Enhanced cementitious mechanism via synergistic activation of circulating fluidized bed fly ash and red mud under hot‐pressing

Abstract The accumulation of solid waste is a critical issue restricting the clean and efficient development of the energy industry. To further enhance the cementitious properties of solid waste‐based cementitious materials, an unconventional approach (hot‐pressing) was proposed to achieve high strength within a short period. Taking circulating fluidized bed fly ash (CFBFA) and red mud (RM) as primary raw materials, the influences of mixing ratio, hot‐pressing temperature, and holding time on the compressive strength of alkali‐activator‐free cementitious specimens were investigated in this work. Techniques such as X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and industrial CT were employed to analyze the variations in hydration reactions during the hot‐pressing process. Meanwhile, the hydration characteristics of cementitious test blocks under normal temperature and pressure conditions were compared. The results demonstrated that under hot‐pressing conditions, the CFBFA‐RM system achieved a compressive strength of up to 69.75 MPa with a porosity of only 1.53% after just 1 h of hot‐pressing. This significantly promoted the hydration reaction in the CFBFA‐RM system, leading to the formation of more hydration products and a denser material structure. The findings provide new insights for enhancing cementitious performance and further improving the utilization rate of solid wastes such as CFBFA and RM.