Patch Repair and Macrocell Activity in Concrete Structures

For many years, electrochemical potential mapping has been the most commonly used technique for assessment of steel corrosion in concrete structures. Because electrochemical potentials are affected by a number of factors, however, a proper interpretation of potential mapping requires much experience. In this paper, it is shown how a combination of potential mapping with electrical resistance mapping can reduce both difficulties and uncertainties in the interpretation of potential mappings. By combining net potential differences with concrete resistivities and depths of concrete cover, corrosion activity maps can be made to visualize the effect of patch repairs on macrocell activity of localized corrosion on embedded steel. In addition to providing a very good image for assessment of localized corrosion, it is also shown how the severity of corrosion can be expressed by histograms based on all of the single measurements of galvanic activity.