Modelling analysis of chloride redistribution in sea-sand concrete exposed to atmospheric environment

Abstract

The combined effects of external carbonation and internal chloride transport are the main reasons leading to the degradation of concrete structures manufactured with sea sand. To evaluate the degradation process of sea-sand concrete structures, a mathematical model for describing the redistribution of internal chlorides in sea-sand concrete exposed to atmospheric carbonation was proposed in this study. In the proposed model, changes in porosity, saturation degree, and the release of bound chlorides under the carbonation were considered. The numerical simulation of proposed model was executed by COMSOL software in a concrete model generated with random aggregates, which is verified to fit well with the experimental data obtained from a case study. In the modelling results, the chloride concentration in pore solution was decreased with the deeper depth after redistribution. However, on the chloride profile with the unit of wt% of concrete, a ‘pseudo enrichment’ of chlorides content was found after chloride redistribution and verified to be caused by the unit conversion. In conclusion, the proposed model could be used to predict the service life of sea-sand concrete structures exposed to atmospheric environment.