## 2 Experimental Design
### Evaluation of Binder  
#### 2.3.1 Superpave Binder Testing  
Assessing the effectiveness of asphalt binders at different stages of their lifespan is crucial for guaranteeing the strength and longevity of road constructions. An extensive examination was conducted using three standardized test methods recommended by the American Association of State Highway and Transportation Officials (AASHTO): the viscosity test (AASHTO T 316) [31], the dynamic shear rheometer (DSR) test (AASHTO T 315) [32], and the bending beam rheometer (BBR) test (AASHTO T 313) [30].  
The Brookfield Rotational Viscometer was used to perform rheological evaluation through a viscosity test. Viscosity measurements were conducted on a standardized 10.5 g sample of each modified binder type using a number 27 spindle. Tests were conducted at two different temperatures, 135 \({}^{\circ}\)C and 180 \({}^{\circ}\)C, in order to encompass a variety of conditions that binders might face. This technique offers crucial insights into the fluidic properties of binders, which are vital for achieving optimal mixing and compaction procedures in construction. This ensures the appropriate workability and consistency of the asphalt mixture.  
The purpose of the DSR test was to measure the viscoelastic properties of the binders in their original state and after undergoing two aging processes: short-term aging (RTFO) and long-term aging (RTFO + PAV). The test was performed at a frequency of 10 radians per second (approximately 1.59 Hz), which is considered optimal for accurately representing the shear-related behaviors of the material in real-world conditions. The complex shear modulus (G*) and phase angle (\(\delta\)) were calculated. The parameter G*/sin \(\delta\) was specifically derived to evaluate the material's ability to withstand rutting, indicating the binder's capacity to resist permanent deformation when subjected to a load. On the other hand, the measurement of G*-sin \(\delta\) at 25 \({}^{\circ}\)C was conducted to assess the likelihood of fatigue cracking, a crucial factor in determining the binder's ability to withstand repeated traffic loading.  
The BBR test aimed to assess the cold temperature performance of the binders by utilizing the residual samples from the RTFO + PAV process. Creep stiffness (S) measurements were conducted on modified binder beams with dimensions of 125 \(\times\) 6.35 \(\times\) 12.7 mm at a temperature of \(-\)12 \({}^{\circ}\)C to replicate cold-weather conditions. A load of 100 g was exerted, and the displacement at the center of the beam was observed for a duration of 60 s. This test is essential for evaluating the binder's response to thermally induced stresses, particularly its vulnerability to cracking, which can have a significant impact on pavement durability in cold climates.  
The tests were performed three times each, and the average of the results was calculated to ensure statistical robustness and reliability. This versatile evaluation methodology facilitated a thorough comprehension of the performance attributes of asphalt binders throughout different stages of their lifespan, establishing a strong basis for forecasting the long-term performance of pavements and guiding the selection of materials and mix design.