Mechanical, expansion and rheological properties of circulating fluidized bed fly ash based ecological cement: A critical review

Circulating fluidized bed fly ash (CFBFA) is a solid waste product from circulating fluidized bed (CFB) boilers in power plants, and the storage of CFBFA is increasingly become an environmental problem. Previous scholars have made contributions to improve the resource utilization of CFBFA. Especially, ecological cement is prepared by CFBFA, which is more conducive to its large-scale utilization. In recent years, a lot of effort has been paid to improve the properties of ecological cement containing CFBFA. In this work, the physicochemical properties of CFBFA are introduced, and recent research progress on the mechanical, expansion, and rheological properties of CFBFA based ecological cement (CEC) is extensively reviewed. The problem of over- expansion of f-CaO is summarized, which limits the scale application of CFBFA in ecological cement. Hence, the challenge for f-CaO in CFBFA to compensate for cement volume shrinkage is proposed, which is beneficial to the utilization of CFBFA in ecological cement, and the reduction of CO₂ emissions from the cement industry. In addition, the environmental performance, durability, and economy of CEC should be valued in future research, especially the environmental performance, because the CFBFA contains heavy metals, such as Cr, As, which may pollute groundwater.