Speaker
Description
Carbonation is a major degradation process affecting cementitious materials, with significant implications for the durability and service life of concrete structures. Under atmospheric exposure, carbon dioxide (CO$_2$) penetrates the partially saturated pore network, dissolves in the pore water, and initially reacts with portlandite (Ca(OH)$_2$) to form calcium carbonate (CaCO$_3$). As carbonation progresses, the calcium silicate hydrate (C-S-H) phase undergoes decalcification, accompanied by further precipitation of calcium carbonate. These coupled chemical reactions lead to pronounced modifications of the mineralogical composition and pore structure of concrete, inducing volumetric shrinkage, changes in transport properties, and the development of internal stresses that promote crack initiation and propagation.
In this study, we present a fully coupled modelling framework that integrates reactive CO$_2$ transport within concrete with a phase-field formulation of fracture. The model explicitly captures the sequential dissolution of portlandite and the progressive decalcification of C-S-H, together with the associated mineralogical transformations and porosity evolution. Shrinkage strains resulting from carbonation-induced reactions are incorporated as driving mechanisms for damage initiation and crack growth. The coupling between chemical degradation, moisture transport, and fracture mechanics enables the description of feedback effects between reaction kinetics, evolving material properties, and mechanical damage.
By providing a mechanistic representation of the interplay between carbonation reactions, pore structure evolution, and fracture processes, the proposed framework offers a predictive tool for assessing carbonation-induced damage and its impact on the long-term durability of cementitious materials exposed to atmospheric conditions.