Understanding and Detecting Bridge Deck Deterioration with Ground-Penetrating Radar

Properly timed preventive maintenance and rehabilitation can extend the life of a bridge deck and reduce life-cycle costs. To implement such an effort, owners need to decide which decks are in good condition, which need work (and what type of work), and which are not economical to repair and need to be replaced. These decisions require accurate assessment of the subsurface deck condition. Traditional methods to evaluate deck condition are not economically feasible to implement on a large number of structures. Recently, ground-penetrating radar (GPR) has been implemented to scan bridge decks rapidly and to provide the necessary information. However, the relationship between GPR measurements and the state of deck deterioration is not well understood, and thus the full acceptance and adaptation of GPR has been limited. The goal of the work reported in this paper was to establish a clearer connection between the data produced by GPR equipment and the elements and stages of the deterioration process. This goal was advanced by an evaluation of bridge deck slabs, saw-cut out of a heavily deteriorated deck during demolition, and brought into the lab for evaluation. The slabs were subjected to hammer sounding, ultrasonic impact-echo, half-cell potential for corrosion, and multiple ground- and air-coupled GPR systems, which ranged from 1.0 to 2.6 GHz. The paper describes the results of experimental testing and the correlations between the deterioration process, identified through traditional testing and the measured and processed GPR signal responses.