Asphalt Concrete Pavement Evaluation with GPR: A Case Study of Layer Thickness Validation and Density Prediction

Ground-penetrating radar (GPR) is at the forefront of nondestructive pavement evaluation techniques in the US, with common applications for pavements’ subsurface and surface investigations. Radar systems are effective in-depth estimation provided accurate dielectric constant is known. In this study, GPR is used for a thorough evaluation of seven different full-depth asphalt concrete (AC) segments at Illinois Certification and Research Track in Trenton, IL. The track includes three stone-matrix asphalt and four dense graded hot-mix asphalt segments with different surface characteristics namely, variation in texture and roughness. The track also includes embedded copper plates at different depths to validate GPR systems. A GPR system mounted on a vehicle was used to collect data at three different vehicular speeds (5, 10, and 20 mph). The evaluation focused on accurately estimating the dielectric constant for the different layers using their reflection amplitudes after various signal corrections. The dielectric constants are then used to predict layer thickness, AC density, and estimate depth of copper plates. The predicted results were compared to design thicknesses, core densities, and as-built copper plates layout, respectively. The results illustrate the importance of GPR signal processing and the power of GPR as a reliable evaluation tool for AC pavements.