Reliability evaluation of half-cell potential measurement using POD

The detection of corrosion in reinforced concrete structures is one of the primary tasks during inspection. The most common inspection method used is the half-cell potential method. From half-cell potential readings, a judgment is made by allocating investigated structural concrete surfaces to either corrosion detected or corrosion not detected. In this paper, the development of so-called probability of (corrosion) detection (POD) curves is presented. A numerical approach is presented for evaluating the POD in reinforced concrete structures. The probability that a defect, in this case represented by a corroding (anodically acting) area of the reinforcement steel, can be detected was calculated in dependency to electrolytic resistance of concrete, to the concrete cover, and to the grid size chosen for inspection. If parts exposed to different moisture condition are evaluated in one data set, the reliability of corrosion detection can be strongly impaired. If uniformly exposed surfaces are considered, reliable differentiation is possible. The smaller the grid size, the higher the probability that a defect can be detected.