Durability and heavy metals long-term stability of alkali-activated sintered municipal solid waste incineration fly ash concrete in acidic environments

Municipal solid waste incineration fly ash (MSWI FA) with soluble salts, heavy metal, and persistent organic pollutants, is categorized as hazardous waste. In order to promote the high-value utilization of fly ash, the durability of alkali activated sintered MSWI FA concrete (AASFA) in acid solutions with different pH was studied, and the long-term stability of AASFA was evaluated. Through mass loss, relative dynamic modulus of elasticity, damage layer thickness, compressive strength and other tests, it was found that AASFA has excellent corrosion resistance. After 64 days of exposure to acidic solution, the compressive strength loss of AASFA is 62 % of that of ordinary Portland cement concrete (OPCC). Calcite, Friedel's salt, and fibrous silica-calcite in alkali-activated concrete containing sintered MSWI FA mitigated acid corrosion. The rod-shaped sintered MSWI FA served a filling effect, enhancing the compactness of the matrix and reducing the permeability of H+. The alkali-activated system contributed to the solidification of sintered MSWI FA, in which Cr and Cd converted into residual states, comprising 71 % and 56 %, respectively. The first-order reaction/diffusion model (FRDM) efficiently simulated the long-term leaching of heavy metals in an acidic environment, the predicted leaching of Ba, Ca, Cr, Cu, and Ni over 50 years remained within the limit of GB 8978-1996. The STI for sintered MSWI FA and AASFA were 65.51 and 23.58, respectively, showing that alkali activation enhanced the stabilization of heavy metals in sintered MSWI FA and reduced danger to natural ecosystems.