Utilization of pretreated municipal solid waste incineration fly ash for cement-stabilized soil

In this study, the feasibility of using municipal solid waste incineration fly ash (MSWIFA) as additive for the strengthening of pretreated cement-stabilized soil was evaluated. Results indicated that the leaching concentrations of chromium and lead in MSWIFA after the water washing process and addition of 4% ferrous sulphate were reduced by 67% and 89%, respectively, which was lower than the limit value of Identification standard for hazardous waste (GB 5085.3-2007). After pretreatment, MSWIFA samples with ratios of 5% and 10% were blended into cement-stabilized soil with ordinary Portland cement (OPC) content of 10%, 15% and 20%. The unconfined compressive strength (UCS), internal friction angle and cohesion of the cement-stabilized soil increased with OPC and pretreated MSWIFA (PFA) content. The same effect was observed on UCS after the addition of 10% PFA as replacement of 5% OPC. In the subsequent X-ray powder diffraction test, scanning electron microscopy and leaching tests, the leaching concentrations of heavy metals in cement-stabilized soil became far lower than the limit value under the synergistic effects of the physical encapsulation of hydration products and stabilization of chemical agents. The incorporation of PFA as a supplementary material can effectively accelerate the formation of hydration products and can thus provide cleaner options for foundation reinforcement.