Effect of temperature on transport of chloride ions in concrete

Abstract

Chloride-induced corrosion is the major durability issue of reinforced concrete structures along seacoast and in cold areas where de-icing salts are used. Various service life prediction models based on chloride induced corrosion have been developed. Temperature plays an important role in modeling chloride transport in cement-based materials. However, it is often overlooked. In this paper, the effect of temperature on non-steady-state migration and diffusion coefficients of chloride ion in concrete with water-to-cement ratios of 0.35, 0.48 and 0.6 were investigated. Non-steady-state migration coefficient was measured at 20°C adn 5°C following NT build 492. Non-steady-state diffusion coefficient was measured at 5°C, 20°C and 40°C according to NT build 443. The effect of temperature on migration/diffusion coefficient is examined by using Arrhenius Equation. The results show that higher temperatures result in higher diffusion/migration coefficients. Temperatures alter the chloride penetration depth, but not the trend of chloride profile. The activation energy obtained from non-steady-state migration coefficient is quite comparable to Samson and Marchand’s results (Cement and Concrete Research, V37, 2007, 455-468), which is around 20 kJ/mol, and independent of water-to-cement ratio. However, the activation energy obtained from non-steady-state diffusion tests ranges from 17.9 to 39.9 kJ/mol, which seems dependent on water-to-cement ratio. The surface chloride concentration is also affected by water-to-cement ratio and temperature.