# Evaluation of Anti-Skid Performance of Asphalt Mixture Based on Accelerated Loading Test
## 3 Result and Discussion  
### Texture Depth Test  
The pavement texture depth, denoted as MTD, measures the macrotexture characteristics of road surfaces. Its magnitude positively correlates with the roughness of the road surface, which, in turn, aids in enhancing the drainage and safety of the pavement. Table 4 presents the MTD values before and after the application of 600,000 loading cycles, while Figure 5 illustrates the trend of MTD decay with increasing loading cycles. As depicted in Figures 4(a) and 4(a) and Table 4, it is widely acknowledged that the structural depth of compacted asphalt mixtures tends to increase with the greater content of coarse aggregate, a larger nominal maximum particle size, and a lower oil-stone ratio. The oil-stone ratios of S1, S2, and S3 are recorded at 4.4%, 4.9%, and 5.4%, respectively, thus resulting in the diminishing trend of macroscopic texture depth from S1 to S3. Additionally, S4's 4.75 mm sieve pass rate increased from 32% to 40%, and the 9.5 mm sieve pass rate increased from 57.5% to 65.6%, along with the gradation becoming finer as compared to S2. Therefore, the initial MTD value of S4 is smaller than that of S2. Further, S5 and S6  
Figure 5: The relationship between MTD and accelerated loading times. are composed of andesites, while limestone has the same gradation. Consequently, the andesite asphalt mixture exhibits the highest initial MTD value compared to S2. The MTD values of the six AC-16 anti-skid surface layers exhibit a decreasing trend as the loading times increase. Specifically, a faster MTD decay rate is observed before loading 50,000 times, followed by a slowdown in the attenuation rate between 50,000 and 100,000 loading cycles. After 100,000 loading cycles, the MTD values of all programs remain stable. This phenomenon is mainly attributed to the slight compaction of the AC-16 asphalt mixture at the beginning of loading, leading to rapid MTD decay. However, as the loaded tire rubs against the asphalt mixture, the road surface particles become more compact, mitigating the impact of peaks and bumps on the road surface. The wheels' wear and tear also stabilizes road surface particles, resulting in a slower MTD decay rate. Upon subjecting the six AC-16 anti-skid surface layers to 600,000 cycles of accelerated loading, the fine-graded S4 displayed the highest attenuation rate of MTD, followed by S6 (limestone aggregate). In contrast, S5 (andesite aggregate) exhibited the lowest MTD attenuation rate. This trend can be attributed to the relatively thin gradation used by S4, resulting in compaction deformation, rearrangement of road surface aggregates, and a substantial attenuation of MTD. The MTD value of S4 after 600,000 loading cycles was also the smallest among all programs. In contrast, S6 (limestone aggregate) displayed a relatively smooth aggregate surface, as evidenced by Figure 7c, and weak compaction ability between aggregates. This low compaction ability was linked to a low polishing value, a high abrasion value, and poor wear resistance. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Plan Number** & **MTD Initial Value/mm** & **MTD Final Value/mm** & **Attenuation Amplitude/mm** & **Attenuation Rate \%** & **Mean Decay Rate/\%** \\ \hline S1 & 1.13 & 0.90 & 0.23 & 20.60 & \\ \hline S2 & 1.02 & 0.80 & 0.23 & 22.10 & \\ \hline S3 & 0.91 & 0.78 & 0.14 & 14.90 & \\ \hline S4 & 0.71 & 0.49 & 0.22 & 30.50 & \\ \hline S5 & 1.10 & 0.98 & 0.12 & 10.90 & \\ \hline S6 & 1.01 & 0.76 & 0.25 & 24.80 & \\ \hline S7 & 1.21 & 1.10 & 0.12 & 9.70 & \\ \hline S8 & 1.05 & 1.00 & 0.05 & 4.50 & \\ \hline S9 & 0.67 & 0.60 & 0.08 & 11.30 & \\ \hline S10 & 1.49 & 1.36 & 0.13 & 8.60 & \\ \hline S11 & 1.38 & 1.13 & 0.25 & 18.00 & \\ \hline S12 & 0.80 & 0.77 & 0.03 & 3.90 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Pavement structure depth and loading times. Figure 6: Surface changes of the asphalt mixture under different load repetitions.