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

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%.