Synergic effects of circulating fluidized bed fly ash-red mud-blast furnace slag in green cementitious materials: Hydration products and environmental performance

Abstract

Circulating fluidized bed fly ash (CFA) is a dusty solid waste containing unstable components (SO3 and f-CaO) and heavy metals from coal-fired power plants, and its comprehensive utilization rate is less than 25 wt%. This research aims to increase the utilization of CFA under the synergy of CFA, red mud (RM) and blast furnace slag (BFS). In this study, CFA-based green cementitious materials (CGM10) are prepared with 10 wt% RM, 30 wt% CFA, 20 wt% BFS, and 40 wt% clinker. The utilization of f-CaO and SO3 from CFA and Na+ from RM is enhanced by alkaline RM in CGM10. Importantly, the f-CaO, SO3, and Na+ in RM are utilized to generate C–S–H gel, ettringite, and N-A-S-H gel, which are conducive to increasing the strength and volume stability in CGM. Hence, the dosage of CFA in the cementitious material is optimized to 30 wt%. The high dense microstructure and excellent Si–Al polymer structure are found in CGM10-28d. In addition, Na, As, Cd, and Hg in CGM10 are well consolidated by the adsorption of gel products and the formation of new minerals, and their leaching results meet the standards of the World Health Organization (WHO). Therefore, this work provides a feasible reference for the resource utilization of CFA, RM and BFS to prepare green cementitious materials.