Predicting the atmospheric carbonation of cementitious materials using fully coupled two-phase reactive transport modelling

The durability assessment of cementitious materials and concrete subjected to atmospheric carbonation of concrete has been an extensive study of research. Experimental studies on the subject show, among other results, that the response depends strongly on the cement composition. This paper focuses on two model materials: an hydrated C₃S paste and a low-pH paste, which exhibits a higher tendency to cracking. We show that a fully coupled reactive transport model can reproduce the measured experimental depths of carbonation without a need of fitting parameters. A sensitivity provides insights about the most relevant parameters to accurately model the atmospheric carbonation. Furthermore, results suggest that low-pH cement materials might be inherently less mechanically robust when subjected to atmospheric carbonation, due to a higher C-S-H decalcification rate. This implies that these materials are more likely to develop fractures, which could have implications in the framework of gas or radioactive waste disposal. (authors)