CO2 carbonation in cementitious systems: a multiscale review based on atomistic simulations

Carbon mineralization in calcium-rich cementitious materials is a promising route to permanent CO 2 sequestration that can simultaneously enhance material performance, yet a unified mechanistic picture spanning length scales is still lacking. This review develops one by integrating density functional theory, classical molecular dynamics, and reactive force-field simulations with experimental observations. Carbonation is analysed sequentially—from CO 2 adsorption and activation at mineral surfaces, through Ca 2+ release and transport in nanoscale pores, to the nucleation, growth, and polymorphic transformation of CaCO 3 —for the principal precursor phases: portlandite, calcium silicate hydrate, and unhydrated clinker minerals. Across these phases, the atomistic evidence converges on a single organising principle: carbonation is governed by the coupling of CO 2 transport, calcium availability, and interfacial reaction kinetics, whose local balance, rather than any single rate, determines the outcome. Carbonation is therefore better regarded as window-controlled than rate-controlled, with the competition between densification and decalcification governing CO 2 -utilization efficiency and long-term performance. This structure–transport–reaction framework links atomistic structure to macroscopic behaviour and provides a mechanistic basis for the rational design of CO 2 -efficient, high-performance cement-based materials.