Polarization resistance measurements in large concrete specimens: mathematical solution for a unidirectional current distribution

The numerous cases of failure of concrete structures due to the corrosion of steel reinforcements increase the need to find an appropriate non-destructive technique to be used on-site for measuring the degradation rate of the rebars. Although corrosion potential mapping has been used, this technique has been shown to give only qualitative indications of the corrosion risk. In this paper, a preliminary attempt to apply the Polarization Resistance (Rp) method in large structures is presented. This method has proved to be a fast and quantitative technique in laboratory experiments. Assuming the model of 'transmission line', the distribution of the polarizing potential applied from a small counter electrode and the current flow are mathematically calculated. Three possibilities are given in order to calculate the true Polarization Resistance, Rp: (a) the apparent polarization resistance method; (b) the attenuation of potential method, and (c) the two counters method. Finally, the results of applying these equations to beams, fabricated in order to check the validity of the theory, are given. The agreement found confirms the promise of the model chosen.