Factors influencing chloride transport in concrete structures exposed to marine environments

The present study concerns a literature review regarding chloride transport in terms of the diffusion coefficient (D) and surface chloride content (CS) in concrete structures exposed to a marine environment. In addition, a refined model is proposed for D and CS for time-dependent chloride transport. It is found that both D and CS are time-dependent: D decreases and CS increases with time, due to further cement hydration development. D and CS are significantly influenced by concrete mix proportion, air void content in concrete, curing methods, degree of exposure to seawater and climate. Blended cement concretes are beneficial in decreasing D, but increase CS, presumably due to a refinement of the concrete pore structures and chloride binding. An increase in the air void content in concrete increases D, but decreases CS. The CS depends on curing methods such as water, membrane and aeration. The degree of exposure to seawater does not have a clear relationship with CS: higher exposure levels did not result in a higher level of CS. Exposure in tropical areas results in higher CS in concrete jetty structures with a similar level of D, mainly due to an increased temperature and concentration of salinity. Based on these findings, a refined model for CS was proposed to provide more realistic prediction of the build-up of chlorides by chloride transport in concrete structures exposed to marine environments.