Improved Corrosion Inspection Procedures for Reinforced Concrete Bridges: Electrical Resistivity of Concrete

Abstract

The effects of steel reinforcement and chloride-induced corrosion initiation on the electrical resistivity measurements using the Wenner probe technique were studied experimentally on custom-designed reinforced concrete slabs. Investigation parameters included (1) probe configurations with respect to rebar mesh, (2) rebar density, (3) epoxy coating on the rebar, (4) concrete cover thickness over embedded reinforcement, (5) chloride ingress, and (6) corrosion of rebar. The concrete moisture condition and cover thickness influenced the effect of rebar mesh. It was theorized that bound chlorides increased electrical resistivity measurements and counteracted the effect of free chlorides. It was observed that epoxy coated rebar did not significantly affect measurements. Uncoated rebar affected resistivity measurements, particularly for saturated and semi-saturated concrete. Corrosion initiation was observed to have no significant effect on measurements. Larger concrete cover thicknesses provided for more discrepancy between half-cell potential and electrical resistivity measurements. Recommendations to increase electrical resistivity measurement accuracy on reinforced concrete slab surfaces are made.