Impact of confinement condition of dynamic modulus test on the performance of flexible pavement structures

This study investigates the impact of confinement on the dynamic modulus (|E*|) of asphalt concrete (AC) mixtures, a key indicator correlated with their field performance of asphalt pavements. Confined |E*| testing is crucial for assessing the expected performance of both conventional and modified AC mixtures. The primary aim of this study was to evaluate how confining pressure affects the |E*| values of AC mixtures and subsequent impact on simulated performance of three different types of asphalt pavement structures (thin, thick, and composite) through changes in typical distresses and corresponding service life. Utilizing the AASHTOWare Pavement ME Design software, 48 different pavement sections were simulated under both unconfined and confined conditions. The simulated performance scenarios included the investigation of two different AC mixtures, dense and gap-graded, under three different climate conditions, cold, moderate, and warm. The findings revealed significant variations in pavement performance, especially notable in gap-graded AC mixtures across all climates, with service life differences of up to 45% and marked changes in resistance to rutting, fatigue cracking, and International Roughness Index (IRI). In contrast, dense-graded AC mixtures demonstrated less sensitivity to confinement, with less than 10% variations, highlighting the critical role of tailored confinement in laboratory testing to simulate real-world pavement behavior more accurately. This research underscores the relevance of confinement in laboratory testing of |E*| to enhance the accuracy and reliability of pavement design, ensuring better alignment with actual field performance, ultimately increasing the cost effectiveness of maintenance and rehabilitation.