## 3 Results
### Polybutadiene and Polystyrene Indices  
The following section presents the relative changes in the polybutadiene and polystyrene indices in polymer-modified asphalt binders, relative to the non-aged reference binders (PMB without additives). The corresponding statistical models approximating the values of the indices, and their regression coefficients are evaluated in the provided tables. Figures 5 and 6 present the values of the polybutadiene index and polystyrene indices, respectively, and their changes in the 45/80-55 asphalt binder as a function of the amount of the investigated additives, while Table 8 shows the statistical analysis of these effects. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Asphalt**} & \multicolumn{2}{c}{**Additive (\%)**} & \multicolumn{3}{c}{\(\mathrm{I_{C=O}}\)} & \multicolumn{3}{c}{\(\mathrm{I_{S=O}}\)} \\
**Binder** & **A** & **B** & **Non-Aged** & **RTFOT** & **RTFOT+PAV** & **Non-Aged** & **RTFOT** & **RTFOT+PAV** \\ \hline \multirow{5}{*}{50/70} & 0.0 & 0.0018 & 0.0027 (50\%) & 0.0037 (10\%) & 0.0043 & 0.005 (16\%) & 0.0069 (60\%) \\  & 0.0 & 2.0 & 0.0004 (\(-78\%\)) & 0.0013 (  
As it is presented in the plots in Figure 5, the additives altered the measured values of the polybutadiene index to a lesser extent than was seen in the case of the carbonyl and sulfoxide indices. The largest effects of the additives were observed in the non-aged binder and after the PAV ageing. Before ageing, additive A caused a substantial increase in the I\({}_{\text{PB}}\) index value, while additive B decreased it to some extent. After RTFOT ageing, both additives had far less impact on this index. The PAV ageing significantly changed the way the additives affected the values of the polybutadiene index. The use of both additives caused a decrease in the index after long-term ageing, which was largest when both additives were used at the highest concentrations simultaneously. Figure 5: Surface plots of the changes in polybutadiene index values in the 45/80-55 asphalt binder in response to the investigated additives and laboratory ageing. Figure 6: Surface plots of the changes in polystyrene index values in the 45/80-55 asphalt binder in response to the investigated additives and laboratory ageing. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**PMB Indices** & \multicolumn{3}{c}{**I\({}_{\text{PB}}\) (45/80-55)**} & \multicolumn{3}{c}{**I\({}_{\text{PS}}\) (45/80-55)**} \\
**Effect:** & **Ageing: None** & **Ageing: RFTOT** & **Ageing: RFTOT+PAV** & **Ageing: RFTOT** & **Ageing: RFTOT+PAV** \\ \hline Intercept & 0.004 *** & 0.004 *** & 0.003 *** & 0.002 *** & 0.002 *** & 0.002 *** \\ Additive A & 0.004 *** & 0.00002 & \(-\)0.003 *** & 0.0004 & \(-\)0.001 *** & \(-\)0.002 *** \\ Additive B & \(-\)0.001 *** & 0.0002 *** & \(-\)0.001 * & \(-\)0.0003 *** & 0.0002 *** & \(-\)0.00002 \\ (Additive A)\({}^{2}\) & \(-\)0.009 *** & \(-\)0.004 *** & 0.008 *** & \(-\)0.002 * & 0.001 & 0.005 *** \\ (Additive B)\({}^{2}\) & 0.0001 *** & \(-\)0.0001 *** & 0.00001 & 0.0001 *** & \(-\)0.0001 *** & \(-\)0.00002 \\ A:B interaction & 0.001 *** & 0.001 *** & \(-\)0.0002 * & 0.0003 *** & 0.0004 *** & \(-\)0.0002 * \\ \hline Observations & 27 & 27 & 27 & 27 & 27 & 27 \\ R\({}^{2}\) & 0.954 & 0.856 & 0.922 & 0.821 & 0.894 & 0.960 \\ Adjusted R\({}^{2}\) & 0.943 & 0.822 & 0.903 & 0.778 & 0.869 & 0.950 \\ \hline \hline \end{tabular} Note: \(\dashp\leq 0.1\); \(\dashp\leq 0.05\); \(\dashp\leq 0.01\); \(\dashp\leq 0.001\).  
\end{table} 
Table 8: A summary of the statistical analysis (analysis of variance) on the investigated additives’ effects on the values of the polybutadiene index measured in the 45/80-55 asphalt binder. The effects of the investigated additives on the polystyrene index were similar to those on the polybutadiene index as shown in Figure 6. Also in this case, the additives changed the measured values of the polystyrene index, but to a lesser extent than in the case of the carbonyl and sulfoxide indices.