Corrosion assessment of epoxy coated reinforcement in concrete structures

钢筋混凝土结构是我们基础设施的重要组成部分。当受到氯离子腐蚀的影响时，如果维护不当，这些结构的使用寿命就会缩短。除了传统的黑钢加固外，环氧涂层钢筋(ECR)在北美尤其被用作防止氯离子引起的钢筋腐蚀的一种措施。目前，德国对环氧涂层加固的批准正在进行中。然而，不能保证涂层是无缺陷的。不能排除涂层缺陷中的腐蚀过程，但由于运输过程受到限制，导致的腐蚀速度是有限的。如果我们想要从环氧涂层加固的优势中获益，就需要一个如何对这些结构进行检测的科学依据。因此，有必要特别努力地开发和应用精确和准确的腐蚀检测方法。不可靠的检测数据可能会导致不必要的修复操作，甚至可能导致对腐蚀钢筋进行不必要的修复操作的情况。所有正在研究的电化学测量方法(腐蚀电位、极化电阻、电化学阻抗谱、零阻安培计)在处理、工作量、空间信息(栅格或点阵测量)、可靠性等方面都有优缺点。这些优势和劣势将被总结和讨论。其目的是将测量技术结合在一起，使一种测量技术的缺点可以由另一种测量技术来补偿，以实现更高的检查可靠性。根据检查问题(缺陷检测或腐蚀活性检测)，将制定检查指南，考虑所产生的可靠电化学检查方法的组合、范围和顺序。最后，将预先确定的检测方法和检测程序应用于既有的环氧涂层钢筋混凝土结构。在欧洲，只有上述两座桥梁含有环氧涂层钢筋，因此数据库相当有限。在美国，超过65,000座桥梁结构使用环氧涂层钢筋进行防腐。因此，为了从ECR结构检测的知识中获益，为了进一步开展腐蚀状况评估，与美国的专家合作是必要的。

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.