# Assessing the Compaction Quality of Dolomitic Asphalt Pavements Using Ground Penetrating Radar
## 6 Results  
### Comparability and Accuracy of \(\varepsilon\) Measurements  
We conducted a comparative study using field and laboratory validation to determine the most efficient measurement approach--specifically, the horn antenna or PaveScan--for further analysis of pavement characteristics. By comparing the results (Table 1), we found that the average \(\varepsilon\) values of the base course, binder course, and wearing course, calculated by the horn antenna and PaveScan for Sections I. and II, yielded similar results. When validating the above results of the base course and binder course layers using cores (the wearing course was not cored), it was found that for Section I., the relative deviation of the PaveScan dielectric values from the core-derived laboratory data was considerably higher than the relative deviation experienced in the case of the GPR horn antenna measurements, as shown in Table 2, for Section II. It was found that the relative deviation of the PaveScan dielectric values from the core-derived data was also considerably higher than the relative deviation experienced based on the horn antenna measurements, \begin{table}
\begin{tabular}{c c c c c} \hline  & \multicolumn{2}{c}{**Section I.**} & \multicolumn{2}{c}{**Section II.**} \\ \hline
**Layer** & **Horn Antenna** & **PaveScan** & **Horn Antenna** & **PaveScan** \\ \hline Base Course & 5.87 & 5.86 & 5.65 & 5.67 \\ \hline Binder Course & 6.1 & 6.09 & 5.63 & 5.76 \\ \hline Wearing Course & 4.42 & 4.73 & 4.52 & 4.23 \\ \hline \end{tabular}
\end{table} 
Table 1: Comparison of average \(\varepsilon\) values for different pavement layers using horn antenna and PaveScan in Sections I. and II. as shown in Table 2. It was also noticed that the dielectric constants of the surface course had the lowest values, which were surveyed by either the horn antenna or the PaveScan device, probably because the smallest grain size characterized this layer compared to the other layers. In general, the horn antenna values were closer to the core data. In other words, horn antenna measurements can estimate dielectric constants very well, and their accuracy is higher than PaveScan measurements. However, in the case of both devices, the assessment of \(\varepsilon\) was made using the SR method, while the laboratory assessment was made using the TOF method. Nevertheless, the results underline the flexible use of horn antenna systems in determining the \(\varepsilon\) of pavement layers (Figure 5). To assess the accuracy of the horn antenna and PaveScan instruments applied in the field, a detailed comparison was made between the laboratory test measurements, performed for each layer separately, and the field data obtained by the horn antenna and PaveScan measurements after the compaction of each layer (Figure 6). All of the core samples were applied to investigate comparability. Laboratory measurements were formulated to provide an independent \(\varepsilon\) value for the comparisons. Initially, we established a relationship between the on-site \(\varepsilon\) values obtained by the horn antenna measurements just before the coring was made using the SR method and the \(\varepsilon\) values obtained in the laboratory from the cores themselves by the ground-coupled antenna using the TOF method (Figure 6a). The results showed a direct proportional relationship with a high coefficient of determination (R\({}^{2}\) = 0.83), indicating a strong correlation between the \(\varepsilon\) values obtained with the two approaches. Subsequently, we plotted the at-a-point results of the PaveScan measurements using the SR method against the laboratory data (Figure 6b). A very similar coefficient of determination was obtained in this case (R\({}^{2}\) = 0.82). However, the regression line in terms of the horn antenna results approximates the line of equality much better than the regression obtained using the PaveScan measurements; thus, the \(\varepsilon\) obtained by using the horn antenna exhibits closer agreement with the laboratory measurements.