Corrosion assessment of epoxy coated reinforcement in concrete structures

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Reinforced concrete structures are an essential part of our infrastructure. When affected by chloride induced corrosion, service life of these structures is shortened if not maintained properly. Beside conventional black steel as reinforcement epoxy coated reinforcement (ECR) is used especially in North America as a measure to prevent chloride induced reinforcement corrosion. Currently the approval of epoxy coated reinforcement in Germany is in progress. However, no assurance can be given that the coating is defect-free. Corrosion processes in coating defects cannot be excluded but due to the restricted transport process the resulting corrosion rate is limited. If we want to benefit from the advantages of epoxy coated reinforcement we need a scientific basis how to inspect these structures. So, a special effort is necessary to develop and apply precise and accurate inspection methods for corrosion detection. Unreliable inspection data can lead to unnecessarily executed repair actions or, even worse, can lead to a situation that needed repair action on corroding reinforcement is not performed.All electrochemical measurement method (Corrosion Potential, Polarization Resistance, Electrochemical Impedance Spectroscopy, Zero-Resistance-Ampere-Meter) under investigation have their advantages and disadvantages in handling, effort, spatial information (raster or point measurement), reliability etc.. These advantages and disadvantages will be summarized and discussed. The objective is to combine the measurement techniques in this way that a disadvantage of one measurement technique can be compensated by another with the aim to achieve higher inspection reliability. Depending on the inspection issue (defect detection, or detection of corrosion activity) an inspection guideline will be developed considering the combination, extent and order of the resulting reliable electrochemical inspection methods. Finally the beforehand identified inspection methods and inspection procedure will be validated on existing reinforced concrete structures made of epoxy coated reinforcement.In Europe only the two mentioned bridges contain epoxy coated rebar, so the data base is rather limited. In the United States over 65,000 bridge structures are executed with epoxy-coated reinforcing steel bars for corrosion protection. Therefore, to benefit from the knowledge about inspection of ECR structures and for further development of corrosion condition assessment its essential to cooperate with the experts from the US.