Performance deterioration of municipal solid waste incineration fly ash-based geopolymer under sulfuric acid attack

This study assessed the durability of the geopolymer arranged from red mud-slag activated by carbide slagmunicipal solid waste incineration fly ash (CRMG) as heavy metal solidification and stabilization binder exposed to sulfuric acid solution. Ordinary Portland cement (OPC) as control group. CRMG and OPC samples were immersed in solutions at pH = 3 and pH = 7 for 112 days. The sulfuric acid resistance of the samples was evaluated through visual observation, weight changes, compressive strength, as well as XRD, SEM, DTG, and FTIR. The results showed that CRMG had a higher acid buffering capacity than OPC in terms of visual appearance and mass loss. The compressive strength of CRMG slightly increased during the initial stage of immersion due to the production of geopolymer gel and the filling effect of a small amount of ettringite and gypsum, but decreased after 7 days due to the formation of a large amount of ettringite and gypsum which induce serious expansion and server cracking. CRMG's compressive strength remained higher than OPC's after 112 days of exposure to the acid solution, with a 20% loss in compressive strength. The leaching concentration of CRMG was far lower than the national standard. The study's conclusions could help reduce the environmental risks associated with solid waste disposal and provide a theoretical framework for the use of MSWI fly ash based geopolymer.