Numerical and Experimental Development of Gradient Potential Measurement for Corrosion Detection in Reinforced Concrete

Half-cell potential mapping is commonly used to detect corrosion risks in Civil Engineering structures. This method uses a reference electrode positioned on the surface of concrete for measuring potential difference by using a voltmeter connected to the reinforcement bar. However, there are two major drawbacks in the implementation of this method: the electrical connection to the reinforcement and its electrical continuity. In order to overcome these disadvantages, a new method is proposed. Instead of using electrical connection to rebar, a second reference electrode is used, also positioned on the surface. These two electrodes configuration result in electrical potential gradient on the concrete surface. By performing both experimental work and numerical modelling, this configuration is tested. For experimental work, two reinforced concrete slabs (3x3x0.15 m) were casted to be close to actual structural conditions. Then corroded areas with controlled sizes are created through a specific device allowing chloride migration. The thickness of the concrete cover has an influence on the measures, which is why the first slab includes rebar where the cover is fixed, while it is variable in the second slab. For modelling, a parametric study using a finite element model is performed. This model allows the study of the influence of several parameters such as resistivity, corroded area size, concrete cover, and also the measurement process. It is the analysis of the corrosion current, as well as potential mapping that allows the correlation between the experimental and modelling results. Discussion of both results concludes feasibility of this method and confirms its benefits compared to usual half-cell potential mapping.