# Assessing the Compaction Quality of Dolomitic Asphalt Pavements Using Ground Penetrating Radar
## 6 Results
### Effect of \(G_{\text{mb}}\), Aggregate Size, and Compaction on \(\varepsilon\)  
By understanding how the \(G_{\text{mb}}\) and aggregate size affect dielectric values, a valuable tool can be developed to assess the compaction quality, the material homogeneity, and the prediction of the structural performance of the pavement. Nuclear gauge \(G_{\text{mb}}\) data was plotted against the GPR results on \(\varepsilon\) to establish relationships among the above parameters (Figure 7). The \(G_{\text{mb}}\) was measured on each layer after each compaction pass. In the case of each layer, a clear, direct relationship was found between density and \(\varepsilon\), and the coefficient of determination was, in most cases, higher than 0.9. The layers  
Figure 6: A comparison of \(\varepsilon\) from the (**a**) SR horn antenna (field measurement) and TOF (laboratory measurement) methods; (**b**) SR PaveScan (field measurement) and TOF (laboratory measurement) methods using the core samples. The orange line represents the line of equality. appeared at different parts of the graph, and the slope of the linear functions between the plotted parameters was also different for each. This occurs because the variation in slope indicates that different asphalt layers have unique dielectric-density relationships, which are influenced by material properties such as aggregate size (d\({}_{\rm max}\)), compaction level, and asphalt content. Understanding these distinctions is important for accurately interpreting the GPR results. The highest G\({}_{\rm mb}\) and \(\epsilon\) values were found in terms of the sub-base course (\(\rho\): 2.60-2.80 g/cm\({}^{3}\) and \(\epsilon\): 8.77-10.88); the binder and base course exhibited medium values ((\(\rho\): 2.30-2.54 g/cm\({}^{3}\) and \(\epsilon\): 5.13-6.46)) on average; and the wearing course had the lowest values (\(\rho\): 2.11-2.29 g/cm\({}^{3}\) and \(\epsilon\): 3.77-4.70). The results show a clear relationship between the aggregate size (d\({}_{\rm max}\)) and the dielectric values. We can read from Figure 7 that larger aggregates generally lead to a higher G\({}_{\rm mb}\) because they reduce the overall porosity. However, smaller aggregates allow for a more uniform and efficient compaction process, which enhances density but may also retain a higher concentration of air voids if not adequately compacted. The compaction process was efficient in the case of the wearing course, which contained smaller aggregates. However, it did not fully eliminate the air voids, leading to a slightly lower G\({}_{\rm mb}\) than the coarser layers. In contrast, the binder course and base course layers, characterized by a moderate aggregate size, contained moderate air voids. Consequently, the binder course and base course showed better compaction, leading to higher density than the wearing course. The high dielectric values of the sub-base course are primarily due to its larger aggregate size, which influences the air void distribution and compaction efficiency. While dolomitic aggregates may have a naturally higher dielectric constant, the dominant factor in this context is the aggregate size, as it directly affects the layer's density and air void content. Six compaction passes reached the maximum density and dielectric values (Table 3). We  
Figure 7: The relationship between the G\({}_{\rm mb}\), measured by the nuclear gauge, and the \(\epsilon\), measured by the horn antenna, during the compaction process of each layer (1, 2, 3, 4, 5, 6, and 7 correspond to the number of compaction passes). found that the \(\varepsilon\) for all layers reached a relatively stable value, indicating the achievement of maximum mixture densities. These compaction curves can serve as a valuable reference for determining the optimal number of compaction passes required to achieve the maximum mixture density. Additionally, the point at which the dielectric and density values show negligible changes--observed after six compaction passes--could provide a reference for future research studies.