# Research on Performance of a Dense Graded Ultra-Thin Wearing Course Mixture
## 3 Result and Discussions
### Texture Depth Evaluation  
According to the previous test plan, all of the designed asphalt mixtures including M-UWM10, UWM10, SMA10, SMA13, and AC13 were submitted to the combination of the texture depth test and the wheel tracking test. The measured texture depth for different asphalt mixtures before and after the wheel tracking test are shown in Figure 6a, and the loss ratios defined as the texture depth after the wheel tracking test compared to the texture depth before the wheel tracking test are shown in Figure 6b. The rutting depth, for all of the five asphalt mixtures after the wheel tracking test are also shown in Figure 6b, and the correlation between the reduced ratio of texture depth and the rutting depth after the wheel tracking test is shown in Figure 6c. As shown in Figure 7, field texture depth tests were also conducted for the two test roads. Table 4 shows the field measured values of the original texture depth and the texture depth after one year of traffic loading for the two test roads with the M-UWM10 wearing course and the SMA10 wearing course, respectively.  
Figure 5: Test results for road performance evaluation: (**a**) dynamic stability; (**b**) failure strain; (**c**) Marshall stability ratio; (**d**) tensile strength ratio.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Performance** & **Dynamic Stability** & **Failure Strain** & **Marshall Stability** & **Tensile Strength** \\
**Index** & **(cycles/mm)** & **(\(\mu\epsilon\))** & **Ratio (\%)** & **Ratio (\%)** \\ \hline Requirements & \(\geq\)3000 & \(\geq\)2500 & \(\geq\)85 & \(\geq\)80 \\ Test method & T0719-2011 & T0715-2011 & T0709-2011 & T0729-2000 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Pavement performance verification for the M-UWM10 mixture Figure 6: Test results from the combination of the texture depth test and the wheel tracking test: (**a**) texture depth before and after wheel tracking test; (**b**) loss ratio of texture depth after wheel loading; (**c**) correlation between the reduced ratio of texture depth and the rutting depth after the wheel tracking test.  
From Figure 6a, it can be seen that the SMA mixtures have higher texture depth than the other three asphalt mixtures, which have similar texture depth. It is mainly because the SMA mixtures use gap gradation while the other three asphalt mixtures use dense gradation. From the data after the wheel tracking test shown in Figure 6a, it can be seen that, due to its original high texture depth, SMA13 still have the highest texture depth, the M-UWM10 and SMA10 have similar texture depth, and the UWM10 and AC13 show a similar texture depth, which are the lowest. From Figure 6b, it can be further seen that the UWM10 has the biggest reduced ratio of texture depth, SMA10 and AC13 show a similar reduced ratio, which are lower than that of UMW10, while M-UWM10 and SMA13 have a similar reduced ratio, which are lower than the other three mixtures. Furthermore, the M-UWM10 shows a lower reduced ratio than SMA13.  
From Figure 6c, it could be observed that the reduced ratio of texture depth increases with the growing of rutting depth. It indicates that the degradation behaviour of texture depth has a good correlation with the rutting resistance of asphalt mixture, and higher rutting resistance leads to less degradation of texture depth during the wheel tracking test.  
The field test results confirm well with the laboratory test analysis. From Table 4, it can be seen that, although the SMA10 has a bigger texture depth than the M-UWM10 before traffic loading, after one year of traffic loading, the SMA10 shows a higher reduced ratio of texture depth than the M-UWM10, and the texture depth of the two mixtures becomes similar to each other.  
Thus, the M- UWM10 has similar skidding resistance with other dense graded asphalt mixtures such as AC13 but better wearing resistance than other asphalt mixtures including both the dense graded asphalt mixture and the gap graded asphalt mixture.