The potential field measurement is routinely used for the assessment of the corrosion distribution on reinforced concrete structures. The method can easily be applied, however, the potential is influenced by numerous factors. The concrete humidity, the pH-value in the concrete, the oxygen content, and the electrical resistance strongly influence the determined values.
Based on theoretical considerations and on the so far successfully performed experiments, it can be expected that the corrosion potential can be separated from the overlapping potential drop. This effect will be investigated under well-defined laboratory conditions and on real structures. Artefacts caused by e.g. the diffusion over potential of the reference electrode and their effects on the result will also be considered.
The theoretical background and the limits of the new technique will be evaluated, the reliability will be checked and the directives for the application and interpretation through the engineer will be set up. Interpretation problems in the damage assessment, as they occur with wet or carbonated structures could be eliminated.
The disadvantages of the potential mapping shall be compensated.
At laboratory test potential gradient to be created on the concrete surface by means of defined incorporated spat Sener currents. This can be done by voltage drop, the correlation and corrosion stove under defined conditions. The diffusion overvoltage may affect the measurement of potential on concrete bodies. Measurements should therefore be carried out at various surface conditions such as carbonation, moisture gradients and concrete quality.
Based on the insights gained as the adaptation of existing measurement infrastructure is possible. In addition, it should be possible by the installation of a measuring point at a new building under real conditions to control measurements. This is achieved by an experimental setup that allows the injection of artificial streams and control of real corrosion currents.
The research project was aimed at improving interpretation of the results of the potential field measurement. The higher reliability of the measurement, more accurate damage assessment is made possible. This makes possible a more accurate assessment of the damage situation and an optimized concrete removal during repair. Upon successful course of the project the foundations for the detection of corrosion rate could be elaborated in a follow-up project.
For the practical application it may be concluded that the measuring procedure used so far is suitable. In order to localize small corrosion sites at homogeneous humidity distribution it may be necessary to apply an especially fine measuring grid. However, the reliability of the technique might not be given, when the heterogeneous humidity and/or chloride distribution has been removed. This is especially the case with repaired concrete structures where the chloride contaminated concrete was removed and replaced by a new concrete cover.