# Assessing the Compaction Quality of Dolomitic Asphalt Pavements Using Ground Penetrating Radar
## 7 Discussion
Finally, for asphalt pavements with aggregate sizes ranging from 11 mm to 25 mm, composed of limestone-dolomite, and within the same percentage of asphalt binder content as detailed in (Table 5), we propose a generalized function between the \(\varepsilon\) and \(G_{\text{mb}}\) for these specific conditions (Figure 10). The influence of the asphalt content on these correlations further highlights the necessity of considering binder properties in future analyses. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Course Type** & **Mean RD** & **Min RD** & **Max RD** & **Range RD** & **SD** \\ \hline \multirow{3}{*}{Section I.} & Wearing course & 0.949 & 0.944 & 0.956 & 0.012 & 0.033 \\ \cline{2-7}  & Binder course & 0.964 & 0.960 & 0.971 & 0.011 & 0.022 \\ \cline{2-7}  & Base course & 0.976 & 0.972 & 0.978 & 0.006 & 0.041 \\ \hline \multirow{3}{*}{Section II.} & Wearing course & 0.944 & 0.942 & 0.954 & 0.012 & 0.037 \\ \cline{2-7}  & Binder course & 0.963 & 0.962 & 0.974 & 0.012 & 0.029 \\ \cline{2-7}  & Base course & 0.974 & 0.971 & 0.977 & 0.006 & 0.043 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mean, minimum, and maximum values and range and standard deviation of RD for investigated asphalt layers. Figure 9: Comparison of relationship between \(\varepsilon\) and \(G_{\text{mb}}\) resulting from this study and other authors’ studies [32; 33; 34]. Based on our study, reflection amplitudes become relatively constant after six compaction passes. This finding was reinforced by [PERSON] et al. [22], indicating that the maximum mixture densities can be achieved when the number of compaction passes reaches six. Another study by [PERSON] et al. [35] revealed that the rolling resistance and energy utilization coefficient values were less than 0 when the numbers of roller passes were 7, 9, and 10, since the value of the compaction energy density was at a very low level when the number of roller passes exceeded 6. Figure 10: Plot of function between \(\varepsilon\) and G\({}_{\text{mb}}\) derived from our study and [PERSON] et al. [34]. \begin{table}
\begin{tabular}{c c c c c} \hline  & **This Study** & **[PERSON] et al. [33]** & **[PERSON] et al. [34]** & **[PERSON] et al. [32]** \\ \hline Mineral composition & Dolomitic limestone & Granite & Limestone & Sandstone \\ \hline Aggregate size & AC 11, AC 22 & AC 13–19 mm & AC 13, AC 20, AC 25 & AC 20 \\ \hline Asphalt Binder & 4.1\% & 5.1\% & 4.5\%, 4.1\%, 3.8\% & 4\%, 5\%, 6\% \\ \hline Mean \(\varepsilon\) & 2.36 & 2.23 & 2.44 & 2.35 \\ \hline G\({}_{\text{mb}}\) & 5.45 & 5.11 & 6.43 & 4.44 \\ \hline Other & \begin{tabular}{c} Binder RD: \\ 1.050 g/cm\({}^{3}\) \\ \end{tabular} & \
\begin{tabular}{c} 35\% Recycled Asphalt \\ Pavement (RAP) \\ \end{tabular} &
\begin{tabular}{c} 8\% Air voids, \\ 0.44\% Moisture content \\ \end{tabular} & 2–10\% Air voids \\ \hline \end{tabular}
\end{table} 
Table 5: Mineral composition, aggregate size, asphalt binder, mean \(\varepsilon\), G\({}_{\text{mb}}\), and other information regarding studies plotted on Figure 9.  
Despite the observed variations, the RD of asphalt layers in the investigated road section ranged between 0.94 and 0.98, which is considered close to the optimum value. These results are consistent with those reported by [PERSON] et al. [33], who found that over 80% of the surveyed area exhibited RD values between 0.90 and 0.95. Another study by [PERSON] et al. [35] found that the degree of compaction ranged between 0.93 and 0.99; when they used different rollers, they found that the compaction effect for the same number of roller passes was different. [PERSON] et al. [36] found that approximately 99% of three other sites were compacted between a density of 0.93 and 0.96 by using the intelligent asphalt compaction analyzer (IACA); they also found that less than 1% of the completed pavement was undercompacted. Finally, [PERSON] et al. [37] found that the RD values ranged between 0.91 and 0.93 when using a nonnuclear density gauge.