# Data-Driven Prediction of Binder Rheological Performance in RAP/RAS-Containing Asphalt Mixtures
## 3 Results and Discussion
### Rheological, Chemical, and Thermal Characterization of the Extracted Binders  
The rheological properties of the extracted binders were characterized and evaluated using FTIR chemical indices and thermal residue content. Figure 3 shows random groups of plant- and lab-extracted binders. In Figure 3a, the first and second groups represent plant-extracted binders (P2, P3, P8, and P9), whereas the third group represents laboratory-extracted binders (L5 and L15). The diameter of the bubbles reflected the rutting parameter. The larger the diameter, the greater the rutting parameter value. The first group of extracted binders containing RAS demonstrated the highest rutting performance. The second group of extracted binders, which included RAP, exhibited the lowest rutting parameters among all groups. The first sample in the third group of extracted binders (L5) contained the same components as the second group, but their corresponding mix was produced in the laboratory, resulting in similar rutting parameters. Binders with the highest rutting parameters (P2 and P3) had the highest aging indices in Figure 3a (\(I_{CO}+I_{SO}\)), the lowest aromatic plus aliphatic indices in Figure 3b (\(I_{CC}+I_{CH}\)), and the highest R% in Figure 3c. Higher aging indices and residue percentages indicate that the binders are more aged and contain more asphaltenes. Furthermore, during aging, aliphatic compounds are converted to aromatics [12; 15; 28; 52]. Thus, binders exhibiting the greatest stiffness and rutting parameters demonstrated the lowest \(I_{CC}+I_{CH}\) values, as illustrated in Figure 3b. The incorporation of 20% rubber by weight of the binder in the L15 mix yielded an extracted  
Figure 2: Ensuring no TCE traces in the extracted binders: (a) 3400 to 3000 cm\({}^{-1}\); (b) 1000 to 700 cm\({}^{-1}\). binder with an elevated rutting parameter relative to that of the L5 extracted binder from the identical mix without rubber. This illustrates the impact of rubber on enhancing stiffness, as evidenced by the elevated aging indices in Figure 3a and diminished aromatic and aliphatic indices in Figure 3b. The Pearson correlation and \(p\)-value analysis indicated a strong positive correlation between \(G^{\star}\)/sin\(\delta\) and \(I_{CO}+I_{SO}\) (R = 0.97 and \(p\)-value \(<\) 0.05), suggesting that an increase in oxidative indices significantly increased binder stiffness. As binders became more aged, an increase in oxidative indices correlated with a decrease in aliphatic compounds and an increase in aromatics, leading to a higher \(I_{CO}+I_{SO}\) and a lower \(I_{CC}+I_{CH}\)[12; 52]. Thus, \(G^{\star}\)/sin\(\delta\) exhibits a strong negative correlation with \(I_{CC}+I_{CH}\) (R = \(-\)0.96 and \(p\)-value \(<\) 0.05). R% exhibited a moderate-to-strong positive correlation with \(G^{\star}\)/sin\(\delta\) (R = 0.87 and \(p\)-value \(<\) 0.05), indicating that the thermal residue affects the rheological performance. Figure 4 illustrates the fatigue and block-cracking parameters for the three extracted binders of the field mixes aged 4, 9, and 14 years (F20, F33, and F42). The diameters of the  
Figure 3: Rutting parameters of extracted binders with (**a**) \(I_{CO}+I_{SO}\), (**b**) \(I_{CC}+I_{CH}\), and (**c**) R%. green bubbles indicate \(G^{*}\)sin\(\delta\) values, whereas the diameters of the plum bubbles represent the G-R values. The results of the thermal cracking of the same samples (F20, F33, and F42) are illustrated in Figure 5, indicated by the diameter of the bubbles, which correspond to the \(\Delta T_{c}\) values. The first sample, F20, had 30% ABR from RAP; the second sample, F33, had 16-15% ABR from RAP-RAS, while the third sample contained neither RAP nor RAS.