Synergistic Effects of Air Content and Supplementary Cementitious Materials in Reducing Damage Caused by Calcium Oxychloride Formation in Concrete

Abstract

Pavement damage occurs in cold-region concrete exposed to high concentrations of calcium chloride (CaCl2). The damage is caused by a combination of conventional freeze-thaw damage and the formation of a deleterious phase known as calcium oxychloride from a reaction between CaCl2 and calcium hydroxide in the concrete. Much research has focused on calcium oxychloride mitigation in cement pastes, but not on concrete damage due to calcium oxychloride. In this study, the synergistic roles of air and supplementary cementitious materials (SCMs) in reducing damage in concrete exposed to high concentrations of CaCl2 and freeze-thaw conditions is studied. Concrete mixtures were made with different SCM replacement levels and air contents ranging from 1.8 to 8.0% and immersed in 25% CaCl2 solutions and subject to freeze-thaw cycles (-8 °C to 25 °C) for 600 days. Bulk resistivity and visual assessment of damage were found to be excellent descriptors of the damage progression. Damage was reduced as the SCM content and air content was increased. Mixtures which had 20% SCM and 8% air and mixtures which had 35% SCM and more than 4% air showed strong durability against damage due to calcium oxychloride formation.