Utilization of CO2 from a Carbon Capture Plant for Curing Alkali-Activated Low-Reactivity Fly Ash

Abstract

Nowadays, the carbon dioxide (CO₂) capture and utilization for curing alkali-activated materials offer a promising pathway for both CO₂ sequestration and the production of low-carbon construction materials. However, low-reactive fly ash (FA), which is an easily accessible and widely available industrial byproduct, poses basic challenges due to its poor reactivity under conventional curing conditions. In this research, the utilization of CO₂ generated from a pilot-scale carbon capture plant at RKDF University, Bhopal, is investigated to cure alkali-activated low-reactive FA pastes. The curing process is carried out at 40 °C and 0.5 bar gauge pressure for durations of 6, 12, and 24 hours. Mass monitoring, compressive strength testing, X-ray diffraction (XRD), and efflorescence assessment are employed to evaluate the performance. The experimental results show that after 24 hours of CO₂ curing, the pastes achieved a CO₂ uptake of 12.4% by mass of FA. After 28 days, a compressive strength of 42.6 MPa is found, which is approximately 50% higher than that of ambient-cured controls. Efflorescence is nearly eliminated due to the conversion of free alkalis into insoluble carbonates. XRD analysis confirmed the formation of calcite (CaCO₃) as the primary carbonation product, while quartz and mullite remained inert. This research experimentally shows that CO₂ from a carbon capture plant can effectively upgrade low-reactive FA into a high-strength, durable material, offering benefits of waste valorization, CO₂ storage, and utilization.