Assessment of Conventional and Engineered Surface Asphalt Mixtures Through Empirical and Fundamental Performance Tests

Many state highway agencies are adopting the balanced mix design (BMD) approach to create pavements that are more durable and sustainable, as it allows for performance testing during mix design. Virginia Department of Transportation (VDOT) has started implementing BMD using Cantabro, indirect tensile cracking test (IDT-CT), and asphalt pavement analyzer (APA) rut test to assess durability, cracking, and rutting performance, respectively. However, further efforts are required to validate whether the chosen tests and their thresholds ensure satisfactory long-term performance. This paper addresses three objectives: (i) comparing the performance of control mixtures designed based on volumetrics and their corresponding BMD mixtures, (ii) investigating the consistency between fundamental and empirical tests in characterizing mixtures, and (iii) assessing correlations between these tests to validate or refine VDOT thresholds. This study evaluated 15 VDOT asphalt mixtures, divided into six groups each containing one control mixture and one or two corresponding BMD mixtures. In addition to empirical tests, the dynamic modulus, cyclic fatigue (CF), and stress sweep rutting (SSR) tests were conducted, and correlations were established aiming to preliminary refine VDOT tests' thresholds. The testing confirmed that almost all BMD mixtures met VDOT's thresholds and the recommended criteria for CF fatigue index parameter (Sapp) and SSR Rutting Strain Index (RSI). Statistical analysis concluded that most BMD mixtures maintained similar or better overall performance. A preliminary analysis across all the mixtures collectively showed a low correlation between Sapp and Cantabro mass loss, no correlation between Sapp and CTIndex, and a moderate correlation between RSI and APA rut depth.