Hot-mix asphalt (HMA) compaction at longitudinal joints is critical for pavement performance and longevity. Many highway agencies face challenges maintaining deteriorated joints, often resulting in issues like raveling along the centerline. Despite extensive research and training on proper HMA placement and compaction, joint deterioration remains a leading cause of premature flexible pavement failure. Improving joint compaction during construction is critical to better pavement performance. The longitudinal joint construction includes various methods—differing laying conditions, joint geometry, rolling patterns, and techniques. While each has advantages, these methods also carry risks in consistently achieving optimal compaction. Current quality assurance (QA) methods, such as coring and density gauges, are labor-intensive, time-consuming, costly, and offer limited coverage, increasing the likelihood of missing low-density areas. The variability in construction methods and limitations of traditional QA testing raises the risk of inadequate joint compaction, potentially compromising pavement's durability and performance.The Dielectric Profiling System (DPS) offers a nondestructive alternative for assessing compaction quality, providing continuous real-time coverage by measuring dielectric values, which correlate with HMA density but need a calibrated relationship. Adopting DPS for QA testing requires alternative methods (other than air voids) to quickly assess joint density during construction. This study compared various longitudinal joint construction methods using dielectric measurements from Minnesota and Michigan road projects. The continuous dielectric data were discretized into subsections for analyses using relative dielectric differences that indicated over 2% more air voids at the joint than at the mat. This study used a coreless calibration method with lab-prepared pucks to develop a new model for converting dielectric values to predicted air voids for similar analyses. Project- and group-wise calibrations were performed; project-specific models aligned well with cores collected during DPS and QA testing. Minor HMA production fluctuations across different days displayed minimal impact on air void predictions. Additionally, HMA mixtures were grouped for group-wise calibrations using recorded dielectric values and mix characteristics, which demonstrated reasonable accuracy. This approach highlights the potential for direct DPS data use in the field without needing project-specific models. Statistical analyses revealed that unconfined joints had the highest air void content, with 50 to 100% of subsections showing significant differences, indicating over 2% more air voids than the adjacent mat. Additionally, 60 to 100% of unconfined joint subsections fell below the 60% Percent Within Limits (PWL), the rejectable quality level (RQL). In contrast, all other joint types showed similar compaction to the mat, with negligible subsections below 60% PWL. These findings were consistent when using predicted air voids. Similarly, the probabilistic analysis showed a 30 to 60% likelihood that unconfined joints had significantly lower dielectric values than the mat, while other joints exhibited minimal differences or better compaction. This study introduces a Longitudinal Joint Quality Index (LJQI) that enables the direct use of dielectric values to enhance the field applicability of DPS. A threshold of 70% LJQI was established for joint quality acceptance. LJQI comparisons revealed that unconfined joints had higher void content than the adjacent mat in 11 to 89% of stations across multiple projects. According to all the analyses conducted, it was consistently found that constructing either butt or tapered joints while avoiding unconfined joint construction can lead to achieving better joint density. Moreover, it has been observed that smaller subsections are efficient in identifying local compaction problems, and for practical reasons, it is suggested to use 100 ft subsections during analyses. Many State Highway Agencies (SHAs) rely on specifications that focus on as-constructed air voids to assess construction quality and determine pay factors (PF) for contractor payments, often neglecting the performance of longitudinal joints. This study proposes a Performance-Related Specification (PRS) framework that leverages the DPS's continuous data to link joint service life to void content, used as the Acceptance Quality Characteristic (AQC). By using air void content as AQC and PWL quality measure, SHAs can more accurately assess joint quality and make informed pay adjustments, ensuring durable, high-quality pavements while minimizing overpayments.
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