| Abstract | The complex frequency-dependent impedance of the interface between concrete and reinforcing steel bars (rebar) can be indirectly measured using a four-electrode array on the surface of the concrete. Impedances were measured at several corrosion rates, which that were simulated by anodic polarization at specific currents, and at different corrosion extents, which were simulated by the accumulation of corrosion products after the application of fixed currents for various time periods. The measured impedances changed consistently with the change in the corrosion states in the 0.01 to 1000 Hz band. The results are in agreement with those obtained using standard electrochemical impedance spectroscopy (EIS), but the present method has three significant advantages: i1) no contact need be made with the reinforcing bar; ii2) the measurement is specific to the small portion of the rebarreinforcing bar beneath the measurement array, ; and iii3) because the time constant of the impedance relaxation spectrum depends on the area of rebarreinforcing bar involved, the frequencies are higher than those needed when direct contact methods are used (thus reducing measurement time). It appears that the surface measurement is a powerful method to study the corrosion process, both in the laboratory and in the field. |
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