Abstract
This paper demonstrates that ground-penetrating radar (GPR) is an effective tool for quality assurance and quality control during flexible pavement compaction and after construction. Density is one of the most important properties of asphalt concrete layers in flexible pavement. It is critical to monitor the change in asphalt concrete density during compaction; GPR can be used to measure asphalt mixture density nondestructively and rapidly. However, it is challenging to apply the GPR method during compaction because of the unknown effect of roller-sprayed water on the GPR signal. This paper presents the results of a study on the effect of surface water on the GPR signal when a 2-GHz antenna is used. It was found that the higher-frequency components of the ultrawide band signal were affected by water; however, the lower-frequency components were not significantly influenced. The process consisted of a band-pass filter with a passing band from 200 to 800 MHz and extracting the surface reflection amplitude after filtering. The extracted feature was found to be insensitive to the presence of surface water. Therefore, this technology could be used effectively during the compaction process. Field data collected from two construction projects were used for validating this approach. The proposed approach was found to be feasible for monitoring compaction status. Pavement thickness and density profiles were also obtained by GPR after construction. The density values obtained by GPR were similar to those obtained by nuclear density gauge.