Valorization of municipal solid waste incineration fly ash in low-carbon alkali-activated materials

Municipal solid waste incineration fly ash (MSWIFA) is a hazardous waste with high alkalinity and is rich in heavy metals (HMs) and chlorine. To facilitate resource disposal, this paper proposes recycle MSWIFA as an alkali activator to develop low-carbon and cement-free alkali-activated materials. The designed MSWIFA-activated slag exhibited impressive compressive strength (>70 MPa). The microstructure of the MSWIFA-activated slags was tightly filled with various reaction products, including ettringite, calcium aluminosilicate hydrate (C-A-S-H), and Friedel’s salt. The leaching behaviors of the HMs and chlorine were significantly restricted owing to the chemical fixation of the reaction products and the dense microstructure of the MSWIFA-activated slags. The immobilization of chlorine primarily depended on the formation of Friedel’s salt, and the remaining chlorine could be captured by the positively charged sites of C-A-S-H. The reaction mechanism of the designed MSWIFA-activated slags could be divided into three stages: ettringite precipitation, C-A-S-H formation, and Friedel’s salt generation. This paper provides constructive insights into the resource utilization of hazardous waste and contributes to the development of low-carbon alkali-activated materials.