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Corrosion Control in Concrete

Given the importance of the costs associated with the corrosion of infrastructures, it is extremely important that all possible methods applicable to controlling corrosion in existing concrete bridges be developed so that these structures will not deteriorate prematurely. Equally important is developing methods to avoid this costly corrosion problem in all new concrete bridges to be constructed in the future. Accordingly, the control methods can be divided into two major areas:

The use of good construction design and procedures, adequate concrete cover depth, corrosion-inhibiting admixture, and low-permeability concrete alone will not abate the problem, because concrete has a tendency to crack inordinately. Even corrosion-inhibiting admixture for concrete would likely not be of use when the concrete cracked. This situation essentially leaves the reinforcing steel itself as the last line of defense against corrosion. For this very reason, the use of a barrier system on the reinforcing steel, such as epoxy coating or other organic or even other possible metallic coatings, is even more critical in abating this costly corrosion problem.

It is likely that there may never be any organic coating that can hold up to the extreme combination of constant wetting and high temperature and high humidity that reinforcing steel is often exposed to in the marine environments. The many successful performance of embedded epoxy-coated steel bars in different projects indicates that when used in exposure conditions that do not keep the concrete constantly wet, the epoxy coating will provide a certain degree of protection to the steel bars and, thereby, delay the initiation of corrosion.

For existing chloride-contaminated concrete bridge decks, impressed-current cathodic protection using titanium mesh anodes-provides the ultimate and permanent solution to stopping reinforcing steel corrosion in the structures, as long as associated rectifiers and electrical wiring are properly maintained. Electrochemical chloride extraction provides an alternative rehabilitation method for stopping steel corrosion in contaminated concrete, albeit less permanently. This alternative has the advantage of having no rectifier or wiring to maintain after the treatment. (reference)