Accelerated mineral carbonation curing of cement paste for CO₂ sequestration and enhanced properties of blended calcium silicate

The mineral carbonation (MC) curing of cement-based materials could be employed to obtain both CO₂ sequestration and accelerated strength gain. But there is still absence of understanding on the gas-solid reaction kinetics and mechanisms. This study aims to improve the understanding of gas-solid reaction between CO₂ and cement-based materials during the MC curing, and evaluate the feasibility of blending calcium silicate (CS) as intensified addition. Based on the accelerated carbonation experiments, the impact of different factors (pressure, temperature and water-to-binder rate) on the reaction rate and the CO₂ uptake were systematically investigated. The MC curing showed significant diffusion-controlled kinetics and the reaction gradually turned into the stable product-layer diffusion controlling process. The evolution process of kinetics indicated the increasingly dense structure of cement matrix, as verified by SEM analysis. The blended CS was found to significantly enhance the reaction rate and CO₂ uptake capacity, accompanied with the intensified carbonation conversion of cement components. The increased Klinkenberg permeability of blended CS paste after MC curing demonstrated the diluted effect of CS. In terms of the practical feasibility, MC curing also contributed remarkably to the compressive performance improvement of cement paste with blended CS.