Application of electrical fields to reduce chloride ingress into concrete structures

Abstract

In the context of a joint research project, a system for monitoring, protection and strengthening of bridges by using a textile reinforced concrete interlayer has been developed; the system consists of two carbon layers with a spacing of 15 mm and a special mortar. This setup led to the idea of building up an electrical field between the carbon meshes, to suppress the ingress of chlorides into the concrete. This paper focuses on the question of which voltages and electrical field strengths are necessary to prevent critical chloride contents at the reinforcing steel. For this purpose, extensive laboratory tests have been performed, followed by a numerical simulation study. By applying an electrical field, the negatively charged chloride ions are forced to move to the upper carbon mesh, which is polarised as an anode. It has been investigated whether the voltages to implement an electrochemical chloride barrier are smaller than they have to be for the common preventive cathodic protection. One advantage of this chloride barrier is that, because of the lower current densities, the anodic polarisation of the carbon meshes can be reduced. Therefore, different voltages, electrical field strengths, anode materials and anode arrangements were investigated.