Phenomena and Conditions in Bridge Decks That Confound Ground-Penetrating Radar Data Analysis

Ground-penetrating radar (GPR) has gained a reputation for providing a fast and generally effective means of assessing and prioritizing reinforced concrete bridge deck delamination repairs on a network level. A collaborative research project between Dalhousie University and the Nova Scotia Department of Transportation and Public Works studied the use of GPR for asphalt overlaid reinforced concrete deck condition assessment. In some instances, differences observed between the GPR-based predictions and the actual quantities of necessary repairs resulted in significant costs for deck repair projects studied during this research project. These differences were caused by phenomena and conditions typical of structures in service and may confound the GPR data analysis. These phenomena and conditions include properties and condition of the asphalt concrete overlay, environmental effects pertaining to moisture, deck structure, extent of deterioration, and the method of detecting and delineating repair areas on the exposed deck surface. When these conditions and effects are expected in survey results, GPR can provide a powerful tool for network-level management of deck repairs. This paper provides a discussion of these phenomena and their effects on the resulting GPR surveys.