Influence of Sulfates on Chloride Diffusion and Chloride-Induced Reinforcement Corrosion in Limestone Cement Materials at Low Temperature

Abstract

An ordinary portland cement and two portland limestone cements [15 and 35% weight-to-weight ratio (w/w) limestone content] were used for concrete and reinforced mortar specimens preparation. The specimens were exposed to two corrosive solutions (chloride sulfate and chloride) at 5°C. Total (acid-soluble) and free (water-soluble) chloride contents, and apparent chloride diffusion coefficients, were determined in concrete specimens. Reinforcement corrosion half-potential and current density, mass loss of steel rebars, and carbonation depth were measured in mortar specimens. Limestone cements showed very good behavior, although the environments were very corrosive. Total and free chloride ions concentration increased with exposure time and limestone content. Limestone cements showed less capability of binding chlorides than pure portland cement. The cement with low limestone content was the most effective in preventing reinforcement corrosion during mortar exposure to the combined chloride-sulfate solution, although it allowed the most intensive corrosion in the case of the chloride-bearing solution. The presence of sulfates led to higher chloride ion concentrations, less chloride binding and, generally, higher values of chloride diffusion coefficient, and also promoted reinforcement corrosion to a greater extent. Low temperature conditions retained a relatively low corrosion rate.