Circulating fluidized bed fly ash-blast furnace slag based cementitious materials: Hydration behaviors and performance

Circulating fluidized bed fly ash (CFA) is a byproduct that is discharged by circulating fluidized bed (CFB) boilers in coal-fired power plants. CFA is hard to be utilized on a large scale in cementitious materials because it contains many unstable components (SO3 and f-CaO). This work aims to increase the utilization ratio of CFA in cementitious materials under the utilization of f-CaO and SO3. In this work, the proportion of CFA in CFA-based low clinker cementitious materials (CCM) is increased to 40 wt% (CCM40), and the mix of cement clinker is only 30 wt%. The main hydration products are C-S-H gel, C-A-S-H gel, and ettringite, which are helpful to the performance development in CCM. Furthermore, the high polymerization of [SiO4] and compact microtopography are reflected in CCM40. The concentrations of heavy metals leaching in CCM40 are the lowest, which meets the drinking water requirements of the World Health Organization (WHO). Therefore, this article offers a novel idea about the large-scale utilization of CFA in cement, and makes the CFA less pollution to the environment.