Full-scale mapping of asphalt pavement compaction degree using GPR: A roller-mounted approach

Accurate measurement of asphalt layer compaction degrees is critical during construction. Ground-penetrating radar (GPR) can be installed on a roller for continuous dielectric constant and density measurements of the surface layer during the construction process, providing full-scale mapping of the compaction degree. This could allow on-site fixing of potential under- or over-compaction. However, challenges such as surface moisture from roller nozzle sprays, field data instability, and the need for parameter calibrations in the dielectric constant-density model hinder its application. This study provides a roller-mounted GPR approach to evaluate asphalt surface layer compaction quality on a full scale. The proposed approach addresses the influence of water vapor between the antenna and the ground surface on GPR accuracy, mainly coming from water sprays from the steel roller. The asphalt mixture density statistics were utilized as evaluation metrics for measuring the compaction degree and uniformity. A data stability correction method was developed to eliminate outliers. The dielectric constant-density prediction model was calibrated using laboratory and field core testing results. Case studies based on field validations demonstrate that GPR technology effectively controls the overall compaction density between 94% and 96%. Unmanned compaction machinery exhibited superior compaction uniformity, with a lower coefficient of variation compared to conventional machinery types. Variations in compaction degree were observed at construction section edges and between lanes, highlighting the need for improved construction monitoring for quality assurance.