Reinforcement corrosion in concrete

ABSTRACT The corrosion of metals in concrete is a multibillion dollar problem which affects the construction, transportation, and many other industries. While much has been written about the problem, and numerous reports have appeared which discuss how this corrosion can be controlled, little has appeared on the mechanism whereby this corrosion occurs. It is well known that highway structures corrode, for the most part, due to the influence of deicing salts or marine enviroments. Relatively little has appeared about the equally severe corrosion problems which occur in buildings and other nonhighway structures. Most of these structures are not exposed to the salts present in highway structures, yet they still corrode. It has been observed since the last two decades that reinforced concrete structures deteriorate. The main and common cause of this has been determined as the presence of ions of chloride on the reinforcing steel under the concrete cover. Corrosion of reinforcing steel developes only and when the inherent protection of concrete decays (carbonation) and/or the passivating layer around the steel getting punctured by the chloride ions. The rate of development of this mechanism gets higher and higher in the structures that were designed and/or constructed with a view of strength for concrete only, taking the durability aspects aside. It has now been widely accepted that durability aspects should be given priority with consideration of service conditions and life, before the strength of the structure, to sustain and maintain it under the service loads and the environment. This search discusses how all forms of concrete and similiar cementitious environments protect embedded metals. It also presents evidence to explain how, and why, corrosion occurs in these structures, even in the absence of deicing salts, marine environments, or other salt sources. Factors leading to corrosion in reinforcing elements in concrete, with proposed solution and measures for protection against corrosion and for repairing concrete structures with corroded steel elements. Keywords : Reinforcing Concrete, Steel, Reinforcement Corrosion, Service Life, Strength XI