Effect of exposure temperature on chloride-binding capacity of cementing materials

Abstract

Chloride-induced corrosion of reinforcement is one of the main causes of concrete deterioration in marine environments. The service life of reinforced concrete (RC) structures exposed to chloride ions is closely related to the rate of chloride ion diffusion through the concrete. Chloride binding has a remarkable influence on chloride penetration and hence on the time to corrosion initiation in RC structures. Determination of the apparent chloride diffusion coefficient of concrete takes into account the chloride-binding capacity but not the effect of temperature on the chloride-binding capacity. This paper examines the effect of temperature, from −4°C to 70°C, on the chloride-binding capacity of paste mixes containing supplementary cementitious materials (SCMs) as cement replacements. The results of the current study suggest that Friedel's salt formation is the major cause of the reaction between chloride ions and tricalcium aluminate (C3A) and hence the chloride-binding capacity decreases with increasing temperature; the order of chloride-binding capacity as a function of exposure temperature is 22°C > −4°C > 3°C > 35°C > 50°C > 70°C. Both the experimental and modelled results indicate a non-linear relationship between the exposure temperature and the chloride-binding capacity for cement paste containing SCMs as cement replacement.