## 3 Experimental Design of Composite-Modified Asphal
### Determination of Compound Modifier Dosing
#### 3.3.3. Rheological Properties of Modified Asphalt  
In this paper, a DSR was used to perform temperature scans, frequency scans, and MSCR (multi-stress creep recovery) tests on the composite-modified asphalt. This was performed to determine the rheological properties of rubber powder and rock asphalt in the asphalt system. The temperature susceptibility of asphalt binders directly affects the service life of asphalt pavements, which are subjected to a combination of temperature and load during service. Their rutting resistance and riding comfort are closely related to their high-temperature rheological properties. This test conducts a temperature scan on original and short-term aged samples of composite-modified asphalt over a continuous range of temperatures. The specific test conditions are detailed in Table 10.  
The complex modulus G* indicates the shear deformation resistance of asphalt, with larger values indicating better stability at high temperatures. The phase angle \(\delta\) reflects the viscous behavior of asphalt and indicates the time delay between stress application and generation. A perfectly elastic material following Hooke's law exhibits no strain hysteresis, resulting in a phase angle \(\delta\) of zero. Smaller values of \(\delta\) at high temperatures indicate greater elasticity. Figures 3 and 4 present the temperature scan results for the original and short-term aged modified asphalt, respectively. From Figures 3 and 4, it can be observed that the G* value of both original and short-term aged samples gradually decreases with increasing temperature. This phenomenon is attributed to a decrease in elastic modulus and an increase in the viscous modulus of the asphalt material with increasing temperature. Compared to rubber powder-modified asphalt, composite-modified asphalt exhibits a higher G* value. The G* is further enhanced by the addition of a certain amount of Qingchuan rock asphalt. Therefore, incorporating rock asphalt at high temperatures can effectively improve the deformation resistance of rubber powder-modified asphalt. Additionally, mastic powder-modified asphalt exhibits a larger \(\delta\) and maintains a higher viscosity compared to other composite-modified asphalts. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Temperature Range** & **Temperature Gradient** & **Loading Strain** & **Angular Frequency** & **Parallel Plate** & **Sample Thickness** \\ \hline
58–106 \({}^{\circ}\)C & 6 \({}^{\circ}\)C & 12\% & 10 rad/s & 25 mm & 1 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 10: The Parameters of Temperature Scan Test. Figure 3: The G* and \(\delta\) of original samples. As temperature increases, the viscous portion also increases. The addition of rock asphalt tends to decrease the \(\delta\) of the composite-modified asphalt, indicating that rock asphalt can enhance its elastic proportion. Short-term aged samples exhibit higher G* values and lower \(\delta\) values compared to those of the original samples. This indicates that the aging process increases the elastic component of the asphalt and decreases its viscous component, leading to increased brittleness. However, an increase in rock asphalt diminishes changes in G* and \(\delta\), indicating that rock asphalt can enhance the aging resistance of asphalt. The rutting factor (G*/sin\(\delta\)) is derived from G* and \(\delta\) to further characterize the viscoelasticity of asphalt. A higher rutting factor indicates greater deformation resistance, suggesting superior performance at high temperatures for bonding materials. Tables 11 and 12 present corresponding rutting factor values for original and short-term aged samples. Figure 5 compares the rutting factors of original and short-term aged samples. The samples exhibit significant differences in rutting factor at lower temperatures, with a notable increase in G*/sin\(\delta\) observed when rock asphalt is added up to 6%. However, there is minimal variation in rutting factors among different types of asphalt at higher temperatures.