Reliability of in-situ asphalt concrete density prediction by roller-mounted GPR

Asphalt concrete (AC) density is the dominant performance indicator of in-service flexible pavements. Contractors are often paid based on achieved density through incentive/disincentive schemes, while agencies use density as a key acceptance metric. To enable real-time density monitoring during compaction, a roller-mounted ground-penetrating radar (GPR) prototype was recently developed, including both software and mounting hardware. The system illustrates accurate prediction in both small- and large-scale laboratory tests. In this study, the reliability of roller-mounted GPR is evaluated at three pavement construction projects in Illinois. The projects had different AC mixes, site conditions, and rolling patterns. After advanced signal processing steps, the roller-mounted GPR reported density profile, heatmap, and a progression curve to assist the roller’s operator in enhancing the rolling pattern and controlling number of passes. The final predicted AC densities by the roller-mounted GPR were compared to measurements by a commercially available dielectric profiling system (DPS), nuclear gauges, and extracted cores. Measurement locations were matched using GPS data. Roller-mounted GPR AC density prediction showed a mean absolute error of 0.4% in point-to-point comparison with ground-truth core density, outperforming other nondestructive methods considered in this study.