Influence of Mineral Admixture in CSA Cement on Chloride Binding Capacity

Abstract

Increasing chloride binding capacity of hardened cement paste is an effective method in reducing corrosion risk of reinforcement in concrete structures exposed to marine environment and guarantee its designed service life. Compared with traditional Portland Cement, Calcium Sulfoaluminate Cement (CSA) has been proved for its better chloride binding capacity in practice. However, in order to save cement consumption and reduce environmental pollution, it is important to investigate the influence of mineral admixture on the Cl− binding capacity of CSA cement. Based on this background, authors of this paper studied influence of key parameters within CSA-Cl− mix proportion, i.e. mixtures like Calcium carbonate (C), Slag (S), Fly ash (F) and Metakaolin (M) and use of gypsum and studied its effect on the chloride binding capacity. Meanwhile, the Cl− binding mechanism was also explored by means of XRD and TG. From the results obtained, it can be concluded that the use of gypsum led to an increase in ettringite, which caused a severe drop in chloride binding capacity; the addition of mixtures led to an increase in chloride binding capacity.