## 4 Conclusions  
To clarify the effect of F-T conditions on compressive and tensile fracture failure characteristics, variations in compressive as well as tensile strength, and AE signal's direct and indirect parameters were investigated based on the compressive and tensile tests and AE tests of SMA-13. Meanwhile, the effect of F-T condition on the internal void characteristics for bitumen was studied from a mesoscale, and meso-void characteristics were compared.  
1. As the F-T condition continues, uniaxial compressive strength and tensile strength gradually decrease. When F-T cycles reached 21, the loss rate of the high-temperature uniaxial compressive strength at 50 \({}^{\circ}\)C for bitumen incorporating basalt fiber was 24.05%, and the tensile strength decreased by 31.56%, with the most serious loss. The F-T condition had a significant influence on asphalt pavement.
2. Under the action of compression and tensile load modes, the fracture failure process can be divided into four stages combined with signal index as well as loading level. In the loading pre-treatment, smaller values of amplitude and count are observed, which could be regarded as the micro-crack initiation stage. Then, the first and second inflection points occur in the load level, and the AE signal values of amplitude and count change obviously, which are called the micro-crack accumulation stage and damage development stage. Finally, the load level gradually becomes gentle, and obvious macroscopic cracks appear.
3. The time history of the AE signal values of amplitude and count shows stage features of fracture failure procedure for bitumen. According to the AE indirect index, fracture mode variation under compressive and tensile loading is related to failure, showing that the coupling interactions between tensile and shear cracks has a catalytic influence. AE technology could be used to characterize the performance change of asphalt mixtures.
4. Asphalt mixtures have different behaviours for the compressive and tensile strength and fracture failure characteristics based on AE when exposed to F-T conditions, which is attributed to different internal void topologies. During F-T conditions, new voids and cracks formed rapidly, and voids as well as cracks opened gradually.  
This study reflected the fracture failure mode of asphalt mixture based on AE technology for asphalt pavement in seasonal frozen areas. The mechanical properties and fracture characteristics of asphalt mixture in the F-T condition were also revealed. Through this study, the performance deterioration law of asphalt pavement could be grasped in advance and used for the maintenance of asphalt pavement in seasonal freezing areas to achieve sustainable economic development. Due to the limits of the type and loading mode of asphalt mixture, the quantitative prediction of the performance of asphalt mixture using AE signal parameters and CT volume characteristics will be investigated in the future.  
Conceptualization, W.W.; Methodology, W.W. and J.L.; Validation, J.L.; Formal Analysis, W.X. and J.L.; Investigation, W.X. and J.L.; Writing--Original Draft Preparation, W.W.; Writing--Review and Editing, W.X. and J.L.; Project Administration, W.W.; Funding Acquisition, W.W. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Scientific and Technological Project of Science and Technology Department of Jilin Province (grant number: 20210508028 RQ), National Natural Science Foundation of China (grant number: 52208438), Scientific Research Project of Department of Education of Jilin Province (grant number: JJKH20221019 KJ)), China Postdoctoral Science Foundation (grant number: 2021T140262), Key Project of Department of Transportation of Heilongjiang Province (grant number: 2022-1, 2022-2).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.