Longitudinal Joint Quality Assurance: Threshold for Dielectric-Based Index

Abstract

Abstract Compaction quality at longitudinal joints (LJ) is critical for hot-mix asphalt (HMA) pavement durability. Traditional quality assurance (QA) methods, relying on pavement cores, are labor-intensive, time-consuming, costly, and limited in coverage. The Dielectric Profiling System (DPS) offers a non-destructive alternative, providing continuous, real-time compaction assessments via dielectric measurements correlated to HMA density. To maximize broader adoption by resource-limiting agencies, the Longitudinal Joint Quality Index (LJQI) was developed as a dielectric-based metric. Based on limited and unsegmented data, an initial LJQI threshold of 60% was proposed for joint acceptance decisions. This study analyzed segmented DPS data from 40 pavement sections in Minnesota and Michigan, employing percent within limits (PWL) and receiver operating characteristic (ROC) curves to refine the LJQI threshold. While the PWL utilized HMA mix-specific calibrated relationships, the LJQI was based on calibrated models for grouped HMA mixes. Results indicate that a 70% LJQI threshold, using an 8% air void upper specification limit and 0.08 dielectric tolerance, optimally reflects compaction quality. Segmenting data into 100 ft sublots further reduced false positives without compromising accuracy. By refining the LJQI and demonstrating the DPS’s ability to provide efficient, accurate, and non-destructive QA, this study supports improved LJ compaction assessment and reduces reliance on traditional core sampling.