Non-saturated Chloride Diffusion in Sustainable Cementitious Materials

Abstract

Chloride-induced reinforcement corrosion, caused by chloride diffusion in the unsaturated concrete cover, is a major durability problem of concrete structures. Current concepts for concrete mixture design and for service life prediction are generally based on the understanding of the chloride diffusion coefficient of saturated concrete. This will introduce uncertainties and give rise to misjudgement of the actual serviceability of concrete structures, especially when supplementary cementitious materials (SCMs) are added in the concrete mixture. This thesis developed a numerical tool for predicting the chloride diffusion coefficient in cementitious materials at different degrees of water saturation. The tool accounts for the microstructure and moisture distribution in cementitious materials. The tool provided a basis for service life design based on unsaturated chloride diffusion. The results of the thesis emphasize the importance of looking at the chloride diffusion coefficient at unsaturated state, rather than at saturated state, in order to more effectively utilize the SCMs in concrete mixture design.