Utilization of mechanochemically pretreated municipal solid waste incineration fly ash for supplementary cementitious material

Abstract

With the rapid development of municipal solid waste (MSW) incineration, the effective disposal and recycling utilization of fly ash is attracting increasing attention. The mechanochemical (MC) treatment as a non-thermal method shows good stabilization of heavy metals and degradation of dioxins in fly ash. The inhibition effect and long-term safety of CaSO4, Ca3(PO4)2, NaH2PO4, and composite additives (50 %NaH2PO4 +50 %CaO) as additives for heavy metals stabilization were investigated. The composite additive showed the best inhibitory effect on heavy metals, and the leaching concentration of Cd, Cr, Cu, Ni, Pb, and Zn were decreased by 95.21 %, 46.84 %, 99.42 %, 49.91 %, 99.83 %, and 99.55 %, respectively. In addition, the modification by MC treatment reduced the particle size and increased the specific surface area of fly ash and improved the activity for resource utilization. Therefore, MC treated fly ash is used as supplementary cementitious material (SCM), which will produce a filling effect and pozzolanic effect improving the performance of fly ash concrete blocks. The compressive strength of the MC-treated fly ash concrete blocks curing for 28 days increased by 35.5 % and exceeded 40 MPa, close to OPC’s strength. The concrete block also had a secondary inhibition on potentially toxic elements, making the resource utilization of fly ash more stable and safer. In general, the MC treatment and the utilization of MC-treated fly ash as SCM effectively inhibit the leaching of heavy metals in fly ash, delivering a promising method for green fly ash disposal.