Effect of the Degree of Blending on the Performance of Epoxy Component–Modified Recycled Asphalt and Epoxy Component–Modified Recycled Asphalt Mixture

The blending behavior of thermosetting epoxy asphalt in recycled mixtures is significantly different from that of thermoplastic asphalt. Investigations into the degree of blending (DOB) between epoxy asphalt and aged asphalt is of great practical significance for improving the performance and design of recycled asphalt mixtures. In this study, epoxy component–modified recycled asphalt (EA) and mixture (EAM) with two DOBs were designed, including EA-A and EAM-A with full blending, and EA-B and EAM-B with partial blending. A series of performances of EA and EAM were evaluated using rheological, low-temperature and fatigue tests. The DOB mechanism on the performance of EAM was revealed from the microscopic scale. The results show that the addition of the epoxy component enhanced the stiffness and fatigue performance of the EA. The EAM had good cracking resistance and fatigue performance. At 10%–30% epoxy component content, the lower DOB contributed to the fatigue performance of EA-B better than that of EA-A. Meanwhile, the cracking resistance and fatigue performance of EAM-B were better than that of EAM-A. However, the opposite pattern was observed at 40% epoxy component content. The morphology of the interface showed that the epoxy component of EAM-B was concentrated in a certain area of the interface due to the lower DOB, especially with 30% epoxy component content. When 40% epoxy component content, the denser crosslinked network was formed in the EAM-A with higher DOB. Overall, full blending was not required, and 30% epoxy component content was recommended in EAM.