Investigation of High-Frequency Ground-Penetrating Radar for Detecting Debonding of Asphalt Overlays on City Streets

The objective of this research was to investigate the utility of ground-penetrating radar (GPR) as a potential tool for detecting inadequate bonding after placement of asphalt overlays. This research involved field testing of a pavement segment in a city in northern Utah that exhibited inadequate interlayer bonding between the asphalt overlay, which was underlain by paving fabric, and the underlying asphalt. GPR surveys were completed at each of 21 coring locations using 2.6 GHz and 1.6 GHz antennas, and the GPR images were compared to the bond condition determined from the cores. After a careful visual inspection of all of the images, the researchers concluded that no pattern consistently indicated the correct bond condition for either frequency. The absence of a consistent signature indicating either a bonded or debonded condition may be at least partially attributable to the variable texture of the underlying asphalt, where variable void distributions at the interface may cause variable scattering of the GPR signal and thereby mask subtle differences in the interface that would otherwise potentially allow discrimination among bonded and debonded locations.