Corrosion of reinforced and prestressed concrete reinforcements

Abstract

Within the general question of «durability», or chemical resistance of hydraulic cements in the course of time (mortars and reinforced and prestressed concretes), the problem of reinforcement «corrosion» is most important because of its technical and economic significance. This importance is being increasingly appreciated every day, even though corrosion is (or has been) one of the least well known subjects within the field of construction. This importance is evident from the facts themselves, which become clear as a result of the problems that the research laboratories and testing establishments have to deal with. Corrosion is a physicochemical phenomenon which belongs to the ambit of ELECTROCHEMISTRY, and should be studied and evaluated in accordance with the fundamental laws of electrochemistry itself. The same applies to the methods of protection that are to be adopted against corrosion. Corrosion is a chance «risk», and one should seek protection against it by some form of «insurance», represented by the measures to avoid it. The «easiest» cure, from a «technical» point of view, and the «cheapest» from the «economical» aspect, is always a «preventive» one, rather than a «curative» one, i, e., the measures of protection should be taken at the design stage of the structure or work in question. In the case of concrete, the best protection for reinforcements is, in the first place, the adoption of a code of «good practice» in the elaboration of the material and the workmanship, and in the second place, the observance of the most elementary electrochemical principles in the actual matter of corrosion. The use of accelerating additives in the setting and hardening which are of «chlorinated» nature, and the state of «stress» of the reinforcements, are aspects which deserve special interest, as well as the possible electrochemical actions due to «stray currents» travelling through the reinforcements of the structure.