This study also investigated thermal stress relaxation of asphalt mixtures based on a limited number of asphalt samples tested. Using the Crack Sealing Machine, cooling and relaxation experiments were carried out at different rates, isothermal temperatures, and isothermal relaxation times. For all experiment thermal stress was observed to build up as the temperature decreased in the restrained beam.
Temperature reduction was stopped at a predefined temperature to start the isothermal stage. Although the temperature measured at the core of the asphalt sample was kept constant, the sample stress continued to build up even after the core temperature had stabilized. Isothermal contraction was also observed simultaneously in the unrestrained beam of Crack Sealing Machine.
As the is othermal conditioning continued, the Crack Sealing Machine stress gradually started to relax. This trend was observed for all asphalt mixture samples tested. It is observed that after the initial isothermal stress buildup, the rate of buildup, the rate of build-up gradually decreases, followed by a relaxation of stress until stabilizing at a constant value over time.
