Calcium oxychloride: A critical review of the literature surrounding the formation, deterioration, testing procedures, and recommended mitigation techniques

Deicing salts have long been known to cause deterioration in concrete pavements. Freeze/thaw, surface scaling, and reinforcement corrosion are well documented deterioration mechanisms. However, another mechanism exists causing severe concrete damage that is much less understood. This deterioration is due to the formation of calcium oxychloride, from chemical interactions between the cementitious paste and certain chloride-based deicing salts. The basic chemical structure of calcium oxychloride, with slight variations, has been reported in deteriorated samples. Ideas have been postulated about failure mechanisms associated with the formation of calcium oxychloride. Further, testing techniques such as thermogravimetric analysis, low-temperature differential scanning calorimetry, and volume change measurements have been successfully utilized to better understand/quantify calcium oxychloride. Mitigation techniques to minimize the impact of calcium oxychloride include reducing cement content through the use of supplementary cementitious materials or other means, the use of adequate air entrainment, preferential carbonation, and the use of concrete sealants. This review of the literature highlights the current understanding of calcium oxychloride, provides best practice guidance and identifies new areas of research needed in order to effectively mitigate calcium oxychloride damage in concrete pavements.