Resistance of Concretes to External Chlorides in the Presence and Absence of Sulphates: A Review

Corrosion of steel reinforcement due to chloride attack remains a major reinforced concrete durability concern. The problem is prevalent for concrete structures located within marine environments or frost-prone locations where chlorides containing de-icing salts are used. This paper is a state-of-the-art review into chloride binding in Portland cement concrete, with consideration of the differences induced by the presence of sulphates, such as found in seawater. The review also considers the use of supplementary cementitious materials (SCMs), the use of which has increased because of their potential to enhance durability and reduce the carbon footprint of concrete production. Such materials impact on phase assemblage and microstructure, affecting chloride binding and transport properties. Therefore, field and laboratory studies are critically reviewed to understand how these could help in the design of more durable concretes. The contributions of chloride binding, hydrate compositions and microstructures of the binding materials affecting chloride transport in concretes are also evaluated to suggest a more robust approach for controlling the problem of chloride attack.