Rheological Characterization of Unmodified and Modified Bitumen in the Temperature Range of 40–70 °C

The multiple stress creep and recovery have been used to quantify the rutting behavior of the binder. The parameter such as non-recoverable creep compliance, percentage recovery, and retardation time depends on the temperature. The sensitivity of these parameters with the variation in the temperature is studied. This experimental investigation is carried out using one unmodified and one modified binder, and the test was carried out at unaged and short-term aged condition. The temperature regime of interest for this study is 40–70 °C. Multiple stress creep and recovery (MSCR) and steady shear tests were performed. MSCR tests were conducted using parallel plate geometry at 40, 50, 60, and 70 °C. The tests were conducted for two stress levels of 0.1 and 3.2 kPa. The steady shear viscosity at two different shear rates was also measured at these temperatures. The creep and recovery response of the bitumen at two different stress levels was found to be scalable, and Burgers’ model was used to predict the creep and recovery response of the bitumen. The Arrhenius constant for different binders and different aging conditions was determined using the viscosity data obtained from the steady shear test. The material functions such as creep compliance, percentage recovery, and retardation time were determined based on the experimental and model results. These parameters were observed to follow Arrhenius relationship in the temperature range of 40–70 °C.