Use of GPR for thickness measurement and quality control of flexible pavements

This paper evaluates the performance of ground penetrating radar (GPR) in estimating the layer thicknesses of flexible pavements. The findings presented are based on field data collected from the Virginia Smart Road's pavement test facility, from a newly built section of a state highway (Route 288, Virginia), and from a section of an in-service interstate highway (I-81). The GPR data collected from the Virginia Smart Road were successfully used to evaluate the physical GPR for flexible pavement layer thickness determination. The data analysis was facilitated by a complete knowledge of the different structures and compositions of the various sections of the road, and by copper plates (perfect electromagnetic reflectors) that were embedded at the different layer interfaces during the construction of the pavement. Based on the collected data, it was found that current GPR analysis approach fails to detect layer interfaces in some circumstances because of physical limitations (such as low dielectric constant contrast between the layers combined with relatively high material loss or the presence of thin layers, compared to the GPS resolution, within the surveyed pavement system). However, GPR is a feasible nondestructive tool for estimating the layer thicknesses of hot mix asphalt (HMA) layers, provided that the appropriate data analysis technique for the type of surveyed pavement is used. For newly constructed pavements, GPS can be successfully used as a quality control/quality assurance tool using simple data acquisition techniques. However, for in-service pavements or pavements composed of multiple thin layers, special data analysis techniques should be applied to achieve reasonable thickness accuracy.