Half-Cell Potential as an Indicator of Chloride-Induced Rebar Corrosion Initiation in RC

Abstract

The results of an experimental study conducted on specimens similar to ASTM G109 made with different types of cement and steel, and varying water/cement (w/c) ratios are reported in this paper. A portion of the top surface of the specimens was subjected to an exposure to 3% sodium chloride solution followed by an exposure to air, in cycles, for a large number of repetitions. Half-cell potential measurements were carried out periodically at the beginning of every exposure to chloride solution and also just prior to exposure to air, until a sudden drop in the potential was noticed. The average half-cell potential value of top steel bar, after sudden drop, is observed to be nearly the same, irrespective of steel, cement, and w/c ratio. However, corresponding free and total chloride concentrations, just after the preceding sudden drop, varied with experimental factors. The aforementioned sudden drop is also accompanied by reversal in the direction of current between top and bottom steel bars, indicated by a sign change in the potential difference. Thus, it is demonstrated that half-cell potential is a stable indicator of rebar corrosion initiation.