## 5 Conclusions  
High-modulus asphalt and its mixes have become crucial engineering materials for addressing heavy traffic issues in China. However, their limited low-temperature performance restricts their widespread use during the cold winter season in northern regions. Therefore, this study aims to obtain high-modulus composite-modified asphalt and mixture by adding rock asphalt to improve the modulus and rubber powder to improve low-temperature \begin{table}
\begin{tabular}{c c c} \hline \hline
**Asphal Mixture** & **Strain Level (\(\upmu\epsilon\))** & **Fatigue Life (Times)** \\ \hline \multirow{3}{*}{20C-20} & 400 & 567,860 \\ \cline{2-3}  & 500 & 72,400 \\ \cline{2-3}  & 600 & 35,310 \\ \hline \multirow{3}{*}{6R20C-20} & 400 & 555,890 \\ \cline{2-3}  & 500 & 74,320 \\ \cline{1-1} \cline{2-3}  & 600 & 34,730 \\ \hline \hline \end{tabular}
\end{table} 
Table 26: Fatigue test results. Figure 16: Results of water stability tests. performance. The basic properties of asphalt were evaluated through indoor tests using various masses of rubber powder and rock asphalt. Dynamic mechanical analysis of asphalt was employed to investigate the viscoelastic properties and determine the optimal dosage ratio for rubber powder and rock asphalt. Meanwhile, theoretical analysis was used to investigate the co-modification mechanism of asphalt between rubber powder and rock asphalt. Furthermore, the high-low-temperature properties, fatigue resistance, and mechanical properties of the high-modulus composite-modified asphalt mixture were evaluated. In summary, the following main conclusions were obtained:  
1. Among the five different origins of rock asphalt, Qingchuan rock asphalt was preferred for this study due to its higher asphalt content, lower ash content, and more detailed particle size distribution. This enables a better modification effect when in full contact with the basic asphalt. 2. The addition of rock asphalt and rubber powder can increase both the softening point and viscosity of basic asphalt while decreasing needle penetration. Although this makes it more viscous, they are capable of enhancing shear resistance and high-temperature performance. Additionally, using rock asphalt can enhance aging resistance but negatively impact low-temperature performance for high-modulus asphalts. However, the weakening effect can be mitigated by adding an appropriate amount of rubber powder. After a comprehensive analysis of the performance characteristics of high-modulus asphalt, it was determined that 20% mastic powder is optimal. 3. The amount of rubber powder is fixed, and the viscoelastic properties of composite-modified asphalt with different masses of rock asphalt are tested. The composite-modified asphalt exhibits superior elastic restoring force, and the effect becomes more pronounced as the mass of rock asphalt increases while its sensitivity to stress gradually decreases. After adding rock asphalt and mastic powder, the composite-modified asphalt showed improvements in both its instantaneous elastic component and delayed elastic part, resulting in enhanced rutting resistance factor and high-temperature performance. Considering all factors, suitable content would be 6%. 4. Compared to the rubber power-modified asphalt mixture, the high-modulus composite-modified asphalt mixture exhibits more significant improvements in resistance to deformation and water damage resistance at high temperatures. Although its low-temperature performance is slightly inferior to the former, the improved effect of rubber powder on low-temperature performance still provides some ductility for the high-modulus composite-modified asphalt mixture. In terms of fatigue life, the two materials exhibit comparable performance. Notably, high-modulus composite-modified asphalt is highly effective in enhancing mix modulus, and 20 \({}^{\circ}\)C asphalt mixes completely meet or exceed high-modulus standards. Conceptualization, L.W. ; Methodology, L.W. ; Software, L.W. ; Validation, L.S. and Q.L. ; Formal analysis, L.S. ; Investigation, L.W.