Investigation on the effect of cooling medium and aging condition on low-temperature properties of asphalt binder based on BBR

The low-temperature properties of asphalt binder are fundamental for designing asphalt mixture in the cold regions. This is especially true for new technologies such as Warm Mix Asphalt (WMA), for which a reduction in the production temperature may potentially lead to substantial benefits in terms long-term aging. Currently, the specification addressing the low-temperature property of asphalt binder is based on creep tests performed with the Bending Beam Rheometer (BBR) in ethanol. Recently, an alternative experimental method was proposed to conduct the tests in air. In this paper, the effect of cooling medium and aging temperatures on the rheological properties obtained from BBR tests is experimentally investigated and modeled. First, BBR tests are performed in both ethanol and air on four PAV long-term aged asphalt binders, which were previously RTFOT short-term aged at three different temperatures (123 oC, 143 oC, and 163 oC). Then, the creep stiffness, S(t), and m-value are computed. Finally, the Huet model is used to compare the effect of cooling medium and aging temperatures on the rheological model parameters. Results indicate that the reduced production temperature of 40oC significantly affects the material properties at low temperatures, while air leads to higher creep stiffness and poorer relaxation capabilities compared to ethanol.