## 4 Discussion
### Correlation Analysis of SRNR Performance  
Based on the analysis of orthogonal test results, it is not difficult to find that there is a certain correlation between the surface texture characteristics of EAC and its SRNR performance. Therefore, a correlation analysis was conducted on the orthogonal test data of nine groups of 27 EAC slab specimens, including exposed aggregate depth, exposed aggregate area ratio, pendulum value, and noise value. The analysis results are shown in Figures 12 and 13, respectively. The results showed that the coefficient of determination \(R^{2}\) between noise value and exposed aggregate depth, as well as between pendulum value and exposed aggregate area ratio, both exceeded 0.64, indicating that both relationships exhibited high correlations. As can be seen from Figure 12, as the exposed aggregate depth increases, the noise value gradually decreases and stabilizes. Based on this variation characteristic of noise value, an inverse exponential function was used for fitting, and the coefficient of determination \(R^{2}\) was found to be 0.69, indicating an inverse exponential function relationship between noise value and exposed aggregate depth. This relationship between noise value and exposed aggregate depth also reflects the variation pattern of the air pumping effect \begin{table}
\begin{tabular}{c c c c} \hline
**Test Indicators** & \begin{tabular}{c} **Technical** \\ **Requirements** \\ \end{tabular} & **EAC** & \begin{tabular}{c} **Grooved** \\ **Concrete** \\ \end{tabular} \\ \hline \begin{tabular}{c} Exposed aggregate depth/mm \\ Exposed aggregate area ratio/\% \\ Pendulum value/BPN \\ \end{tabular} & 65–75 & 68.75 & / \\ \begin{tabular}{c} Noise value/dB \\ \end{tabular} & / & 77.56 & 58.98 \\ \begin{tabular}{c} 28-day compressive strength/MPa \\ \end{tabular} & \(\geq\)40 & 47.81 & 43.23 \\ \
\begin{tabular}{c} 28-day flexural strength/MPa \\ \end{tabular} & \(\geq\)5 & 5.35 & 5.12 \\
\begin{tabular}{c} Slump/mm \\ \end{tabular} & 10–30 & 14 & 23 \\ \hline \end{tabular}
\end{table} 
Table 6: The optimal mix proportions verification and comparison. Figure 11: Tire/surface noise spectrum of grooved concrete and EAC. generated by tires traveling at a certain speed on EAC pavement. Specifically, as the exposed aggregate depth increases, the voids between the tire and the EAC surface during contact increase, and the air discharge channels become more unobstructed, reducing the likelihood of forming air compression in enclosed voids. Consequently, the air pumping effect between the tire and the pavement weakens, and the surface noise value of the pavement gradually decreases. As can be seen from Figure 13, as the exposed aggregate area ratio increases, the pendulum value shows a trend of first decreasing, then increasing, and finally decreasing again, forming a cubic polynomial relationship with a coefficient of determination \(R^{2}\) reaching 0.78. This variation trend between the pendulum value and exposed aggregate area ratio mainly depends on the contact condition between the rubber slider of the pendulum friction tester and the surface texture of EAC during testing. Generally, the mortar texture contains a large number of rich micro-textures, and under the condition that the rubber slider simulates the low-speed driving of automobile tires, the micro-textures play a major role in pavement skid resistance. Therefore, when the exposed aggregate area ratio is less than 64%, the larger the exposed aggregate area ratio, the smaller the contact area between the rubber slider and the mortar texture, and the lower the skid resistance performance of the EAC surface. When the exposed aggregate area ratio is between 64% and 71%, the coarse aggregate texture becomes the main texture.