Evaluating Performance of Ground Penetrating Radar (GPR) and Pachometers for Bridge Deck Reinforcing Steel Cover Height Verification

Bridge deck deterioration, especially corrosion of its reinforcing steel, could largely limit the bridge capacity, durability, overall safety, and daily operation during the routine service of the bridge system. However, it is a challenge for inspecting the actual condition of the bridge deck, as the progression of in-service bridge deck deterioration is usually hidden from observation. Therefore, a proper inspection method is important for preventive maintenance and rehabilitation of reinforced concrete. Currently, transportation officials commonly choose non-destructive testing (NDT) methods because they allow inspectors to detect the distribution of deterioration or the cover thicknesses without damaging the bridge deck surface. Ground penetrating radar (GPR) and pachometer are two NDT methods mainly applied to measure the concrete thicknesses and reinforcing steel cover heights. This paper will introduce the GPR and pachometer in detail, discuss the advantages and limitations of each, and determine their accuracy in measuring cover thickness based on data collected from three bridges in Kentucky. The result shows the GPR processed with multiple ground truth points can achieve better accuracy in steel height measurement in general, but the pachometer also has some advantages such as its cost-effective design. This paper aims to provide a practical reference for both state transportation agencies and contractors to select the proper device to improve the inspection of bridge decks.