Preparing high-strength ceramsite from ferronickel slag and municipal solid waste incineration fly ash

This study investigated the feasibility of preparing ceramsites from ferronickel slag and municipal solid waste incineration (MSWI) fly ash by evaluating the effect of adding MSWI fly ash on the phase and microstructure transformations and properties of ceramsites. The theoretical calculations indicated that when the addition of MSWI fly ash ranges from 10 wt% to 60 wt%, the main phases in the system are diopside, feldspar, forsterite and merwinite, all of which contribute to the improvement of ceramsites properties. The TG-DSC, XRD and SEM analyses revealed that the initial phase of ferronickel slag and MSWI fly ash can be transformed into ceramsite phases during the roasting process. Specifically, forsterite and enstatite produced by the decomposition of olivine in ferronickel slag will react with calcium oxide produced by the decomposition of fly ash to form diopside and merwinite. Additionally, the reaction product will gradually change from diopside to merwinite as the MSWI fly ash addition increases. An excellent ceramsite with the cylindrical compressive strength significantly exceeding the requirements of high strength lightweight aggregates could be obtained by roasting the ferronickel slag with addition of 20 wt% MSWI fly ash at 800 °C for pre-roasting 15 min and 1275 °C for roasting 20 min, demonstrating its remarkable application prospects in concrete.