Diffusion of chloride ions from seawater into concrete

Abstract

The rates of chloride diffusion from seawater into concrete made with different w/c ratios and different types of cements were studied. The effect of cathodic protection on the chloride penetration was also investigated. The effect of w/c ratio on the chloride content was limited mainly to a surface layer of the concrete and to short durations of exposure. For longer durations of exposure and for greater depths of penetration, cement type had a greater influence on the depth of chloride penetration than the w/c ratio. Portland cements gave as much as two to five times higher chloride penetration than blended cements. For the Portland cements as much as 8.6% C 3A was not adequate for reducing the chloride penetration compared with zero-content of C 3A. It appears that the diffusion of chloride ions into concrete is dependent not only on the permeability and the capacity of chloride binding but also on the ion exchange capacity of the system.