Understanding the Sensitivity of Mixture Cracking Performance Tests to Binder Properties and Long-Term Aging

The asphalt community is focused on the paradigm shift in mixture design from volumetrics to an optimization procedure based on performance tests called balanced mixture design (BMD). Laboratory performance tests are being assessed for their relationship to binder properties and field performance. However, existing BMD practice does not account for long-term oven aging (LTOA). This gap limits the appropriateness of thresholds and the potential of BMD for improving pavement performance. The Federal Highway Administration’s Asphalt Materials Research Program has launched a three-phase study to provide insights into relevant performance testing. Phase I compared seven cracking performance tests after short-term aging, whereas Phase II evaluated the sensitivity of selected performance tests to LTOA. Phase III, in which seven loose mixtures collected from Montana, Vermont, Ohio, and Florida were subjected to LTOA, is presented in this paper. The indirect tensile cracking, Illinois Flexibility Index, dynamic modulus, and cyclic fatigue tests were employed before and after two proposed LTOA conditioning protocols. Additionally, chemical, rheological, and fracture properties were obtained from extracted binders to obtain a better understanding of the impact of binder properties on mixture performance indices. Results illustrate that LTOA is critical for a comprehensive BMD framework and, thus, some of the testing protocols, indices, and thresholds need to be refined further.