Improved concrete bridge deck evaluation using GPR by accounting for signal depth–amplitude effects

Ground-penetrating radar (GPR) surveys have tended to provide unpredictable accuracy in estimating areas of corrosion-induced damage in reinforced concrete bridge decks. Six in-service reinforced concrete bridge decks with exposed (unpaved) concrete wearing surfaces were surveyed using GPR to evaluate internal corrosion-induced damage for comparison against the chain drag and half-cell potential survey methods. A normalization procedure for removing GPR signal losses resulting from depth-dependent two-way travel time variations in the data was developed and thresholds for predicting chain-drag and half-cell potential-based estimates of deterioration quantity and location were established. Thresholds established using the amplitude–time correction provided significant improvements in the spatial and quantitative predictive capabilities of GPR for delineating corrosion-induced damage.