Influence of porosity network on the chemo-mechanical evolution of low-pH cementitious materials subjected to calcareous attack

This paper presents a study which aims to understand the degradation mechanisms induced in a low-pH cementitious matrix by a calcareous attack and then, to evaluate the porosity network influence on the degradation scenario. To reach these goals, three experimental campaigns were carried out in parallel. Hardened low-pH cement paste samples were made in laboratory-controlled conditions, then immersed in calcareous water containing a small amount of water. Concrete samples were then cast in industrial conditions, cured in a controlled environment, then immersed in the same experimental device. Finally, massive concrete blocks were cast and cured outside with industrial processes before immersion in the attack water. Chemo-mechanical characterizations (SEM, µCT, micro/nano-indentation) were performed to estimate the degradation state of the samples. Geochemical modelling was performed to validate experimental observations. Calcium and magnesium enrichment are the main phenomena in all cases. However, the degradation scenario changes with the curing protocol. Porosity closing is observed in samples cured in a controlled environment, whereas industrial curing conditions induce non-negligible chemical alteration due to a skin effect.