Abstract
Failures of prestressing and post-tensioning steel caused by hydrogen embrittlement as a consequence of chloride-induced corrosion are well known in the civil engineering field. In order to monitor the occurrence of localised corrosion in concrete structures (viaduct, prestressed concrete cylinder pipes, pre-stressed and post-tensioned structures), the use of a Linear-Continuous-Reference-Electrode (LCRE) has been proposed, claiming that, once a pit starts in any position on the pre-stressed steel, the potential lowers to values typical of active range, giving promptly the evidence of pitting initiation. Since concerns arise about the effectiveness of this system, a multi-reference electrode (MuRE) was proposed and studied, consisting of a series of continuous metallic wires able to measure the potential of carbon steel rebars and tendons. In 2007, four MuRE prototypes were installed on pre-stressed concrete beams; results of potential monitoring performed during the first year are reported. The MuRE system is able to detect and localize the occurrence of chloride-induced corrosion; the potential reading may be interpreted as the average potential weighted on the crossed equipotential surfaces. As a consequence, the length of a single reference electrode wire of the MuRE must be evaluated on the basis of geometry, conductivity and throwing power of localized attack.
