## 5 Results and Discussion
### Low-Temperature Bend Test  
The beam bend test evaluates crack resistance at a low temperature based on flexural tensile strength, flexural tensile strain and bending stiffness modulus when the mixture is damaged. The material composition of the specimens used in this test are based on the results of Figures 4, 6 and 7. A low temperature bend test, as shown in Figure 11, was executed with reference to the test method of T 0715-2011 in Chinese specification JTG E20-2011 [32]. Table 19 and Figure 12 are the results of the low temperature bend test. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Mixture** & \begin{tabular}{c} **Marshall Stability** \\ **(MS)/kN** \\ \end{tabular} & \begin{tabular}{c} **Vacuum Saturated Marshall** \\ **Stability (MS\({}_{2}\))/kN** \\ \end{tabular} & \
\begin{tabular}{c} **Residual Marshall** \\ **Stability (MS\({}_{0}^{\prime}\))/\%** \\ \end{tabular} &
\begin{tabular}{c} **Requirement/\%** \\ \end{tabular} \\ \hline SMA-II-1 & 10.93 & 10.03 & 91.8 & \\ SMA-II-2 & 10.21 & 9.52 & 93.2 & \(\geq\)85 \\ SMA-II-3 & 11.02 & 9.96 & 90.4 & \\ \hline \hline \end{tabular}
\end{table} 
Table 16: Results of vacuum saturated Marshall stability test. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Mixture** & \begin{tabular}{c} **Original Splitting** \\ **Strength (\(R_{\text{T1}}\))/MPa** \\ \end{tabular} & \begin{tabular}{c} **Freeze-Thaw** \\ **Splitting Strength (\(R_{\text{T2}}\))/MPa** \\ \end{tabular} & \
\begin{tabular}{c} **Tensile Strength** \\ **Ratio (TSR)/\%** \\ \end{tabular} &
\begin{tabular}{c} **Requirement/\%** \\ \end{tabular} \\ \hline SMA-II-1 & 1.13 & 1.01 & 89.4 & \\ SMA-II-2 & 1.07 & 0.97 & 90.7 & \(\geq\)80 \\ SMA-II-3 & 1.17 & 1.04 & 88.9 & \\ \hline \hline \end{tabular}
\end{table} 
Table 17: Results of Freeze-thaw splitting test. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Mixture** & **Texture Depth (TD)/mm** & **BPN** \\ \hline SMA-II-1 & 1.02 & 76 \\ SMA-II-2 & 0.87 & 66 \\ SMA-II-3 & 0.96 & 73 \\ \hline \hline \end{tabular}
\end{table} 
Table 18: Test results of skid resistance performance. According to the results shown in Table 19, the flexural strength of the SBS-modified SMA-I mixture is the largest, while the maximum flexural strain is the smallest. The flexural strengths of all SMA-II mixtures are lower than those of SMA-I mixture, while, in contrast, the maximum flexural strains are much larger than those of SMA-I. The flexural strength of SMA-II-1, II-3 and II-2 respectively are 78.4%, 75.5% and 72.5% of that of SMA-I, the maximum flexural strains respectively are higher than that of SMA-I by 26.1%, 39.9% and 51.9%. The maximum flexural strain of SMA-I is 7438.7, while for all SMA-II mixtures, the test values are greater than 10,000--the flexural strain of SMA-II-2 is more than 15,000, which is far greater than the 3000 that is required by Chinese specification JTG F40-2004 [39]. The flexural stiffness modulus of all SMA-II mixtures is lower than that of the SMA-I mixture--the flexural stiffness modulus of II-2 is only 35% of that of SMA-I. All of these demonstrate the good low-temperature flexibility, deformation and crack resistance of SMA-II. Figure 13 shows that the failure load of the SMA-I mixture decreases rapidly after reaching the maximum, which indicates there is obvious brittle fracture. The load-strain curve of SMA-II is a flat parabolic curve without a brittle fracture point. Among the three load-strain curves, SMA-II-1 has the maximum failure load but the minimum strain interval. SMA-II-2 has the minimum failure load but the maximum strain interval, as well as the flattest load-strain curve, which is related to the high asphalt content 8.1% of SMA-II-2. The load-strain curve of SMA-II-3 is in between the load-strain curves of SMA-II-1 and SMA-II-2. To sum up, the low-temperature performance of the SMA-I (SBS-modified) mixture is much worse than that of the rubberized SMA-II mixtures, which indicates that the asphalt-rubber binder is the major factor that affects the low-temperature performance of the mixture.