## 3 Results and Discussion  
### Penetration and Softening Point Test Results  
Figure 5 presents the results based on the experiment plan given in Table 5 indicating the penetration values before and after RTFOT. The \"larger is better\" performance statistic that maximizes the result was used for penetration tests, and the \"smaller is better\" performance statistic that minimizes the result was used for softening point tests. After calculating S/N values, the average S/N effects were calculated to determine optimum levels for penetration tests before RTFOT, as presented in Table 7.  
The optimum levels for penetration before RTFOT were found to be A3, B1, C4, and D2, as given in Table 7. The parameters with the highest impact on penetration were the Cecabase ratio, time, speed, and temperature, respectively. The Cecabase ratio impacted the penetration value, increasing it up to the 0.4% level, helping increasing the bitumen flexibility and softness but also causing a slight decrease at the 0.5% level. The penetration \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{5}{c}{**Levels**} \\ \cline{2-5}  & **1** & **2** & **3** & **4** \\ \hline (A) Cecabase RT BIO 10 (\%) & 0.00 (A1) & 0.30 (A2) & 0.40 (A3) & 0.50 (A4) \\ (B) Temperature (\({}^{\circ}\)C) & 110 (B1) & 120 (B2) & 130 (B3) & 140 (B4) \\ (C) Time (min) & 15 (C1) & 20 (C2) & 25 (C3) & 30 (C4) \\ (D) Speed (RPM) & 1000 (D1) & 2000 (D2) & 3000 (D3) & 4000 (D4) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Parameters and levels for the Taguchi method. Figure 5: Penetration test results. value increased as the mixing time increased, ensuring better dispersion throughout the bitumen and leading to a consistent and uniform mixture. Moreover, the penetration value also increased as the mixing speed was raised to 2000 RPM maintaining the structural integrity of the bitumen. However, the penetration value decreased at 3000 and 4000 RPM; higher speeds might have induced too much shear stress leading to a breakdown of the bitumen structure. Considering the experiment plan in Table 5, it is seen that there is no experiment with optimum parameters. Therefore, a sample with the relevant parameter values (A3, B1, C4, D2) was prepared to verify the result. At the end of the verification experiment, a penetration value of 72.4 (0.1 mm) was obtained. The S/N value corresponding to this result was 37.20. As indicated in Table 8, this value should fall within the interval of 37.180 and 38.005 at a 95% confidence level. Therefore, the result is correct within the 95% confidence interval. The penetration values before RTFOT varied between 58.90 and 71.53 (0.1 mm). In the experiments conducted based on the experiment plan, the highest penetration value was 71.53 (0.1 mm), an increase of 6.459% compared to virgin bitumen. The penetration value calculated according to the optimum levels that maximize the penetration value was 75.788 (0.1 mm), an increase of 12.88% compared to virgin bitumen. [PERSON] et al. [36] reported a 3.92% increase in the penetration of 50/70 bitumen with Cecabase RT BIO10 additive. [PERSON] et al. [38] found that the additive increased the penetration value of virgin bitumen by 14.11%. Based on the results shown in Table 9, the optimum penetration levels after RTFOT were found to be A3, B4, C4, and D2. The penetration optimum levels for the temperature parameter were found to be B1 and B4 before and after aging. Higher temperature (B4) helped to ensure sufficient workability and penetration by compensating for the effects of aging. After conducting the verification experiment, the obtained penetration value was 45.2 (0.1 mm), corresponding to a S/N value of 33.10. The confidence interval of S/N values at a 95% confidence level was between 32.998 and 33.853, as shown in Table 9. Since the test result fell within this range, it can be concluded that it was accurate within the 95% confidence level. Among the parameters studied, the Cecabase additive was found to be the most effective, with a value of 0.561.