## 2 Experimental Design
### Methodology and Testing
#### 2.3.3 AV Characterization of OGFC-5 UPFC Based on CT Scanning  
The OGFC-5 mixture possesses an AV content of 18-25%. Internal AV characteristics (such as the AV content and size) are critical for noise reduction and drainage improvement. In view of this, 15 mm OGFC-5 specimens were formed using the SGC and RWC methods to simulate the field core samples of the UPFCs. Similar to the SGC specimen, the mix masses of the RWC specimen were calculated according to the equivalent volume of the Marshall specimens. The roller-forming equipment used was an Italian control pavement roller, as shown in Figure 2. A 400 mm \(\times\) 300 mm \(\times\) 15 mm (length, width, height, respectively) cuboid specimen was fabricated using a height control procedure, and core samples were drilled to obtain cylindrical specimens. The samples are listed in Table 5. According to the OFGC-5 UPFC mix design results using the MCM, 15 mm UPFC specimens formed via SGC and RWC that simulate the field compaction were not compacted to the target AV content and height, which indicated that the MCM-designed UPFC mixes did not conform to the field compaction.  
In the experiment, the PrecisionIICT for industrial use produced by YXLON was used to scan the samples, and pictures were obtained every 0.1 mm along the height of the samples, as shown in Figure 3. These obtained pictures were automatically handled by a macro, and then Image-Pro Plus software (IPP 6.0.0.260) was applied to obtain the AV characteristics. According to the study conducted by [PERSON] et al. [35], the average AV contents of the single and total images were determined using Equations (1) and (2), respectively. In addition, because the AV diameter largely depends on the packing degree of the granular skeleton inside the UPFC samples, the average AV diameter should be analyzed [36]. Therefore, the AV size decreased with increasing packing and particle contact. Equation (3) was adopted to calculate the average AV radius of the \(i\)-th image. Furthermore, the horizontal variability in the AV ratios and the mean AV diameter in the  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Specimen ID** & **Modding Method** & \begin{tabular}{c} **Target Specim Size** \\ **(Diameter \(\times\) Height)** \\ \end{tabular} & \begin{tabular}{c} **Measured Specim Size** \\ **(Diameter \(\times\) Height)** \\ \end{tabular} & \
\begin{tabular}{c} **Target AV** \\ **Ratio (\%)** \\ \end{tabular} &
\begin{tabular}{c} **Measured AV** \\ **Ratio (\%)** \\ \end{tabular} \\ \hline M100/63.5 & Marshall & 101.6 mm \(\times\) 63.5 mm & 101.6 mm \(\times\) 63.0 mm & & 17.9 \\ S100/15 & SGC & 100 mm \(\times\) 15 mm & 100 mm \(\times\) 16.7 mm & & 27.2 \\ S150/15 & SGC & 150 mm \(\times\) 15 mm & 150 mm \(\times\) 16.8 mm & & 26.5 \\ R100/15 & RWC & 100 mm \(\times\) 15 mm & 100 mm \(\times\) 17.0 mm & & 27.4 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Summary of different test specimens.  
Figure 2: Controls pavement roller.  
cross sections of different radii (Figure 4) were investigated to obtain the horizontal AV distribution of the Marshall specimens and simulated field cores.  
\[\text{AV}_{i}=\frac{\text{A}_{vi}}{\text{Ai}} \tag{1}\]  
\[\text{AV}_{s}=\frac{\sum\limits_{i=1}^{n}\text{AV}_{i}}{N} \tag{2}\]  
\[d_{i}=2\sqrt{\frac{\text{A}_{vi}}{\pi n}} \tag{3}\]  
where A\({}_{i}\), A\({}_{vi}\), AV\({}_{i}\), \(d_{i}\), and \(n\) are the cross-sectional area, AV area, AV ratio, AV mean diameter, and AV number of the \(i\)-th image, respectively. The AV\({}_{s}\) and \(N\) correspond to the AV rate and total number of CT images of the test specimen, respectively.