## 2 Materials and Methods
### Measurement
#### 3.3.1 Impact of Pre-Cutting Process on the Chemical Composition of Modified Asphal  
For the purpose of comparing the impact of the pre-cutting process as a substitute for high-speed shearing on the chemical composition of SBS-modified asphalt, with conventionally processed SBS-modified asphalt as the control group, FTIR tests were conducted on SBS-modified asphalt prepared using the pre-cutting process, with particle sizes of 18-30 mesh and 30-100 mesh for the SBS, as described in Section 3.2. The results are shown in Figure 17.  
Figure 17: FTIR testing of SBS-modified asphalt prepared via pre-cutting process and conventional process.  
It was observed that the characteristic peak areas of I\({}_{\text{PS}}\), I\({}_{\text{PB}}\), and I\({}_{\text{Ar}}\) were larger in the SBS-modified asphalt prepared using the pre-cutting process. The peak areas of I\({}_{\text{PS}}\) and I\({}_{\text{PB}}\) were especially large, indicating that the pre-cutting process resulted in a higher dispersion concentration of SBS modifier within the asphalt, leading to better uniformity of dispersion. The larger peak area of I\({}_{\text{Ar}}\) suggests that this might have been due to the longer processing time in the conventional method, resulting in a reduction in the aromatic content of the lighter components.  
The characteristic peak parameters were calculated as shown in Figure 18. The feature parameters of the conventionally processed SBS-modified asphalt were consistently the smallest, consistent with the absorbance curve patterns. Upon comparing the progress of the two sets of SBS-modified asphalt samples prepared using the pre-cutting process, it was found that for the SBS pre-cut with a particle size of 30-100 mesh, both I\({}_{\text{PS}}\) and I\({}_{\text{PB}}\) were larger. This suggests that the smaller SBS particle size achieved through pre-cutting facilitated better dispersion within the asphalt, leading to higher concentrations of the detected characteristic peaks. However, for the SBS pre-cut with a particle size of 30-100 mesh, the I\({}_{\text{Ar}}\) was smaller. This was due to the finer particle size of the SBS, which resulted in a larger contact area with the asphalt matrix. As a consequence, during the swelling process, a greater amount of light components was absorbed.  
3.2 Impact of Pre-Cutting as a Replacement for High-Speed Shearing Process on Anti-Aging Performance  
The FTIR test results for the SBS-modified asphalt prepared with the pre-shredding process and the conventional process after PAV aging are shown in Figure 19. It can be observed that after aging, there was a prominent carbonyl peak at 1600 cm\({}^{-1}\) in both SBS-modified asphalts, and the carbonyl peak area in the SBS-modified asphalt prepared via the conventional process was larger.  
Figure 18: FTIR semi-quantitative analysis characteristics. (**a**) I\({}_{\text{PS}}\); (**b**) I\({}_{\text{PB}}\); (**c**) I\({}_{\text{Ar}}\).  
The carbonyl index was calculated as shown in Figure 20. After PAV aging, the SBS-modified asphalt prepared via the conventional process had the highest carbonyl index, indicating the most severe aging. Compared to the conventional preparation process, when SBS was pre-shredded with a particle size of 18-30 mesh, the carbonyl index decreased by approximately 10%, and when the particle size was 30-100 mesh, the carbonyl index decreased by approximately 13%. This suggests that the new process of pre-shredding SBS resulted in improved aging resistance of the modified asphalt.  
For SBS with a particle size of 30-100 mesh, the improvement in aging resistance was more significant. This is because the finer SBS modifier was more evenly dispersed in  
Figure 19: FTIR test chart after PAV aging.  
Figure 20: Carbonyl index after PAV aging.  
the base asphalt matrix, allowing for better heat and stress distribution. This reduced the occurrence of local hotspots and thermal stress, which helped to slow down the aging process.