Environmental Risk Assessment of Aerated Concrete Prepared by Synergistic Utilization of Incineration Fly Ash and Multi-Source Solid Wastes
This study systematically evaluates the environmental risks associated with the resource utilization of municipal solid waste incineration (MSWI) fly ash in the production of aerated concrete, co-prepared with multiple solid wastes. The focus is on the leaching behavior and total content of heavy metals (Cr, Pb, Cd, Cu, Zn) under CO2 curing and chelating agent stabilization. Water washing pretreatment parameters (liquid-to-solid ratio, washing time, ash-to-slag ratio) were optimized for chloride removal. Results demonstrate that CO2 curing suppresses the leaching of most metals; leaching concentrations of Cr, Pb, Cd, and Zn decrease with reduced fly ash content, whereas Cu leaching increases when fly ash is absent. The addition of 17.5% organic sulfur stabilizer (DTC) significantly outperforms inorganic sulfide (Na2S) in immobilizing heavy metals, achieving compliance with national standards without compromising compressive strength or carbon sequestration. Water washing effectively reduces soluble chloride content to below 1% (mass fraction), meeting the HJ 1134-2020 regulatory limit. Optimal parameters include a liquid-to-solid ratio of 5, washing time of 20 min, and a raw material ratio of incineration bottom slag:fly ash:slag = 40:20:40. Under these conditions, the final product exhibits a compressive strength of 1.50 MPa, with heavy metals and soluble chlorides fully compliant. This work provides key technical support for the safe recycling of MSWI fly ash in building materials.