The accuracy of ground penetrating radar surveys for predicting corrosion damage in reinforced concrete decks has improved dramatically over the past 10 years. These improvements have occurred largely due to corrections for depth-related effects and the use of more complex models to represent the movement of radar signals through the concrete. GPR surveys are a valuable component in a toolbox of condition evaluation methods available to maintenance engineers. Unlike visual inspection, the method is not limited to detecting surface indicators of damage, but is instead used to non-destructively probe the interior of the deck system to locate defects and local excesses of moisture and chloride which cause signal amplitude losses. The survey results are typically used to produce a plan view map indicating the location and extent of probable corrosion damage. While GPR alone can provide highly accurate results on unpaved decks, a multimodal approach using two or more condition evaluation methods best provides a conservative estimate of corrosion damage on paved decks. The GPR results are used to reject repair candidates that are in good condition, and to prioritize others for further condition evaluation and repair. The locations delineated by GPR for both sound concrete and probable corrosion damage are used to focus addition investigation using traditional methods such as the chain drag, half-cell potential and coring surveys. The combined analysis of all results provides less variability in estimating repairs, allowing the selection of the appropriate repair method before tendering the work and providing better control on repair pricing and costs.
