## 3 Results and Discussion
### Ot  
(a) The gradation of the asphalt mixture affected both the \(R\) and \(CRI\) (as shown in Figure 22). A good linear correlation between these two parameters was observed, with  
Figure 21: Binarization of SCB specimens. (**a**) 10A-1. (**b**) 10B-1. (**c**) 10C-1. (**d**) 10C-2. (**e**) 10C-MZ. (**f**) 10C-GG. (**g**) 10C-3. Figure 20: Load–displacement curve. R\({}^{2}\) = 0.8906 and \(p\)-value \(<\) 0.01 (as shown in Figure 23). These results suggest that the \(R\) and \(CRI\) of the asphalt mixture vary in the same way with the gradation changes. Therefore, \(R\) and \(CRI\) were recommended as evaluation indicators. (b) The gradation of the asphalt mixture had an effect on the \(R\) and \(CRI\). The \(R\) and \(CRI\) indicated the resistance of the asphalt mixture to damage under loading. As shown in Figure 22, the gradation range of 10A had the highest \(R\) and \(CRI\), indicating the worst performance in terms of damage resistance. The gradation ranges of 10B and 10C had lower \(R\) and \(CRI\), indicating better performance in terms of damage resistance. Among them, the gradation of 10A-1 had the highest \(R\) with a value of 14.59%, while the 10C-MZ gradation had the lowest value. The \(CRI\) had the lowest value for the gradation of 10A-1 and the highest value for the gradation of 10B-1 with a difference of 18.1%. Therefore, it can be concluded that the gradation range of 10A had unsatisfactory performance, while the gradation ranges of 10B and 10C had better performance. (c) Correlation analysis of the gradation parameters with \(R\) and \(CRI\) showed that different gradation parameters affected the performance of the asphalt mixture to different degrees. As shown in Figure 24, the \(CA\) had the highest correlation coefficients with \(R\) and \(CRI\), with values greater than 0.6. This indicated that \(CA\) was an important factor affecting the performance of the asphalt mixture. Therefore, \(CA\) was selected as the main parameter of gradation change to further explore its influence on the performance of the asphalt mixture. Figure 23: Correlation between \(R\) and \(CRI\). Figure 22: OT results of AR-SAMI. (d) The \(R\) of the asphalt mixture increased and the \(CRI\) decreased as the \(CA\) increased (as shown in Figure 25). When the \(CA\) increased, the content of 2.36 mm aggregate particles in the coarse aggregate fraction increased, which reduced the interlocking and stability of the coarse aggregate skeleton and disrupted the dense structure of the asphalt mixture. As a result, the cracks encountered less resistance and propagated faster during the OT, leading to lower performance and higher damage to the asphalt mixture. The performance of the asphalt mixture was affected by the gradation, but the gradation range alone was not sufficient to determine the quality of the asphalt mixture. The results of different tests showed that different gradation ranges had different advantages and disadvantages in terms of flexural fatigue resistance, low-temperature cracking resistance, resistance to crack expansion, and deformation resistance. Therefore, to better characterize the performance of the asphalt mixture, the influencing factors and the optimal values of the gradation parameters need to be further analyzed, as shown in Table 6. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Gradation** & \(P_{\textbf{2.75 nm}}\) & \(P_{\textbf{2.36 nm}}\) & \(PCSI\) & \(D_{c}\) & \(CA\) &
\begin{tabular}{c} **Asphalt** \\ **Film** \\ **Thickness** \\ \end{tabular} \\ \hline BBT & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) & & \\ LT-SCB test & & & & & & \\ CE-SCB test & \(\surd\) & \(\surd\) & \(\surd\) & & & \\ OT & & & & & \(\surd\) & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Main gradation parameters of different test. Figure 24: R\({}^{2}\) of gradation parameters fitting curve. (**a**) \(R\). (**b**) \(CRI\). Figure 25: Correlation of \(CA\) with \(R\) and \(CRI\). The main influencing parameters of the asphalt mixture performance varied depending on the test method.