Influence of carbonation on the chloride ingress into concrete: Theoretical analysis and application to durability design

Abstract

This paper investigates the combined action of carbonation and chloride ingress in concrete under stable moisture state. The chloride profile is solved through a moving boundary problem, assuming a carbonation front, different chloride diffusivities for carbonated and intact zones, and a constant surface concentration. Then, the study performs parameter analysis on the chloride profile, addresses the time-dependence of chloride diffusivity, and applies the model to typical design cases. The results on OPC reference concretes indicate that: (1) the carbonation generally leads to the increase of chloride diffusivity due to the combined effects of pore filling, pore saturation rise and chloride sorption change; (2) the impact of carbonation on chloride diffusion become significant only in low and medium ranges of pore saturation degree; (3) The time dependence of diffusivity is important for durability requirements and the combined action should be considered as the environmental relative humidity is around 60%.