## 3 Lab Testing Protocol
### DSR Testing  
The complex modulus of different scenarios based on temperature variations is shown in Figure 3. As observed, the complex modulus decreases with an increase in temperature. The lowest magnitude of complex modulus is exhibited by the SBS-7% asphalt mixture. The addition of fibers further increases the complex modulus of the mixtures, with BF exhibiting the highest complex modulus. PF closely follows the complex modulus variations of BF, while LF exhibits the lowest complex modulus among the fiber-modified bitumen mixtures. The formation of a spatial network as a result of using fibers, effectively displaces the external loads, thereby creating a bituminous mixtures with higher resistance to permanent deformation.  
The phase angle for bitumen mixtures at different temperature variations is shown in Figure 4. Since fibers are elastic, the addition of fibers to asphalt reduces the portion of viscous part in bitumen, further causing decrease in the phase angle. Therefore, the deformation resistance is further improved under high-temperature conditions. BF has the least sensitivity to phase angle variations with temperature changes and exhibits the least phase angle among other scenarios. PF closely follows the phase angle variation of  
Figure 3: Complex shear modulus for different scenarios.  
Figure 2: Comparison of indirect tensile strength values at different loading rates.  
BF with a slightly higher magnitude. LF shows the highest phase angle among the fiber-modified mixtures. The SBS-7% mixture exhibits the maximum phase angle, showing a larger viscous portion and leading to occurrence of extreme permanent deformation under high-temperature conditions. Both LF and BF perform better than the base scenario with only SBS-7% SBS, which extends the previous research conducted by [PERSON] et al. [36] in terms of separate evaluation of the rutting parameter, phase angle and complex shear modulus.  
The rutting factors of different scenarios based on temperature variations are shown in Figure 5. Rutting factor provides the performance of bituminous mixtures against rutting and is a measure of rutting resistance. Rutting factor decreases with the increase in temperature, leading to higher occurrence of rutting for bituminous mixtures at high temperatures. The addition of fibers significantly increases the G*/Sin* magnitudes, leading to higher resistance to permanent deformation. Basalt fiber exhibits the highest value of G*/Sin* compared to polyester and lignin fibers. Basalt and polyester fibers offer the same performance improvement in some scenarios. However, in the case of lignin fiber, the difference in G*/Sin* is significant due to inadequate absorption of asphalt binder and reduced density of lignin fibers when mixed. Furthermore, basalt fibers increase the viscosity of asphalt binder, leading to better overall high-temperature performance [1]. Fibers increase the rutting resistance in asphalt mixtures by enhancing the crosslinking of hydrocarbon chains in the bitumen. Among the fiber-modified bitumen samples, BF exhibits the highest rutting factor, closely followed by PF, while the least rutting factor is exhibited by LF. Natural fibers, in case of LF, cannot yield the same results as their inorganic counterparts due to weak resistance to moisture, less compatibility between fiber and matrix, insignificant stability and biodegradation [15].  
Figure 4: Phase angle for different scenarios.  
Figure 5: Rutting factor for different scenarios.