Study on the Solidification/Stabilization of MSWI Fly Ash by Composite Alkali-Activated Cementitious Materials

Municipal solid waste incineration (MSWI) fly ash (FA) is a hazardous waste produced during the incineration of municipal solid waste, posing a risk of heavy metal leaching and threatening the environment. Therefore, the harmless treatment of MSWI FA has become a crucial issue in environmental safety treatment. This study utilized blast furnace slag, FA, and MSWI FA to prepare composite alkali-activated cementitious materials for the solidification and stabilization of heavy metals in MSWI FA. The results showed that when the MSWI FA content was 30%, the water glass modulus was 1.0, the liquid–solid ratio was 0.32, the initial 24 h curing temperature was 45 °C, and the compressive strength of the solidified body reached 41.9 MPa, demonstrating excellent mechanical properties. Additionally, the leaching concentration and nonresidual state of heavy metals (Pb, Cd, and Cu) reduced significantly. Along with XRD, FTIR, and SEM-EDS analyses, it was revealed that the immobilization mechanism of heavy metals in the solidified body primarily involved physical encapsulation and chemical bonding.