## 3 Results and Discussion
#### 3.1.2 Signal Count  
For the purpose of analyzing the effects of F-T cycles on the compression fracture damage, the evolutions between signal count and load level versus time during compression were obtained for the SBS-modified asphalt mixtures with basalt fiber under various F-T cycles. As shown in Figure 7a, the entire loading process and AE signal count can be divided into three stages by combining the intensity of the AE signal count and the load level. At the first stage, during the compression loading with load level below 0.1, there were almost no AE signal counts generated except several AE counts due to the mechanical noise while loading. After entering the second stage, the AE signal started to come alive. A significant increase in the AE signal count began to appear when the load level was between 0.1 and 0.9. The AE signal count values increased as the load level increased. The increasing AE signal count implies that cracks occurred gradually and preliminarily formed at this stage, then, cracks also developed into stable crack growth under continuous compression loading. As the compression loading continued, the AE signal reached the third stage. During this stage, the highest value of the AE signal count occurred, which means that the cracks in the asphalt mixture specimen developed rapidly. The AE signal count increased significantly, which means obvious cracks appeared inside the specimen, eventually losing resistance and causing damage.  
Figure 6: _Cont._  
Figure 6: The AE amplitude and load level versus time during compression at 50 \({}^{\circ}\)C for SBS-modified asphalt mixture with basalt fiber under various freeze-thaw (F-T) cycles. (**a**) 0 F-T cycle; (**b**) 3 F-T cycles; (**c**) 6 F-T cycles; (**d**) 9 F-T cycles; (**e**) 12 F-T cycles; (**f**) 15 F-T cycles; (**g**) 18 F-T cycles; and (**h**) 21 F-T cycles.  
Figure 7: _Cont._  
As for the influences of F-T cycles on the AE signal count of the asphalt mixtures under splitting loading, the variations of the AE signal count and load level showed similar trends for different F-T cycles. However, by comparing the AE signal counts of different F-T cycles, it can be seen that the density of the AE signal count gradually became slightly smaller, and at the same time, the loading time was shortened to a certain degree with increasing F-T cycles. The first stage was gradually shortened, and the third stage was gradually increased. The occurrence of the second stage gradually moved forward. The F-T cycle processing accelerated the damage of the asphalt mixture specimen, i.e., the F-T cycle had a visible adverse influence on the compression strength of SBS-modified asphalt mixture with basalt fiber.  
Splitting Fracture Characterization Analysis of SBS-Modified Asphalt Mixtures with Basalt Fiber under Various F-T Cycles  
In order to characterize the low-temperature performance of asphalt mixture, the splitting test was adopted for the evaluation of the splitting strength of asphalt mixtures under various F-T cycles. A series of SGC asphalt mixture specimens were prepared and processed for 0-21 F-T cycles. At the same time, the AE technology, as a damage detection technology, was also applied to the fracture of asphalt mixtures.  
Figure 7: The AE count and load level versus time during compression at 50 \({}^{\circ}\)C for SBS-modified asphalt mixture with basalt fiber under various F-T cycles. (**a**) 0 F-T cycle; (**b**) 3 F-T cycles; (**c**) 6 F-T cycles; (**d**) 9 F-T cycles; (**e**) 12 F-T cycles; (**f**) 15 F-T cycles; (**g**) 18 F-T cycles; and (**h**) 21 F-T cycles.