It is very difficult to detect chloride-induced corrosion early, because it is not possible to confirm the degradation of
concrete until cracks induced by corrosion expansion of re-bars appear on the concrete surface. Thus, development of truly non-destructive tests to estimate the chloride content in concrete could make it possible to study the changes in chloride concentration over time, without having to physically approach the structure, or cause any damage to it. Such methods would greatly improve our ability to foresee the possibility of reinforcement corrosion at early stages, and enable us to take the required corrective action at an appropriate time. In this report, in order to evaluate the applicability of non-destructive method which is possible to estimate the chloride content included in cover concrete, the results of theoretical and experimental attempts to estimate the chloride content in cover concrete of the RC structure using the electromagnetic waves are reported.