Mechanical Properties and Performance of Mixtures with the Same Volumetric Classification

This study investigates the variations in performance among mixtures that are designed for use with the same traffic classification and whether a single mixture class index-volumetrics relationship (IVR) can be applied to all mixtures within that classification. Three surface mixtures, which are intended to serve traffic levels of 3-30 million equivalent single axle loads, were sourced from different regions in North Carolina: the coast; Piedmont; and the mountains. Dynamic modulus, cyclic fatigue, and stress sweep rutting tests were conducted using the asphalt mixture performance tester. Pavement performance simulations were performed using AASHTOWare Pavement ME Design for fatigue cracking predictions and FlexPAVE (TM) for permanent deformation predictions. The findings indicate substantial differences in mechanical properties, performance indices, and pavement performance among the mixtures despite having similar volumetric properties. The study also shows that an IVR calibrated for a mixture cannot be used to predict the performance of other mixtures within the same mixture classification as the tested mixture. This research highlights the need for restructuring the mixture classification system so that it is based on mixture performance rather than on volumetric design, with the ultimate goal being a performance-based or related specification to eliminate the limitations introduced by the use of volumetric properties.