Influence of Chloride in Reinforced Concrete

The present state of knowledge regarding the action of chloride, principally calcium chloride, in reinforced concrete is reviewed, with special emphasis on its effect on the reinforcing steel. The reactions through which calcium chloride accelerates the set and strength of portland cement are explained, as well as the significance these reactions with cement have with regard to the potential corrosion of steel reinforcement in concrete. Calcium chloride's beneficial effects in ordinary reinforced concrete are enumerated, along with the precautions regarding its use in prestressed concrete and special situations. The deterioration of bridge decks and the significance of the “chloride content corrosion threshold” that has been suggested for bridge decks are discussed. It is pointed out that the limit for chloride that has been suggested as a guide to determine the extent of repair to existing bridge decks that have been subject to repeated application of deicer salts is not a requirement that should be applied to limit the chloride content of ordinary reinforced concrete. When the amount of commercial calcium chloride is limited to two percent by weight of cement, the degree of corrosion in ordinary reinforced concrete is insignificant if the concrete is reasonably dense and there is adequate cover over the steel.