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The possibility of using the dynamic shear rheometer (DSR) with 4 mm parallel plates and 3 mm gap is investigated as an alternative experimental method to measure the rheological properties of asphalt binders at low temperature. A special butterfly silicone mold was prepared for this purpose and the corresponding testing procedure was also developed. Five different asphalt binders, which are part of two active research projects, were selected. Frequency and temperature sweep tests were conducted using the DSR with three plate–plate geometries: 4 mm, 8 mm, and 25 mm. The new testing procedure was used to measure at low temperatures. The method recently proposed by the Western Research Institute and based on DSR tests with 4 mm parallel plates and 1.75 mm gap was also used for comparison purposes. Black diagrams and Cole-Cole plots were then used to evaluate the experimental data. Complex modulus and phase angle master curves were generated, and the rheological parameters compared. Finally, the two spring, two parabolic elements, one dashpot (2S2P1D) model was selected to investigate the rheological properties of the binders. Results indicate that the proposed procedure is a simple and reliable experimental method and represents an alternative experimental option to measure and analyze the rheological properties of asphalt binders at low temperature.

A simple method using a dynamic shear rheometer is proposed for determining high-temperature key parameters of asphalt binders in place of the ring-and-ball softening point, currently used in Germany. The test was recently introduced in the German standards under the name Bitumen-Typisierungs-Schnell Verfahren (BTSV), which translates to Binder-Fast-Characterization-Test. Two key parameters are obtained as the result of the test: the temperature TBTSV, at which the shear modulus is equal to 15.0 kPa, and the corresponding phase angle δBTSV. While TBTSV provides information on material hardness, δBTSV indicates the degree of modification. Based on these two parameters, a classification system is proposed for different asphalt binder grades commonly used in Europe. Additionally, the procedure was applied for rejuvenating aged asphalt binder extracted from reclaimed asphalt pavement (RAP). A linear relation is observed for the two key parameters when blending RAP binder with different proportions of rejuvenator. These findings were used to evaluate the effectiveness of different rejuvenating additives.

Hot mix asphalt (HMA) slabs produced by roller compaction can be used to core and cut specimens for further testing. The relation between the direction of compaction and testing in the laboratory is not always the same relation as it is between the direction of compaction and actual loading in the field. This paper presents outcomes of a study analysing the influence of the compaction direction on performance characteristics of roller-compacted HMA specimens. Performance parameters of a base layer mix are obtained from performance-based test methods, including high-temperature, stiffness, fatigue and low-temperature tests. The relation between direction of compaction and specimen testing is varied in all three dimensions to find relevant influences. From the results, it can be concluded that all obtained performance parameters are sensitive to the anisotropy of the material due to compaction, especially for stiffness and fatigue performance. For the high-temperature performance, specimens from path-and force-controlled compaction were compared. The applied compaction work rather than the compaction method is linked to the difference in the corresponding results. The uniformity of the compaction in terms of the variation of bulk density of the specimens reflects on the scattering of test results.

The Multiple Stress Creep and Recovery Test (MSCRT) is a testing method using the dynamic shear rheometer (DSR) to determine viscoelastic and viscous binder properties in order to assess the influence on the asphalt deformation behavior. The applicability of the test conditions and the corresponding simplified evaluation method formulated in the standards are reviewed in this paper. Here, rheological analyses are performed of the creep recovery curves corresponding to the Burgers model. The results of MSCRT prove that the viscous behavior of the binder is sufficiently described under the defined test conditions. However, the viscoelastic behavior may be determined more precisely at equi-viscose temperature. Further on the modification of the test enables to assess the effectiveness of the polymers contained in the bitumen on the one hand or the polymer content on the other.