Integrated CO₂ Fixation, Waste Stabilization, and Product Utilization via High-Gravity Carbonation Process Exemplified by Circular Fluidized Bed Fly Ash

The valorization of industrial solid wastes in civil engineering is one of the main routes for enhancing resource cycle toward environmental and social sustainability. In this study, an integrated approach to capturing CO₂ in flue gas and stabilizing solid wastes for utilization as supplementary cementitious material via a high-gravity carbonation (HiGCarb) process was proposed. The fly ash (FA) generated from a circular fluidized bed boiler in the petrochemical industry was used. The effect of different operating parameters on the carbonation conversion was evaluated by the response surface methodology. The maximal carbonation conversion of FA was 77.2% at a rotation speed of 743 rpm and an L/S ratio of 18.9 at 57.3 °C. In addition, the workability, strength development, and durability of the blended cement with different substitution ratios (i.e., 10%, 15%, and 20%) of carbonated FA were evaluated. The results indicated that cement with carbonated FA exhibited superior properties, e.g., initial compressive strength (3400 psi at 7 d in 10% substitution ratio) and durability (autoclave expansion <0.15%) compared to cement with fresh FA. After HiGCarb, the physico-chemical properties of FA were upgraded, e.g., lower heavy-metal leaching and stabilized volume expansion, which were beneficial to usage as green materials in construction engineering.