Optimizing Flexible Pavement Density during Construction with Closed-Loop GPR Monitoring

Ground-penetrating radar (GPR) has been proven capable of accurately predicting asphalt concrete (AC) thickness and density. These properties are vital for pavement structural integrity. The objective of this study was to monitor AC compaction during construction. Several challenges have been addressed: 1) A GPR system was retrofitted to a roller compactor; 2) An aggregate dielectric constant database was used, in lieu of back-calculating it from extracted cores; 3) An algorithm to overcome GPR’s limited resolution was used to correct for thin layers; and 4) the effects of surface moisture, from compaction drum, are isolated from GPR signal. Three different stone matrix asphalt (SMA) sections were monitored using GPR and their data were analysed. The predicted thicknesses and densities by GPR were compared to ground-truth extracted cores at specific locations. The mean absolute errors for density and SMA thickness prediction are 0.7% and 4mm, respectively.