Failure of Exposed Concrete Caused by Corrosion of Embedded Steel

Abstract

Concrete in various forms has been employed as a durable and economical building material since ancient Roman times. Since concrete is relatively weak in tension, contemporary concrete construction usually requires the addition of reinforcing steel to augment its flexural and tensile strength. Fortunately, a chemical characteristic of concrete helps it to protect embedded reinforcing steel from corrosion by providing a highly alkaline environment. Certain conditions, however, can affect concrete’s protective chemistry or can attack the steel in other ways. When the reinforcing steel rusts, oxidation byproducts, or rust scale, expand and create tensile stress in the adjacent concrete. Cracking and spalling of the adjacent concrete is often the first symptom of this underlying steel corrosion ~Fig. 1!.