Obtaining Effective Half-Cell Potential Measurements in Reinforced Concrete Structures

Corrosion of steel reinforcement is a major factor in the deterioration of highway and bridge infrastructure. A survey of the condition of a reinforced concrete structure is the first step towards its rehabilitation. A rapid, cost-effective and non-destructive condition survey offers key information on the evaluation of corrosion, and aids in the quality assurance of concrete repair and rehabilitation and in the prediction of remaining service life. Half-Cell Potential Measurement The simplest way to assess the severity of steel corrosion is to measure the corrosion potential, since it is qualitatively associated with the steel corrosion rate. One can measure the potential difference between a standard portable half-cell, normally a copper/ copper sulphate (Cu/CuSO4) standard reference electrode placed on the surface of the concrete with the steel reinforcement underneath. Figure 1 illustrates the basics for such a measurement, also called half-cell potential measurement. The reference electrode is connected to the positive end of the voltmeter and the steel reinforcement to the negative. Confidence in the half-cell potential measurement as an indication of corrosion potential has evolved owing to the success of bridge deck corrosion surveys. An indication of the relative probability of corrosion activity was empirically obtained through measurements during the 1970s.[1-2] This work formed the basis of the ASTM standard C876, which provides general guidelines for evaluating corrosion in concrete structures as outlined in Table 1.