## 3 Results and Discussion  
### Compaction Properties of OGFC-5 UPFC with Different Thickness  
According to the compaction parameters in Table 3, different OGFC-5 UPFC samples were prepared to monitor the compaction process. The simulated field compaction results for the OGFC-5 UPFC under different compaction parameters are presented in Table 6 and Figure 5. The curve of the specimen height with respect to the gyratory number is shown in Figure 5a. According to Equation (4), linear regression analysis was performed on the specimen height and gyratory number, as shown in Figure 5b. The results of the linear regression analysis are presented in Table 7.  
\[\ln H(N)=a\ -k\ln(N) \tag{4}\]  
Figure 4: Different radius cross sections used in analysis on horizontal AV variability: (**a**) \(1/4\) radius; (**b**) \(1/2\) radius; (**c**) \(3/4\) radius; (**d**) full radius.  
Figure 3: CT scanning.  
where \(a\) and \(k\) correspond to the fitting parameters, and \(N\) and \(H(N)\) represent the gyratory number and height at gyratory number of \(N\), respectively. The parameters \(a\) and \(k\) reflect the initial density and difficulty of the compaction process, respectively. The larger the \(a\) and \(k\) values, the easier it is for the specimen to be compacted to the target height [37].  
As shown in Table 6, 5 test specimens, S100/15, S100/15-1, S100/15-2, S150/15, and S100/20, were insufficiently compacted and did not achieve the target compaction thickness after 200 gyratory numbers. In addition, the AV contents of the five specimens were 27.2%, 27.3%, 27.3%, 26.5%, and 25.4%, respectively, which were much higher than the design AV requirement of 18% for UPFC mixes designed using the MCM.  
According to Table 7, for the 15 mm UPFC specimen, the \(a\) and \(k\) values of all 15 mm \(\times\) 100 mm (height and diameter, respectively) test samples showed little difference, and increasing the vertical pressure and the internal gyration angle had little effect on the compaction height. The S150/15 specimen had the smallest k value, indicating that the S150/15 specimen was the most difficult to compact to 15 mm. In this regard, the increased radius of the specimen made the compaction pressure more dispersed and increased the difficulty of compaction of the UPFC specimen. In addition, a decrease in the compaction thickness decreased the values of parameters \(a\) and \(k\). The initial compaction density of the UPFC specimen decreased, which resulted in compaction difficulties. At the same time, Figure 5a exhibits that the smaller the compaction thickness, the more gyratory numbers were required. This could be because the pressure inside the specimen was non-uniform as the target compaction height decreased. The aggregates in one or several regions were stabilized and bore the main pressure, whereas the other unstabilized regions received less force, and it was difficult for the particles to move, rotate, and be sufficiently compacted.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Specimen ID** & **S100/15** & **S100/15-1** & **S100/15-2** & **S150/15** & **S100/20** & **S100/25** & **S100/40** & **S100/63.5** \\ \hline Gyratory number & 200 & 200 & 200 & 200 & 200 & 128 & 80 & 32 \\ Height & 16.7 & 16.7 & 16.5 & 16.8 & 21.7 & 25.2 & 40.2 & 63.4 \\ AV ratio & 27.2\% & 27.3\% & 27.3\% & 26.5\% & 24.4\% & 18.6\% & 18.3\% & 19.1\% \\ \hline \hline \end{tabular}
\end{table}
Table 6: The compaction results of different SGC compaction parameters.  
Figure 5: Compaction curves: (**a**) common coordinates; (**b**) semi-logarithmic coordinates.