Multi-Reference-Electrode for Monitoring of Localized Corrosion in Concrete Structures

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 measured by the LCRE 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. Laboratory tests on mortar samples confirmed the effectiveness of the MuRE. FEM analysis was performed to simulate the application of the MuRE to pre-stressed concrete cylinder pipe (PCCP). In 2007, four MuRE prototypes were installed on pre-stressed concrete beams. Results of potential monitoring performed during the first year are reported.