Chloride penetration resistance and chloride binding capacity under different application environments of ferroaluminate cement

Free chloride is a crucial factor that threatens the long-term performance of marine concrete structures. The resistance of cement to chloride penetration and its capacity to bind chloride are important parameters for assessing the ability of cement-based materials to resist chloride in-vasion. Ferroaluminate cement (FAC) has considerable application potential in concrete used for marine structures; however, its resistance to chloride invasion and mechanism of chloride binding have not yet been revealed. In this study, the chloride diffusion coefficient and chloride binding capacity of FAC, for both internal and external chloride ions, are experimentally investigated and compared with that of ordinary Portland cement (OPC). The results show that the chloride diffusion coefficient of FAC mortar is approximately 2.5 times lower than that of OPC mortar. FAC exhibits finer overall pore distribution and the number of pores with sizes within 10-100 nm is reduced, which is responsible for its notably lower chloride diffusion coefficient. The chloride binding capacity of FAC to internal chloride ions is slightly lower than that of OPC, and a portion of the chloride ions are chemically bound by reacting with ye'elimite during hydration. The chlorides bound by physical adsorption constitute a dominant portion of the entire bound chloride content. In the case of external chloride ions, the bound chloride content of FAC is lower than that of OPC. The chemical chloride binding capacity of FAC is comparable to that of OPC and the lower physical adsorption capacity for chloride in FAC leads to a weaker chloride binding capacity compared to that of OPC.