Test methods for on site measurement of resistivity of concrete - a RILEM TC-154 technical recommendation

This paper describes methods to assess concrete resistivity on site for various purposes related to corrosion and protection of reinforcement. It is based on the first draft of a forthcoming RILEM Technical Recommendation. The electrical resistivity of concrete can be related to the two processes involved in corrosion of reinforcement: initiation (chloride penetration) and propagation (corrosion rate). The resistivity of a structure exposed to chloride indicates the risk of early corrosion damage, because a low resistivity is related to rapid chloride penetration and to a high corrosion rate. Once damage has occurred, resistivity is relevant for electrochemical maintenance methods. The resistivity of the cover (near surface) concrete can be measured non-destructively by placing electrodes on the concrete surface, applying a voltage and measuring the current. Several arrangements can be used, one electrode (the reinforcement is the second electrode), two electrodes, and four electrodes. Practical aspects of these arrangements are discussed. Procedures for calibration are proposed. Guidelines for the interpretation and reference values for various exposures and concrete compositions are given. (C) 2001 Elsevier Science Ltd. All rights reserved.