incineration fly ash (MSWI FA:20 %)–desulfurization gypsum (DFG:10 %) cementitious system as a foundation, with the oil shale ash gradually replacing the BFS to prepare a solid waste quaternary cementitious system. After selecting the optimal ratio, PI 42.5 and Ca(OH)₂ are used as activators to optimize it, and the impact of different activator types and dosages on solid waste gelling systems is studied. The results show PI 42.5 markedly enhances the solid waste-based system's strength. The optimal effect of clinker shifts forward in the later stage of hydration. The strength of CP1 reaches 39.06 MPa, with a 50 % improvement. Ca(OH)₂ led to the formation of many hexagonal plate-like crystals at the early stage, reducing the system's early strength but significantly increasing it at the later hydration stage. The heavy metal leaching results of all groups meet the drinking water quality standard. Microanalysis by XRD, FTIR, TG-DTG, SEM&EDS shows that the addition of PI 42.5 promotes the generation of functional hydration products such as ettringite, C–(A)–S–H and hydrate calcium chloroaluminate (HCC). As the hydration reaction progressed, ettringite production rose, C–S–H converted to C–A–S–H continuously, and the CP1 group has the best effect in the late stage. This study provides new ideas for the synergistic utilization of municipal hazardous wastes and metallurgical solid wastes, aids economy-environment coordination, and provides a theoretical basis for optimizing solid-waste gelling materials.