## 3 Results and Discussion
### Comparative Analysis of Three Kinds of Fatigue Tests  
In order to analyze the comprehensive evaluation results of different asphalt mixtures in the three fatigue tests, the fatigue tests at or nearby \(300\times 10^{-6}\) strain were unified and chosen to compare the fatigue life of different asphalt mixtures under the three different tests. According to the order of fatigue life of different mixtures, the mixture with the best fatigue performance scores 6 points and the worst scores 1 point. The total scores of the three test methods for various asphalt mixtures are given by analogy. The results are shown in Table 5.  
1. In the 4 PB fatigue test, WPES has the best fatigue life, which is 19.03 times of the fatigue life of the base asphalt mixture. In the Trapezoidal Beam fatigue test, SBS6 has the best fatigue life, which is 127.48 times of the fatigue life of the base asphalt mixture. In the OT fatigue test, SBS6 has the best fatigue life, which is 3.1 times of the fatigue life of base asphalt mixture.  
2. According to the total score, the fatigue performance of the asphalt mixture is ranked: SBS6 \(>\) 4S4P \(>\) WPES \(\approx\) SBS4 \(>\) WA \(>\) SK70.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Asphalt** & **SK70** & **WA** & **SBS4** & **4S4P** & **WPES** & **SBS6** \\ \hline \multirow{3}{*}{4 PB} & Fatigue life & 118,340 & 85,870 & 1,123,940 & 2,055,560 & 2,265,690 & 2,081,300 \\  & Ratio of fatigue life to SK70 mixture & 1 & 0.73 & 9.5 & 17.37 & 19.15 & 17.59 \\  & Score & 2 & 1 & 3 & 4 & 6 & 5 \\ \hline \multirow{3}{*}{Trapezoidal Beam} & Fatigue life & 10,441 & 14,779 & 890,451 & 561,510 & 412,352 & 1,331,028 \\  & Ratio of fatigue life to SK70 mixture & 1 & 1.42 & 85.28 & 53.78 & 39.49 & 127.48 \\  & Score & 1 & 2 & 5 & 4 & 3 & 6 \\ \hline \multirow{3}{*}{OT} & Fatigue life & 322 & 343 & 594 & 612 & 384 & 997 \\  & Ratio of fatigue life to SK70 mixture & 1 & 1.07 & 1.84 & 1.9 & 1.19 & 3.1 \\  & Score & 1 & 2 & 4 & 5 & 3 & 6 \\ \hline \multirow{3}{*}{Trapezoidal Beam} & Total score & 3 & 5 & 12 & 13 & 12 & 17 \\ \hline \hline \end{tabular}
\end{table}
Table 5: The fatigue life and score of different asphalt mixtures in different fatigue tests.  
3. In the three fatigue tests, the fatigue lives of SK70 and WA are significantly lower than that of the other four asphalt mixtures, which is also identical to the experience in practical engineering [22; 23; 24], that is, the fatigue life of the base asphalt mixtures is not significantly improved by a warm mixing agent [25; 26]. The fatigue performance of the asphalt mixture is improved by adding SBS, and the fatigue performance of the asphalt mixture is improved more obviously with the increase of SBS content. The addition of WPE and PA610 also improves the fatigue performance of the asphalt mixture in varying degrees. Considering fatigue performance and cost saving, these two new modification methods can replace part of the SBS-modified asphalt.  
4. In the three fatigue tests, the fatigue performance of the mixture can be roughly distinguished, but the specific rankings are different. The test samples, waveforms, and frequencies are different, so the evaluation results of fatigue life values cannot be directly transformed. However, in the research and development of new materials, the three different fatigue tests can be used simultaneously to obtain a more comprehensive and objective evaluation.