Materials and Methods for Corrosion Control of Reinforced and Prestressed Concrete St

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Materials and Methods for Corrosion Control of Reinforced and Prestressed Concrete Structures in New Construction

Author: J.L. Smith and Y.P. Virmani | Size: 0.38 MB | Format: PDF | Publisher: FHWA | Year: 2000 | pages: 76

Salt-induced reinforcing steel corrosion in concrete bridges has undoubtedly be come a considerable economic burden to many State and local transportation agencies. Since the iron in the steel has a nat ural tendency to revert eventually to its most stable oxide state, this problem will, unfortunately, still be with us, but to a much lesser degree due to the use of various corrosion protection strategies currently used in new construction. The adoption of corr osion protection measures in new construction, such as the use of good design and construction practices, adequate concrete co ver depth, low-permeability concrete, corrosion inhibitors, and coated reinforcing steel is significantly reducing the occurren ce of reinforcing steel corrosion in new bridges. Because concrete has a tendency to crack, the use of good design and constructi on practices, adequate concrete cover depth, corrosion-inhibiting admixtures, and low- permeability concrete alone will not a bate the problem. Even corrosion-inhibiting admixtures for concrete would probably not be of use when the concrete is crack ed. This situation essentially leaves the reinforcing steel itself as the last line of defense against corrosion, and the use of a barrier system on the reinforcing steel, such as epoxy coating, another organic coating, or metallic coatings, is even more c ritical. It is likely that there may never be any organic coating that can withstand the extreme combination of constant wetting and high temperature and high humidity that reinforcing steel is exposed to in some mari ne environments. Either steel bars coated with a sufficiently stable metallic coating or some type of corrosion-resistant solid metal bars would have to be used. There are some very convincing reports of good corrosion-resistance performance shown by epoxy -coated steel bars in concrete bridge decks where the concrete does not remain constantly wet and other exposure conditions are not as severe. Recent improvements to the epoxy coating specifications and the tightening of requirements on the prop er storage and handling of epoxy-coated reinforcing steel at construction sites will ensure good corrosion protection. For construction of new prestressed concrete bridge members (where for structur al or other considerations epoxy-coated strands cannot be used), the use of a corrosion-inhibitor admixture in the conc rete or in the grout, in conjunction with good construction designs and practices, would provide adequate corrosion protection . However, the long-term effectiveness of all commercial inhibitor admixtures has not been fully verified

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