## 1 Introduction
### Methods  
#### 2.2.1 Sizeable Wet Temperature Cycle Test  
Since the existing indoor test device is not able to simulate the sizeable wet temperature cycle environment suffered by asphalt pavement, a sizeable wet temperature cycle environment simulation device was developed in this paper, whose schematic diagram is shown in Figure 2. As can be seen from the figure, the developed device mainly consists of a central control system, rainfall system, temperature control system and blower system. Its operation principle is to set test parameters (the number of sizeable wet temperature cycles, the temperature of the specimen, rainfall amount, rainfall duration, blower length, etc.) through the central control system. The temperature of the specimen is controlled by the temperature control system to reach a certain value after the system is closed. The rainfall system begins with rainfall cooling and then automatically shuts down until the rainfall reaches the set time. The air blower system is initiated to dry the specimen until the air blower time runs out, and at this time, the air blower system will be closed. The environment for sizeable wet and temperature cycles can be simulated indoors by the circulation of a heater, rainfall, and air blower.  
Based on the measured road surface temperature and rainfall in Changsha during the hot and rainy months from 5 June to 5 August 2022 (June to September), the sizeable temperature cycle test parameters were determined in this paper. Eventually, the sizeable wet temperature cycle indoor simulation test was carried out under the condition that the rainfall amount was 31.4 mm/h (heavy rain), the rainfall duration was 30 min, the pavement temperature was 59.2 \({}^{\circ}\)C with a depth of 2 cm and the blower duration was 15 min. A double  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Grading Number**} & \multicolumn{8}{c}{**Passing Rate/\%**} & \multicolumn{8}{c}{**Oil-Rock**} & \multicolumn{1}{c}{**Void**} \\ \cline{2-13}  & **16** & **13.2** & **9.5** & **4.75** & **2.36** & **1.18** & **0.6** & **0.3** & **0.15** & **0.075** & **Ratio/\%** & **Ratio/\%** \\ \hline Lower limit of & & & & & & & & & & & & \\ grading & 100 & 90 & 68 & 38 & 24 & 15 & 10 & 7 & 5 & 4 & / & / \\
1\# & 100 & 90.5 & 69 & 39 & 25 & 16 & 11 & 7.5 & 5.2 & 4.1 & 4.7 & 5.9 \\
2\# & 100 & 93.5 & 74 & 49 & 33 & 24 & 16 & 12 & 8 & 5.5 & 4.8 & 5.0 \\
3\# & 100 & 99 & 84 & 67 & 49 & 37 & 27 & 19 & 14 & 7.8 & 5.1 & 4.1 \\ Higher limit of & 100 & 100 & 85 & 68 & 50 & 38 & 28 & 20 & 15 & 8 & / & / \\ grading & & & & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: AC-13 asphalt mixture designs.  
Figure 2: Schematic diagram of sizeable wet temperature cycle device. (**a**) Schematic diagram of the device. (**b**) Actual diagram of the device.  
layer rutting specimen served as the testing object, whose inner temperature was monitored by drilling holes and inserting temperature sensors. The drilling position was located 2 cm at the upper corner of the surface of the specimen. The single sizeable wet thermal test process is described as follows:1 Place the specimen and close the environmental box door.2 Turn on the heating system and stop heating when the temperature sensor reaches its set temperature.3 Turn on the rainfall system and then turn it off after rainfall is simulated for 30 min.4 Turn on the blower system, and turn it off after blowing for 15 min. The above steps were repeated for the sizeable wet temperature cycle test.