Mechanistic Study of γ-C ₂ S Carbonation with CO ₂ in an Aqueous Environment via Reactive Molecular Dynamics

Cement-based materials are ideal candidates for CO 2 sequestration. γ-Dicalcium silicate (γ-C 2 S) is a primary carbonation-reactive mineral in these materials and exhibits significant CO 2 sequestration potential. In this study, a reactive molecular dynamics simulation method is employed to investigate the fundamental carbonation mechanisms of γ-C 2 S with CO 2 in an aqueous environment. The results indicate that γ-C 2 S shows excellent carbonation reactivity under various CO 2 densities and temperatures. Specifically, the CO 2 consumption rate exceeds 90% under all studied conditions. During the initial stage, the CO 2 consumption rate increases with the elevated temperature, but this temperature dependence becomes less pronounced at a later stage. Additionally, the CO 2 conversion is found to be highly relevant to the H 2 O consumption. It can be concluded that the pivotal reaction mechanisms of the γ-C 2 S–CO 2 –H 2 O system involve the polarization of CO 2 and H 2 O molecules on the γ-C 2 S surface, followed by the gradual conversion of CO 2 into carbonates via proton transfer mediated by H 2 O or OH. Furthermore, a layer of hydration products is formed at the interface, which exerts a negative effect on the carbonation process of γ-C 2 S. The new atomistic insights obtained from the present research provide a scientific basis for improving the efficiency of CO 2 sequestration and promoting the valorization of industrial solid waste.