## 3 Results and Discussion
### Compaction Characteristics  
The results of the tests conducted are presented in Table 2 and Figure 4. For mixtures with natural aggregate (0%/C, 3%C, 5%C, 7%C), similar results are obtained with both compaction methods. The difference between the MDD values obtained is less than those of OMC. For cement-bound mixtures, similar MDD values (third decimal difference) are obtained, but Proctor compaction required a higher water content. Generally, the vibrating hammer compaction method provides a lower OMC for the same MDD values. The similarity of the results obtained leads to the conclusion of the high comparability of the two test methods for mixtures with natural aggregate. It can be concluded that the vibrating hammer compaction method can be used as an alternative to the modified Proctor compaction method since it is more practical and less time-consuming. A similar observation is presented in [20], where the authors also state that, compared with the standard Proctor method, higher OMC and MDD values should be expected when using the vibrating hammer compaction method. Also, an expected increase in OMC and MDD is observed with the increase in cement content for both the compaction methods used. The cement hydration reaction and cement paste creation require more water for a higher cement content within the mixture [42]. The vibrating hammer is a less time-consuming method, considering compaction in 3 layers for 60 s per layer and time taken for filling the mould with material, gives about 5 min per specimen. So the lower OMC could be the result of less time being available for the cement's initial setting time and less water being used for initial hydration. To be more precise, cement has more time available for hydration in the Proctor compaction method. Unlike the 60 s for the vibrating hammer method, 56 blows per layer take longer. With a longer compaction of the one layer, the Proctor method still requires a larger number of layers (5), which makes this process longer still and takes approximately 15 min per \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & **0\%C** & **3\%C** & **5\%C** & **7\%C** & **5\%C + 20\%R** & **5\%C + 30\%R** & **5\%C + 60\%R** \\ \hline
**OMC [\%]** & **4.79/4.72** & **4.91/5.15** & 5.35/5.87 & 5.53/6.10 & 5.32/5.53 & 5.21/5.13 & **4.94/4.94** \\ \hline
**MDD [g/cm\({}^{3}\)]** & **2.01/1.97** & **2.08/2.09** & **2.12/2.12** & **2.15/2.15** & **2.10/2.06** & **2.03/2.03** & **1.87/1.89** \\ \hline \(\rho\) [g/cm\({}^{3}\)] &
\begin{tabular}{c} **not** \\ **applicable** \\ \end{tabular} & **2.17/2.28** & **2.21/2.29** & **1.96/2.37** & **2.18/2.23** & **2.07/2.18** & **1.96/2.05** \\ \hline
**CBR [\%]** & **101/98** & \begin{tabular}{c} **not** \\ **applicable** \\ \end{tabular} & **not** & \
\begin{tabular}{c} **not** \\ **applicable** \\ \end{tabular} & **not** &
\begin{tabular}{c} **not** \\ **applicable** \\ \end{tabular} & **not** & **not** & **not** & **not** \\ \hline
**f\({}_{\text{c}}\) [MPa]** &
\begin{tabular}{c} **not** \\ **applicable** \\ \end{tabular} & **4.11/4.06** & **7.59/7.60** & **12.99/12.92** & **1.89/3.13** & **1.33/2.48** & **0.49/0.94** \\ \hline \end{tabular}
\end{table} 
Table 2: Results obtained by two test methods, vibrating hammer (marked green) method and Proctor (marked red), respectively. Figure 4: (**a**) Optimal moisture content (OMC) and (**b**) maximum dry density (MDD) for UBC and CBC mixtures. sample. From this discussion, it can be concluded that the specimen compacted by the Proctor method has about 3 times more time for cement hydration which requires more water, compared to vibrating hammer specimens. However, similar strength characteristics are obtained and high comparability is observed. For higher cement content mixtures, the OMC difference depending on the laboratory compaction method used can reach 0.6%, so the laboratory compaction method should be chosen carefully, particularly if moisture-susceptible materials are used.