Formulation and durability of slag/metakaolin-based geopolymers with 70% municipal solid waste incineration fly ash (MSWI FA)

In this study, municipal solid waste incineration fly ash (MSWI FA) was used as an alternative to geopolymers for resource recovery. The 70% MSWI FA mixing and durability of slag-metakaolin based geopolymer was assessed. The optimum formulation was determined based on MSWI FA mixing, silica-aluminum ratio (A), sodium-silica ratio (B), water-solid ratio, and slag content, and the solidification effect was analyzed in terms of compressive strength and heavy metal leaching concentration. The solidified products were tested by acid rain leaching, acid and alkali immersion, high-temperature calcination, and freeze-thaw cycles. The crystalline phases and structures of the solidified products were analyzed for stability using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and Scanning Electron Microscopy (SEM). The experimental results revealed that when the mixing amount of MSWI FA was as high as 70%, the compressive strength of the solidified products under the optimal formulation was 11.97 Mpa, and the solidification rate of heavy metals was greater than 92%. The solidified products also exhibit good durability properties such as acid and alkali resistance, high-temperature resistance, and freeze-thaw resistance. Based on this study, the geopolymer possesses strong MSWI FA treatment capability.