The moisture content and the resistivity of the concrete, respectively, is a decisive parameter of the reinforcement corrosion. Numerous techniques are available for the survey and assessment of reinforced concrete structures. But there is a clear lack of methods for the monitoring of repaired structures. This is especially true in cases where concrete surfaces are protected against further carbonation or chloride ingress by means of low permeable or even electrically insulating coatings and potential mapping is not applicable or only with restrictions. In such situations the measurement of the electrical resistance or the resistivity of the concrete might be helpful to trace the change of the moisture content after the rehabilitation and to judge about the success of a repair. In this paper the overwhelming effect of the resistivity of concrete (moisture content) on the corrosion process is discussed as well as the main influences on the resistivity of concrete. Further a survey of on-site measuring techniques of the concrete resistivity is presented together with some practical examples.
