A novel microcapsule-based self-healing system was developed in Guangdong Key Laboratory of Durability in Coastal Civil Engineering to prolong the concrete service life, in which lead sulfate is used as the shell material of the microcapsules. The self-healing system is triggered by the reaction of lead sulfate with chloride ion. In this study, the effect of lead sulfate on chloride ion transport in cement-based materials was investigated. The bulk diffusion and rapid chloride migration tests were carried out. The time dependence of chloride diffusion was analysed based on the results of the Bulk diffusion test. The change in the microstructure of cement-based materials upon incorporation of lead sulfate was observed and analysed via mercury intrusion porosimetry and scanning electron microscopy. Results showed that chloride-binding was prevalent at an immersion period of less than 90 days, while sulfate attack superseded after 90 days. Therefore, the impact of both factors needs to be considered when utilizing lead sulfate as a shell material in cementitious materials.

Keywords: Chloride ion, Lead sulfate, Transport, Bulk diffusion, Rapid chloride migration (RCM), Time-dependent diffusion