Concrete Inspection - Interpretation of Potential and Resistivity Measurements

The development of a laboratory model of a linear reinforcing bar with defined anode and segmented cathode areas is described. The polarisation characteristics of the passive and corroding areas on these model bars when cast into a range of concretes were measured and used as input data for a finite element model of the corroding steel in concrete system. Finite element calculations are described that investigated the effects of varying concrete resistivity and concrete surface condition on the measured surface potentials and the current at the reinforcing bar. The finite element model is shown to give results that are in good agreement with experimental results obtained on the laboratory model linear reinforcing bar cast into cylindrical concrete samples. The finite element model was then extended to allow calculations to be performed on three dimensional systems. The results of potential and resistivity surveys on two real structures (a water retaining storage tank and a motorway bridge beam) are described and the extended interpretation of the results and assessment of corrosion current discussed. For the covering abstract of the conference see IRRD 831449.