On site monitoring of concrete reinforcement corrosion

Reinforcement corrosion is the result of the penetration through the concrete cover of the carbon dioxide (carbonation) and of chlorides. It is not a usual event in nuclear plants due to the relatively short service life required. However, in waste storage facilities with much longer target service life.. it may be one of the most relevant deterioration processes. Therefore. its detection and measurement should be one of the aspects to be taken into account in the overall management of these kind of installations. In present paper, the most usual electrochemical techniques to measure reinforcement corrosion are described. The aims of the application of these techniques is. 1) to control the performance of new constructions (embedded sensors). 2) to detect corroding areas in existing structures (by on-site measurements or by installing external sensors) and implement these values in models to recalculate the structural performance and 3) to control the efficiency of repair techniques. In the paper is as well presented the evolution from 1995 of corrosion parameters (corrosion rate, corrosion potential, electrical resistivity, concrete strains, oxygen availability) obtained in a pilot container buried in real conditions in the repository of El-Carbril-Spain. The results indicate that the temperature is the most relevant variable influencing the measurements. In conclusion: Corrosion of reinforcement can be approximately model and accurately measured on-site. The periodical corrosion rate measurements on its monitoring seems very necessary to assess present conditions of concrete structures and is a very useful tool in the case of cooling towers of power plants. Techniques based in the measurement of Polarization Resistance have been implemented in portable corrosion rate meters to obtain corrosion rate values, and corrosion-data-loggers are now operative in different structures to monitor corrosion related parameters. (authors)