## Materials and Methods
### Testing Methods  
The density of specimens was calculated by measuring the mass and volume with 100 \(\times\) 100 \(\times\) 100 mm\({}^{3}\) specimens. Before the measurement, all specimens were dried in an oven at 105 \({}^{\circ}\)C for 24 h.  
Porosity is an important index for PC. In general, there is open pore, semi-open pore, and closed pore. Only open pore and semi-open pore are effective for concrete permeability, but all three kinds influence the microstructure and macroproperties of PC. In this study, total porosity (open pore, semi-open pore, and closed pore) and effective porosity (open pore and semi-open pore) were measured with 100 \(\times\) 100 \(\times\) 100 mm\({}^{3}\) specimens in every group and calculated by the following equations:  
\[\mathrm{P_{t}}=(1-\frac{\mathrm{m_{1}-m_{0}}}{\mathrm{V\rho_{w}}})\times 100\% \tag{1}\]  
\[\mathrm{P_{e}}=(1-\frac{\mathrm{m_{2}-m_{0}}}{\mathrm{V\rho_{w}}})\times 100\% \tag{2}\]  
where \(\mathrm{P_{t}}\) is the total porosity of the specimen (%); \(\mathrm{P_{e}}\) is the effective porosity of the specimen (%); \(\mathrm{m_{0}}\) is the mass of the specimen submerged in water (g); \(\mathrm{m_{1}}\) is the mass of the oven-dried specimen (g); \(\mathrm{m_{2}}\) is the saturated surface-dry mass of the specimen (g); \(\mathrm{\rho_{w}}\) is the water density (g/cm\({}^{3}\)), and \(\mathrm{V}\) is the volume of the specimen (cm\({}^{3}\)). Generally, the constant head permeability test and falling head permeability test are used to measure the permeability coefficient of PC. In this study, the permeability coefficient was determined by the constant head permeability test according to the national standard [33]. In every group, 100 \(\times\) 100 \(\times\) 100 mm\({}^{3}\) specimens were used to measure the permeability coefficient. The test method for PC permeability coefficient is shown in Figure 1. In order to prevent leakage around the specimen, \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Aggregate Size (mm)**} & \multirow{2}{*}{**Water-Binder Ratio**} & \multirow{2}{*}{**Designed Porosity (\%)**} & \multirow{2}{*}{**Coarse Aggregate (kg/m\({}^{3}\))**} & \multirow{2}{*}{**Cement (kg/m\({}^{3}\))**} & \multirow{2}{*}{**Water (kg/m\({}^{3}\))**} & \multirow{2}{*}{**Superplasticizer (kg/m\({}^{3}\))**} \\  & & & & & & & \\ \hline
1 & 4.75–9.5 & 0.25 & 15 & 1381 & 590 & 147 & 5.90 \\
2 & 4.75–9.5 & 0.30 & 20 & 1381 & 465 & 140 & 4.65 \\
3 & 4.75–9.5 & 0.35 & 25 & 1381 & 359 & 126 & 3.59 \\
4 & 9.5–13.2 & 0.25 & 20 & 1430 & 475 & 119 & 4.75 \\
5 & 9.5–13.2 & 0.30 & 25 & 1430 & 359 & 108 & 3.59 \\
6 & 9.5–13.2 & 0.35 & 15 & 1430 & 478 & 167 & 4.78 \\
7 & 13.2–16 & 0.25 & 25 & 1470 & 358 & 90 & 3.58 \\
8 & 13.2–16 & 0.30 & 15 & 1470 & 487 & 146 & 4.87 \\
9 & 13.2–16 & 0.35 & 20 & 1470 & 379 & 133 & 3.79 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Mix ratio of pervious concrete (PC). the specimen was sealed with plasticine and plastic wrap. The permeability coefficient can be calculated by the following equation:  
\[\mathrm{k}=\frac{\mathrm{QL}}{\mathrm{AHt}} \tag{3}\]  
where k is the permeability coefficient (mm/s); Q is the discharged amount of water in t time (mm\({}^{3}\)); L is the height of the specimen (mm); A is the upper surface area of the specimen (mm\({}^{2}\)); H is the height of water head (mm), H = 150 mm; t is the time (s), t = 300 s.  
The compressive strength and flexural strength of PC specimens were measured according to the national standard [34]. The specimen for the compressive strength test was 100 \(\times\) 100 \(\times\) 100 mm\({}^{3}\). Three-point bending test was adopted to determine flexural strength with 100 \(\times\) 100 \(\times\) 400 mm\({}^{3}\) specimen.