## 3 Results and Discussion
### Asphalt Mixtures Tests Results
The analysis of the dynamic modulus master curves shows that the asphalt mixture with the waste motor oil and SBS (B35/50 & MotorOil & SBS) is softer than that with bio-oil and ground rubber (PG64-22 & cryoMBO). This result can partially explain the very good fatigue performance previously observed for the new asphalt mixture with waste motor oil and SBS. Furthermore, the stiffness of that mixture (B35/50 & MotorOil & SBS) is similar to that of the conventional mixture with B35/50 bitumen, being slightly higher at very low frequencies and high temperatures. Based on these  
Figure 4: Master curves of the shifted dynamic stiffness modulus for the different asphalt mixtures (T\({}_{\rm ref}\) = 21 \({}^{\circ}\)C) studied in this work (the insert represents the quadratic fitting of the shift factors obtained using the Arrhenius time-temperature superposition principle). results, it can be assumed that the asphalt mixture with bio-oil and GTR should perform better at high temperatures, followed by the mixture with waste motor oil and SBS. The high stiffness modulus at high temperatures (or low frequencies) points towards a high rutting resistance of the asphalt mixtures with modified binders, which is in agreement with the results obtained by other authors [38; 39]. Finally, different rutting resistance tests were applied to evaluate the performance of the asphalt mixtures with modified binders, as previously mentioned in Section 2.2.2. In this particular study, the rutting resistance was obtained by measuring the rut depth formed by successive passages of a wheel, at a temperature of 50 \({}^{\circ}\)C. This test ends after 10,000 load cycles. The wheel-tracking slope in air (WTS\({}_{\text{AIR}}\)) is the main result of this test used to rank the rutting resistance performance of asphalt mixtures, which is calculated based on the evolution of the permanent deformation of the asphalt mixture with the number of cycles during the last 5000 load cycles in the wheel-tracking test. The results of this test demonstrated a higher rutting resistance for the asphalt mixture with waste motor oil and SBS (B35/50 & MotorOil & SBS) in comparison to the conventional asphalt mixture (B35/50), as observed from their final rut values (2.4 mm and 5.0 mm, respectively). Moreover, the new asphalt mixture with waste motor oil and SBS exhibited a very low WTS\({}_{\text{AIR}}\) value (0.05 mm/10\({}^{3}\)), which confirms the good rutting resistance performance of this mixture in comparison to the conventional asphalt mixture (WTS\({}_{\text{AIR}}\) value of 0.20 mm/10\({}^{3}\)). The rutting resistance of the asphalt mixture with bio-oil and ground rubber (PG64-22 & cryoMBO), obtained in the previous study [6], was evaluated through the accumulated strain values of the asphalt mixture in a triaxial repeated loading test. The accumulated strain values obtained in that test at 37 \({}^{\circ}\)C and 54 \({}^{\circ}\)C were 0.14% and 1.00%, respectively. When compared to the conventional asphalt mixture (PG64-22), the results obtained for this mixture with bio-binder are exceptionally good at both temperatures, demonstrating its excellent rutting resistance performance. In conclusion, the very high rutting resistance performance of the asphalt mixtures with modified binders, which is not impaired by the low viscosity of the waste motor oil, confirms the conclusions drawn from the dynamic modulus results.