54 / 2022-03-31 09:08:09

Improvements in probe arrangement and interpretation for non-invasive polarization resistance method

corrosion rate,equivalent circuit model,non-invasive,polarization resistance,probe arrangement

As reinforced concrete structures have been aging in recent years, it is crucial to establish a method to determine the deterioration progress of existing structures. The authors have proposed a non-invasive polarization resistance (NIPR) method for a rebar in concrete. this method can obtain nondestructively an index that is positively correlated with the polarization resistance (PR) of the rebar surface using four probes in a row on the concrete surface, whereas the conventional method requires drilling into the existing structure to connect a connecting wire. However, the equivalent circuit and probe arrangement have not been sufficiently considered in our previous proposals, and it was unclear whether the electrical resistance caused by corrosion could be obtained.

In this study, the equivalent circuit was re-established and the reason for it was presented. In addition, the probe arrangement was changed from an equally spaced arrangement to an outer arrangement (arrangement with the inner 2 probes closer to the outer 2 electrodes), then measurements and current dispersion analysis were performed on the specimens before and after the change.

As a result, it was found that the PR and the concrete resistance can be calculated separately by setting the equivalent circuit appropriately, and that the arrangement change increases the potential response, making it easier to determine the corrosion. This potential increased particularly large when the PR was small. The reason is that, although this method measures the potential difference between the two inner electrodes, current may flow into the rebar outside the measurement range, and this current was larger in the equally spaced arrangement than in the outer spaced arrangement. This study improved the corrosion detection capability of the NIPR method.