Nondestructive full coverage asphalt stripping detection using 3D radar

Since subsurface stripping extent is important for maintaining the road network, Minnesota Department of Transportation (MnDOT) uses forensic measures such as coring. The destructive nature and lack of coverage provided by this accepted method makes finding nondestructive methods for detecting stripping of in situ asphalt pavements an important need for MnDOT and many other agencies. Stripping between hot mix asphalt layers can cause premature failure of pavements. Knowledge of the lateral location, depth and extent of stripping can affect the timing and type of pavement preservation, maintenance, or rehabilitation. This paper reports on use of a DX1821 antenna to collect data at a frequency step of 20 MHz ranging from 50 MHz to 3050 MHz with a dwell time of 7.52 μs using a GeoScope Mk IV control unit on a full-scale asphalt pavement constructed at the National Center for Asphalt Technology (NCAT) test track with built-in stripping. Signals from the known stripped and non-stripped locations were used to evaluate statistical and energy based approaches. It is shown that a maximum energy ratio method an approach that has been successfully applied to acoustic emission applications in the past, can improve signal clarity for stripping detection using ground penetrating radar (GPR). These results are confirmed using highway speed measurements at the Minnesota Road Research Facility with core validation.