## 3 Tests and Results  
### The Evaluation of the Thermal Stability and Aging Resistance for Modified Asphalt  
#### 3.1.1 Thermal Stability  
The dynamic shear rheometer (DSR) can be employed to measure the rheological properties of asphalt at high and medium temperatures to evaluate the thermal stability of asphalt. Within the viscoelastic range, it was implemented to detect the complex shear modulus \(G^{*}\), phase angle \(\delta\) \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Test Items** & **BRA** & **BRA + 3\% SBR** & **BRA + 5\% SBR** & \
\begin{tabular}{c} **BRA + 5\%** \\ **Nano-CaCO\({}_{3}\)** \\ \end{tabular} &
\begin{tabular}{c} **BRA + 10\%** \\ **Nano-CaCO\({}_{3}\)** \\ \end{tabular} \\ \hline Penetration (25 \({}^{\circ}\)C, 0.1 mm) & 26.3 & 24.0 & 22.4 & 24.2 & 22.7 \\ PI & 1.862 & 1.703 & 1.961 & 1.870 & 1.912 \\ T\({}_{1.2}\) (\({}^{\circ}\)C) & \(-\)18.8 & \(-\)16.6 & \(-\)17.1 & \(-\)17.7 & \(-\)17.0 \\ T\({}_{800}\) (\({}^{\circ}\)C) & 73.5 & 73.7 & 76.5 & 73.5 & 74.7 \\ Softening Point (\({}^{\circ}\)C) & 64.7 & 75.8 & 81.4 & 65.4 & 66.9 \\ Ductility (5 cm/min, 15 \({}^{\circ}\)C, cm) & 7.5 & 20.1 & 26.7 & 8.4 & 12.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The basic technical properties of modified asphalts. and anti-rutting factor \(G^{*}/\sin\!\delta\) of asphalt, and its rheological properties can be evaluated. The test temperature of a dynamic shear rheometer (DSR) starts from 58 \({}^{\circ}\)C. If the anti-rutting factor \(G^{*}/\sin\!\delta\) is qualified, the test was performed at 64 \({}^{\circ}\)C for one grade, and the requalification continues to increase to 70 \({}^{\circ}\)C for testing until a test temperature of \(G^{*}/\sin\!\delta<\) 1.0 KPa then stopped the test. The complex shear modulus \(G^{*}\) indicates the ability of the material to resist the shear deformation. The greater the value of \(G^{*}\), the harder the asphalt, which meant a better rutting resistance. The smaller the phase angle was, the more elastic the components in the asphalt. The dynamic shear rheometer (DSR) test was implemented to qualify the high temperature performance of nano-CaCO\({}_{3}\)/BRA and SBR/BRA compound-modified asphalt. The results of dynamic shear rheometer (DSR) tests before the aging of nano-CaCO\({}_{3}\)/BRA and SBR/BRA compound-modified asphalts with different contents are shown in Figures 2-4, respectively. Figure 2 shows that the complex shear moduli \(G^{*}\) of the five modified asphalts decreasing with increasing temperature. Under the same temperature conditions, the complex shear modulus \(G^{*}\) of 10% nano-CaCO\({}_{3}\)/BRA compound-modified asphalt is the largest. The BRA has the smallest complex shear modulus \(G^{*}\). The complex shear modulus of 5% SBR/BRA compound-modified asphalt is much larger than that of 3% SBR/BRA compound-modified asphalt. This shows that the addition of nano-CaCO\({}_{3}\) and SBR can significantly improve the resistance of BRA to deformation, and with the increase of the amount of addition, the deformation resistance is enhanced. Figure 2: The relationship between complex shear modulus \(G^{*}\) and the temperature of nano-CaCO\({}_{3}\)/BRA and SBR/BRA compound-modified asphalt. As can be observed from Figure 3, under the same temperature conditions, the phase angle \(\delta\) of the 5% SBR/BRA compound-modified asphalt is the smallest, and that of the BRA is the largest. This shows that the addition of nano-CaCO\({}_{3}\) and SBR can improve the elastic composition of the BRA, and the 5% SBR/BRA compound-modified asphalt is the most likely to restore deformation compared with the other four kinds of modified asphalt. It can be observed from Figure 4 that at the same temperature, the anti-rutting factors \(G^{\star}\)/sin\(\delta\) of the four kinds of BRA compound-modified asphalt are larger than that of BRA at the same temperature, and the rutting resistance of 10% nano-CaCO\({}_{3}\)/BRA compound-modified asphalt is the best.