## 3 Materials and Testing Methods
### Testing Methods
#### 3.2.4 Rheological Tests  
1. Viscosity test In the mixing and compacting process of asphalt mixture, the viscosity of asphalt shall be kept within a certain range. Excessive viscosity will cause insufficient compacting of asphalt mixture, and too low viscosity will result in a waste of energy. The workability of asphalt can be characterized by a viscosity test. The viscosity of specimen is measured respectively at 120 \({}^{\circ}\)C, 135 \({}^{\circ}\)C, 150 \({}^{\circ}\)C, 165 \({}^{\circ}\)C, and 180 \({}^{\circ}\)C in this study. For the details of the test, refer to ASTM D4402 [19]. 2. Multiple Stress Creep Recovery (MSCR) test In the Standard Specification for Performance Classification of Asphalt binder (AASHTO:M320), rutting factor (\(\mathrm{\,I\,G^{*}\,|\,/sin\delta}\)) is adopted as the high-temperature performance indicator of asphalt. Rutting factor can predict the high temperature performance of unmodified asphalt well, but there is still a dispute on its applicability for modified asphalt [20; 21]. An MSCR test can reflect the nonlinear rheological response of modified asphalt under a large stress, and it has been confirmed that non-recoverable creep compliance (\(\mathrm{J_{nr}}\)) has a good correlativity with the rutting property of modified asphalt [22]. Both the physical and chemical properties change dramatically after asphalt aging, and W-oil rejuvenated asphalt is regarded as modified asphalt. To predict the high-temperature performance of W-oil rejuvenated asphalt more accurately, a \(\mathrm{J_{nr}}\) indicator achieved by the MSCR test is adopted in this paper. The MSCR test applies an AR 2000 dynamic shear rheometer (DSR): an 8-mm plate is applied for the specimens of 0%WRA and 5%WRA, and the gap between the parallel plates is set to be 2 mm; a 25 mm plate is applied for the specimens of Virgin, 10%WRA, 15%WRA and 20%WRA, and the gap between the rotor's parallel plates is set at 1 mm. The testing temperature for specimens is 60 \({}^{\circ}\)C, and the loading frequency is 10 rad/s. Specimens are loaded respectively under a stress of 0.1 kPa and 3.2 kPa; the loading process is to load for 1 s, then recover for 9 s. Each stress includes 10 cycles of loading and recovering. 3. Time Sweep (TS) test Superpave research proposes the fatigue factor (\(\mathrm{\,I\,G^{*}\,|\,\times\,sin\delta}\)), which is similar to the asphalt rutting factor and takes it as a control index of asphalt fatigue resistance. However, the fatigue factor cannot characterize the fatigue damage characteristics, and it has poor correlation with the asphalt mixture's fatigue property. Asphalt fatigue life, which is obtained from the time sweep test, can reflect the fatigue resistance of the corresponding asphalt mixture [23]. The number of loading cycles (\(\mathrm{N_{F90}}\)) in the case of a complex modulus decreased to 50% is taken as the index for judging the asphalt fatigue [16]. The time sweep test is carried out to characterize the fatigue property of virgin, aged, and rejuvenated asphalt. The TS test applies AR 2000 DSR, which is the same instrument as in the MSCR test. An 8-mm plate is applied for 0%WRA and 5%WRA, and the gap between the parallel plates is set at 2 mm; a 25-mm plate is applied for Virgin, 10%WRA, 15%WRA, and 20%WRA, and the gap between the parallel plates is set 1 mm. A 5% strain control mode is applied for all of the specimens, the loading frequency is 10 rad/s, and the testing temperature is 20 \({}^{\circ}\)C.
4. Bending Beam Rheometer (BBR) test The model of the testing instrument is TE-BBR. The flexural creep stiffness or flexural creep compliance, as determined from this test, describes the low-temperature stress-strain time response of the asphalt binder at the test temperature within the range of linear viscoelastic response. Creep stiffness (S) and creep rate (m) are used to assess the low temperature anti-cracking property in this paper.