# Experimental Investigation into Permeable Asphalt Pavement Based on Small-Scale Accelerated Testing
## 2 Materials and Methods
### Preparation of Structures  
In the first phase of this study, an experimental small-scale model pavement was built for MMLS3 testing. Figure 4 presents an overall view of building these structures. The building procedures are as follows:  
1. Subgrade: The waterproof geotextile was spread all over the bottom and all around the steel tank, soil evenly sprinkled on the inside of the steel tank, and a small roller used to compact it to the required thickness and compaction;  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sieve (mm)** & \multicolumn{4}{c}{**Percent Passing (\%)**} \\ \cline{2-5}  & \multicolumn{2}{c}{**CTB**} & **CTPB** & **PA** \\ \hline
31.5 & 100.0 & 100.0 & 100.0 \\
26.5 & - & 100.0 & 100.0 \\
19 & 75.5 & 92.0 & 100.0 \\
16 & - & - & 100.0 \\
13.2 & - & - & 90.0 \\
9.5 & 48.6 & 27.0 & 79.6 \\
4.75 & 29.0 & 13.0 & 29.2 \\
2.36 & 20.3 & 7.0 & 16.0 \\
1.18 & - & 5.0 & 12.3 \\
0.6 & 8.9 & - & 7.7 \\
0.3 & - & 2.0 & 4.6 \\
0.15 & - & - & 3.6 \\
0.075 & 3.5 & 1.0 & 5.4 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Gradations of surface and base materials.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Types** & **Surface Layer** & **Base Layer** & **Subgrade** & **Abbreviation** \\ \hline
4 PA-CTPB & PA & Cement-treated permeable base (CTPB) & Dry & 4 PA-CTPB-D \\
7 PA-CTPB & PA & Cement-treated permeable base (CTPB) & Dry & 7 PA-CTPB-D \\  & PA & Cement-treated base (CTB) & Wet & 7 PA-CTPB-W \\
7 PA-CTB & PA & Cement-treated base (CTB) & Dry & 7 PA-CTB-D \\ \hline \hline \end{tabular}
\end{table}
Table 2: Different types of structures and materials.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Types** & **Surface Layer** & **Base Layer** & **Subgrade** & **Abbreviation** \\ \hline
4 PA-CTPB & PA & Cement-treated permeable base (CTPB) & Dry & 4 PA-CTPB-D \\  & PA & Cement-treated permeable base (CTPB) & Wet & 4 PA-CTPB-W \\
7 PA-CTPB & PA & Cement-treated permeable base (CTPB) & Dry & 7 PA-CTPB-D \\
7 PA-CTB & PA & Cement-treated base (CTB) & Dry & 7 PA-CTB-W \\ \hline \hline \end{tabular}
\end{table}
Table 2: Different types of structures and materials.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameters** & \(\delta\) & \(\alpha\) & \(\beta\) & \(\gamma\) & **C1** & **C2** \\ \hline Fitting value & \(-2.671\) & \(7.062\) & \(-1.719\) & \(-0.342\) & \(15.600\) & \(147.564\) \\ \hline \hline \end{tabular}
\end{table}
Table 5: Model parameters of master curve.  
2. Base: The filtration geotextile was laid on top of the subgrade of 4 PA-CTPB and 7 PA-CTPB, and the waterproof geotextile was used to separate 4 PA-CTPB, 7 PA-CTPB, and 7 PA-CTB. Then the base materials were evenly paved and rolled to the required thickness; 3. Interface bonding layer: After 7 days, a layer of tack coat was evenly spread on top of the base, and the permeability of base was examined; 4. Surface layer: After 2 days, the porous asphalt mixture was paved and rolled to the required thickness with a small roller; the paving temperature was 175 \({}^{\circ}\)C, and the rolling temperature was 150 \({}^{\circ}\)C.  
These structures were instrumented with horizontal fiber Bragg grating strain gauges and temperature gauges as shown in Figure 5. These strain gauges were used to monitor transverse and longitudinal strain at the bottom of the surface layer. They were embedded 4 cm, 7 cm, and 7 cm below the surface of 4 PA-CTPB, 7 PA-CTPB, and 7 PA-CTB, respectively, in the interlayers of the asphalt concrete courses. They were positioned following a line coincident with the axis of the wheel track. Each strain gauge was alternatively set perpendicular or longitudinal to the wheel track.