Enhanced mechanical properties and mechanism of iron ore tailings-based geopolymers modified by municipal solid waste incineration fly ash

Iron ore tailings, coal fly ash and municipal solid waste incineration fly ash (MSWI FA), as solid waste, must be disposed of. Iron ore tailings, coal fly ash and MSWI FA were successfully prepared into high-performance geopolymer. The compressive strength of optimal geopolymer reached 57.89 MPa. Based on XRD, FTIR, SEM and chemical extraction analysis, C-(A)-S-H was the main gel product along with N-A-S-H. It was found that the dominant hydration process of geopolymer was changed from diffusion process (D) to phase boundary reaction process (I) after MSWI FA addition based on hydration reaction rate curves and dynamic simulation, releasing more hydration heat and generating more C(N)-A-S-H gels. Heavy metal content in the optimal geopolymer was below the limits of Class I screening value of development land (GB 36600-2018). Ef and Cf of the optimal geopolymer were 30.9 MJ/ton/MPa and 6.88 kg CO2/ton/MPa, affirming the viability of utilizing iron ore tailings, coal fly ash and MSWI FA as raw materials for geopolymer production, which provides a promising collaborative resource method of processing them.