Towards a two-step assessment of the chloride ingress behaviour of new cementitious binders

Abstract

A wide range of systems were exposed to a seawater-like chloride concentration (0.5 M Cl⁻) for bulk diffusion experiments over 0.5, 1 and 4 years. Combined with previously published findings on chloride binding and mini-migration testing, the results showed that chloride ingress into saturated blended cement pastes is a diffusion-governed process, obeying the square root-law or a modified version including an offset to account for slow microstructure changes. Chloride ingress is also strongly correlated with bulk electrical conductivity, suggesting a negligible effect of chloride binding variations between the systems studied. These findings support a two-step approach to rapidly characterise the chloride ingress behaviour of new binders at the cement paste scale. A screening with bulk conductivity measurements investigates promising binders and the kinetics of their diffusion properties. In a second step, bulk diffusion tests and the square root law with an offset are used to predict chloride ingress.