Macrocell Corrosion Currents in Simulated Concrete Pore Solution and Reinforced Concrete

Abstract

Chloride-induced rebar corrosion is one of the main causes of damage in reinforced concrete structures (RCS). Chloride attacks lead to depassivation creating pits, which can imply major losses of sections. The current generated at these spots (microcell) is contributed by the current produced between corroded and uncorroded areas (macrocell). The influence of both currents has been deeply investigated based on solution studies, which do not actually represent the behaviour of concrete-embedded elements. The studies about macrocell currents in solution are interesting to analyse this phenomenon quickly and simply. However, they must not be interpreted as the reality of RCS because this requires studies using rebars embedded in concrete. The performed experimental plan verified this fact. In addition, another objective of this study was to analyse the influence of concrete’s electrical resistance and the limiting effect of the cathode/anode surface (Cs/As) ratio on macrocell currents in solution and in concrete. For this study, specimens manufactured using concretes with different properties were used: standard concrete (SC), high-performance concrete (HPC), very high-performance concrete (VHPC) and ultra-high performance-fibre reinforced concrete (UHPFRC). The conclusions show how the Cs/As ratio plays a key role in regulating macrocell current intensity, but what really governs this phenomenon is concrete resistivity because it regulates the participation of a bigger or smaller cathode surface. The influence of this parameter as a limiting factor of macrocell currents is fundamental, especially in high resistivity concretes like VHPC and UHPFRC.