## 3 VVCM Evaluation
### Mechanical Properties  
To assess the reliability of VVCM, the mechanical strength of both VVCM and PCT specimens was compared to that of field core samples. To mitigate testing discrepancies, both field and indoor LSAM-50 samples shared identical material compositions, as detailed in Tables 1 and 2, and maintained consistent aggregate gradations, as shown in Table 3.  
The mechanical strengths of the LSAM-50 asphalt mixture for VVCM, PCT specimens, and field core samples are presented in Table 6. Each test was conducted three times. \(\overline{R}\) is the mean intensity value, and \(C_{v}\) is the coefficient of variation.  
As indicated in Table 6, the ratios of \(R_{c}\) and \(R_{T}\) between the VVCM specimens and the field core samples are 91.8% and 89.9%, respectively, while those for the PCT specimens are 74.8% and 79.8%, respectively. This suggests that the mechanical strength correlation between the VVCM specimens and the field core samples is stronger than that between the PCT specimens and the field core samples. Furthermore, the \(R_{c}\) and \(R_{T}\) values of the VVCM specimens are 1.23 and 1.13 times those of the PCT specimens, respectively, and the \(C_{v}\) value of the VVCM specimens is notably lower. This indicates that the mechanical strength of the VVCM specimens exceeds that of the PCT specimens and more closely approximates the mechanical strength of the field core samples, with more stable test results. Therefore, VVCM specimens produced in laboratory tests are more reflective of actual field conditions.  
The higher mechanical strength observed in VVTM specimens can be attributed to the sinusoidal excitation force they experience during formation. This force ensures  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Strength Indexes**} & \multirow{2}{*}{**Forming Method**} & \multicolumn{2}{c}{**Parallel Specim Strength Test Value (MPa)**} & \(\overline{R}\) & \(C_{v}\) \\ \cline{3-6}  & & **1** & **2** & **3** & **(MPa)** & **(\%)** \\ \hline \multirow{3}{*}{60 \({}^{\circ}\)C \(R_{c}\)} & Core samples & 3.65 & 3.87 & 3.46 & 3.66 & 5.6 \\  & VVCM & 3.32 & 3.49 & 3.26 & 3.36 & 3.6 \\ \cline{1-1}  & PCT & 3.01 & 2.49 & 2.72 & 2.74 & 9.5 \\ \hline \multirow{3}{*}{60 \({}^{\circ}\)C \(R_{T}\)} & Core samples & 0.225 & 0.240 & 0.220 & 0.228 & 4.6 \\ \cline{1-1}  & VVCM & 0.213 & 0.199 & 0.204 & 0.205 & 3.4 \\ \cline{1-1}  & PCT & 0.178 & 0.203 & 0.166 & 0.182 & 10.4 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Comparison of the mechanical strengths of VVCM specimens and PCT specimens.  
Figure 3: Specim appearance.  
substantial relative movement between coarse and fine aggregates. While achieving optimal compaction, it minimizes damage to the internal coarse aggregate, leading to a more robust aggregate framework that provides greater internal friction resistance. In contrast, PCT specimens are exposed solely to a unidirectional vertical pressure during their formation. This limits the lateral relative position change between aggregates, reducing the efficiency of the compaction process. Additionally, this vertical pressure compromises the coarse aggregate structure, resulting in fractures in larger-sized stones and an increase in slip surfaces, consequently diminishing their mechanical strength.  
The degree of coarse aggregate damage in VVTM specimens is generally lower, leading to relatively stable test values for specimen strength. In contrast, specimens formed by the static pressure method exhibit varied, and generally higher, degrees of coarse aggregate damage. This results in a pronounced reduction in the interlocking force provided by the coarse aggregate framework, and the extent of this reduction is inconsistent among specimens. This elucidates why the coefficient of variation for the mechanical strength of VVTM specimens is significantly lower than that of PCT specimens.