## 3 Results and Discussion
### Marshall Stability Test Results  
The Marshall stability test was performed to determine the optimum bitumen content and the stability and flow values of the mixtures in the test plan in accordance with ASTM D6927 [52]. Each test sample was prepared using a mixture of 1150 g of aggregate and filler in accordance with the granulometry specifications detailed in Table 3. The bitumen percentage was determined based on the aggregate weight, and the optimum bitumen content was calculated using seven sets of Marshall test samples. These samples were prepared using bitumen ratios of 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, and 6.5% of the aggregate \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Experiment No** &
\begin{tabular}{c} **Elongation** \\ **(mm)** \\ \end{tabular} & **d (mm)** & **R\({}_{\text{E}}\) (\%)** & **S/N** \\ \hline
1 & 200 & 8 & 4.00 & 12.04 \\
2 & 200 & 9 & 4.50 & 13.06 \\
3 & 200 & 10 & 5.00 & 13.98 \\
4 & 200 & 11 & 5.50 & 14.81 \\
5 & 200 & 18 & 9.00 & 19.08 \\
6 & 200 & 20 & 10.00 & 20.00 \\
7 & 200 & 29 & 14.50 & 23.23 \\
8 & 200 & 30 & 15.00 & 23.52 \\
9 & 200 & 27 & 13.50 & 22.61 \\
10 & 200 & 28 & 14.00 & 22.92 \\
11 & 200 & 26 & 13.00 & 22.28 \\
12 & 200 & 29 & 14.50 & 23.23 \\
13 & 200 & 25 & 12.50 & 21.94 \\
14 & 200 & 24 & 12.00 & 21.58 \\
15 & 200 & 22 & 11.00 & 20.83 \\
16 & 200 & 20 & 10.00 & 20.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Elastic recovery results and S/N values. Figure 10: Performance statistics for elastic recovery for all levels. weight, and they were subjected to 75 blows of the [PERSON] hammer on each face. The stability and flow values of the samples were determined through the Marshall stability test. Based on the obtained results, the optimum bitumen content (OBC) was found to be 4.85%, which corresponds to a void ratio of 4% and the highest stability value. According to the experiment plan with the optimum bitumen content, 16 \(\times\) 3 = 48 mixtures were prepared, and Marshall samples were cast as shown in Figure 11.  
Table 14 provides values for stability, flow, Marshall quotient (MQ), air void (V\({}_{\text{a}}\)), voids in mineral aggregate (VMA), voids filled with asphalt (VFA), and their corresponding S/N values. Using the \"larger is better\" performance statistic, the optimum levels that maximize stability were A2, B1, C2, and D1, as seen in Table 15. A stability value of 1286.57 kg was obtained after the verification experiment. The S/N value corresponding to this result was 62.190. This value fell between 62.139 and 63.220 at the 95% confidence level. Temperature  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Experiment No**} & \multicolumn{2}{c}{**Marshall Stability**} & \multicolumn{2}{c}{**Flow**} & \multicolumn{2}{c}{**MQ**} & \multicolumn{2}{c}{**V\({}_{\text{a}}\)**} & \multicolumn{2}{c}{**VMA**} & \multicolumn{2}{c}{**VFA**} \\ \cline{2-13}  & **kg** & **S/N** & **mm** & **S/N** & **kg/mm** & **S/N** & **\%** & **S/N** & **\%** & **S/N** & **\%** & **S/N** \\ \hline
1 & 1069.78  
had the most significant impact on stability, with a value of 0.828. This was followed by additive ratio, mixing speed, and mixing time. Bitumen pavements can withstand deformations until the load value of stability is reached. The vertical deformation that occurs at this point is called the flow value [75]. The stability value increased by up to 0.3% with the Cecabase RT BIO10 additive, preventing the mixture from failing due to decreased adhesion and cohesion resulting from reduced mixing temperature [76]. However, the stability values decreased at higher rates. Despite this decrease, the stability values obtained were higher than those of the samples prepared with virgin bitumen. The increase in additive content above 0.3% might have reduced the mixture's stability by making it more susceptible to the mixing temperature [76]. In the experiments based on the test plan, the highest stability value was 1336.59 kg, an increase of 29.515% compared to the mixtures prepared with virgin bitumen.