## 2 Materials and Methods
### Measurement
#### 3.2.5 LAS Test  
The stress-strain curves of pre-cut SBS-modified asphalt with different shredded particle sizes were assessed using the LAS test. The results are shown in Figure 14.  
The stress peak values of SBS-modified asphalt prepared by mixing with different shredded particle sizes were smaller than those of the conventional-process asphalt, and the critical strain points and peak width were larger than those of the conventional-process asphalt. This indicates that the pre-cut SBS-modified asphalt had greater ductility and lower stress sensitivity at elevated temperatures, and entered the failure stage later. The experiment showed that when the SBS structure was predominantly granular, the smaller the particle diameter, the smaller the stress peak value and the lower the asphalt hardness. When the SBS structure transitioned from predominantly granular to filamentous with granules, the stress peak value was further reduced, resulting in even lower asphalt hardness. However, as the filament width and particle diameter decreased, the critical strain point further increased, enhanc  
Figure 13: MSCR tests on modified asphalt mixed with different shredded particle sizes. (**a**) Recovery rate, (**b**) Jnr. During the failure stage, a steeper slope of the peak decrease indicates greater brittleness of the specimen and easier damage. The conventional process for SBS-modified asphalt exhibited the steepest peak decrease slope, leading to rapid failure. Although the structure of asphalt prepared with SBS with a particle size of 18-10 mesh was similar to that of the conventional-process asphalt, the slope of the peak decrease was significantly smaller. This implies that when the SBS structure was granular, a smaller particle diameter resulted in reduced brittleness during the failure stage and longer fatigue life. The modified asphalt samples with particle sizes of 30-18 mesh and 100-30 mesh had both filamentous and granular SBS structures. However, the slope of the peak decrease for the 30-18 mesh asphalt was noticeably smaller, indicating that larger filament width and particle diameter led to reduced brittleness during the failure stage. Furthermore, the calculated fatigue life \(\rm{N_{f}}\) values of pre-cut SBS-modified asphalt samples mixed for different mixing times are shown in Figure 15.  
At 5% and 15% strain levels, the Nf values of SBS-modified asphalt samples mixed with different shredded particle sizes were all greater than those of the conventional-process asphalt samples. This indicates that the pre-cut SBS-modified asphalt prepared through mixing exhibited excellent intermediate temperature fatigue performance. Under the 5% strain condition, as the shredded particle size decreased, the fatigue life of the pre-cut SBS-modified asphalt continued to increase. This phenomenon can be attributed to the fact that at low strain levels, the critical failure strain is not reached and the modified asphalt retains its higher ductility, resulting in an extended fatigue life. Under the 15% strain condition, the fatigue life of the pre-cut SBS-modified asphalt first increased and then decreased as the shredded particle size decreased. Among the different shredded particle sizes, the modified asphalt with a shredded particle size of 30-18 mesh had the maximum fatigue life, followed by 18-10 mesh, and the smallest value was observed for 100-30 mesh. This behavior was observed because the 15% strain level was close to the critical failure strain, at which point the three-dimensional network structure strength of a modified asphalt becomes a crucial parameter in determining its fatigue life. The fatigue life of modified asphalt is jointly determined by its ductility and the strength of the three-dimensional network structure. The network structure of the 100-30 mesh asphalt, due to the smaller filament width and particle diameter, had a weaker load-carrying capacity compared to 30-18 mesh, leading to a shorter fatigue life under high strain levels.