# Recycling Aged Asphalt Using Hard Asphalt Binder for Hot-Mixing Recycled Asphalt Mixture
## 3 Results and Discussion
### Performance of Hard Asphalt Modified Aged Asphalt
#### 3.1.4 Rheological Properties of Recycled Asphalt Binder  
The creep stiffness (S) and creep rate (m) of asphalt binder samples were measured using the BBR test at \(-12\)\({}^{\circ}\)C. Generally, the larger the S and the lower the m are, the worse the resistance of the asphalt binder to brittle fracturing in low-temperature environments, which is not conducive to the durability of asphalt pavement. It can be seen from Figure 9a,b that the low-temperature crack resistance of HA was worse than that of VA, which was caused by the addition of TLA. In addition, the low-temperature crack resistance of the virgin asphalt significantly deteriorated after aging, and the S value of a 26 h was 3.2 times that of the VA. In addition, when 50% HA was added to the aged asphalt, the low-temperature stability of the recycled asphalt binder was significantly worse than that of the VA after the corresponding aging time. Therefore, the use of HA as a rejuvenator for aged asphalt leads to worse low-temperature stability, and this conclusion suggests that the HA modifier is not recommended for use in cold regions.  
Figure 9c shows that the high-temperature rutting factor of HA was significantly higher than that of VA, especially at 58 \({}^{\circ}\)C and 64 \({}^{\circ}\)C. In addition, with the increase of the VA aging degree, the rutting factor of A26h asphalt binder increased significantly. The rutting resistance factor of A26h asphalt binder was about seven times higher than that of VA. Furthermore, the rutting factor of asphalt binder with different aging degrees was greatly improved after mixing with 50% HA. For example, at 58 \({}^{\circ}\)C, the rutting factor of A26h + HA was about 20% higher than that of A26. The results of Figure 9a show that HA had a significant effect on improving the rutting resistance of aged asphalt binder. Compared to the conventional asphalt binder, TLA has a high asphaltene and ash content, which contribute to a high stiffness of hard asphalt binder produced with TLA, increasing the high-temperature performance of the hard asphalt binder.  
The fatigue factor G*sin8 was used to compare and evaluate the anti-fatigue characteristics of asphalt binder samples; G*-sin8 refers to the energy lost by the asphalt binder under repeated loads. The smaller the G*-sin8, the less energy is lost and the better the fatigue resistance. The fatigue factor test results are shown in Figure 9. Figure 9 shows that the fatigue factors of HA and VA were very close, indicating that they have similar fatigue resistance. In addition, with the increase of aging time, the anti-fatigue performance of virgin asphalt decreased significantly. For example, the fatigue factor of A26h was about 30 times higher than that of VA. The reason is that as the aging time increased, the asphaltene and gum content in the asphalt binder increased, and the saturated and aromatic components decrease, resulting in an increase in the complex modulus and the fatigue factor. In addition, when HA was mixed with aged asphalt, its fatigue factor was slightly higher than that of aged asphalt. For instance, the fatigue factor of A26h + HA was about 10% higher than that of A26h. The above results show that the fatigue performance of aged asphalt decreases with the addition of HA. This is due to the fact that TLA has a relatively large ash content. After the ash particles precipitate, the elasticity and toughness of HA are reduced, which leads to a decrease in fatigue performance. From this point of view, rejuvenating the aging asphalt binder using HA is not preferred for high-traffic pavements.