Comparison of thermal stresses calculated from asphalt binder and asphalt mixture creep tests

Low-temperature cracking is a significant distress in asphalt pavements built in the northern United States and Canada. As temperature decreases, thermal stresses develop in the restrained asphalt surface layer; and when the temperature reaches a critical temperature, cracking occurs. The current guides use thermal stress as a critical input parameter in the low-temperature performance model. In this paper, statistical and graphical analyses are performed to compare thermal stresses that develop in an idealized asphalt pavement calculated from mixture creep data obtained using indirect tensile test (IDT) and bending beam rheometer (BBR) test. In addition, the idea of obtaining thermal stresses from binder BBR creep data is further investigated. Thermal stresses calculated using IDT and BBR mixture creep data, respectively, are similar. Thermal stresses calculated from binder creep data are significantly different than thermal stresses calculated from mixture creep data. The effect of physical hardening is investigated for a limited number of materials, and the effect on thermal stresses is significant.