Comparison of electromagnetic non-destructive evaluation techniques for the monitoring of chloride ingress in cover concrete

The principal cause of the deterioration in reinforced concrete bridges is damage resulting from steel corrosion. Over time aggressive agents, particularly chlorides, are transported through the protective cover concrete layer to the reinforcement causing depassivation of the steel, corrosion propagation and eventual loss of structural integrity. This paper focuses on the use of non-destructive electromagnetic evaluation techniques to monitor the ingress of water and chlorides into cover concrete. The studied electromagnetic parameters are DC-resistivity and relative permittivity, both being sensitive to volumetric water content and chloride content. Results from a study performed on controlled concrete slabs are presented and the capacity of three in-situ techniques to assess the salinity and ingress of electrolytes into concrete is compared.