ABSTRACT
One predominant type of failure in under-designed asphalt pavements in cold regions is cracking due to low-temperature induced stress. The asphalt binder is the key factor that drives cracking resistance of the asphalt layer. Due to its visco-elastic behavior, the asphalt binder is basically able to relax induced stress, however relaxation capacity is limited at low temperatures. In the frame of performance prediction of asphalt mixtures at low temperature conditions, laboratory relaxation tests are performed to analyze the resistance of a binder sample to thermal cracking. Today’s most common low temperature binder test is a bending test using a Bending Beam Rheometer (BBR). However, BBR testing demands for relatively large amount of binder material. For this reason, in this paper, use of the Dynamic Shear Rheometer (DSR) is proposed to analyze low-temperature relaxation properties. By using a 4-mm parallel-plate geometry, a novel DSR relaxation test procedure is presented for studying low-temperature properties of asphalt binders and corresponding asphalt mastics (combination of asphalt binder and fine aggregates <0.063 mm). The test series includes a set of 10 different asphalt binders and 18 corresponding asphalt mastics. The results of the DSR relaxation tests are also compared to relaxation tests (i. e. Thermal Stress Restrained Specimen Test, TSRST) performed on samples of asphalt mixtures, which were produced of the corresponding material. Finally, the relaxation properties of the asphalt binder, asphalt mastic and asphalt mixture tests are correlated, and the interrelation between these three material scales is determined in terms of a regression analysis.
