# Anti-Aging Performance and Action Mechanism of Asphalt Modified by Composite Modification
## 3 Results and Discussion
### Scanning Electron Microscope Test Results  
(1) Microscopic morphology and elemental composition of modifier  
Figure 12 presents the microscopic morphology and EDS (Energy Dispersive Spectroscopy) analysis results of the ULDHs modifier, which is a composite of UV absorbers and hydrotalcite (LDHs). As shown in Figure 12, ULDHs contains elements such as O, Mg, Al, N, C, Na, and Zn, with oxygen (O) being the most abundant element at 62.6%. Magnesium (Mg) and aluminum (Al) are the next most prevalent elements, with contents of 19.2% and 10.5%, respectively (about 0.308 and 0.168 times the content of O). Nitrogen (N), carbon (C), zinc (Zn), and sodium (Na) have relatively minor contents, at 5.242%, 1.712%, 0.414%, and 0.184%, respectively. Figure 10: Cumulative strain and cumulative strain difference of matrix asphalt and modified asphalt with different UV aging times. Figure 11: Unrecoverable creep flexibility and the difference of unrecoverable creep flexibility of matrix asphalt and modified asphalt under different UV aging times. Figure 12: Content and distribution of modifier elements. It is noteworthy that the element types in ULDHs are a combination of those found in both LDHs and UV absorbers, with no new elements detected beyond those present in LDHs and UV. This indicates that the composite effect of LDHs and UV does not generate new elements, suggesting that their interaction is primarily a physical blending. Additionally, compared to the UV absorber, ULDHs exhibits a lower Zn content, likely due to the relatively small proportion of UV in the composite, resulting in a reduced relative amount of Zn in ULDHs. The distribution of elements in ULDHs is relatively uniform, with significant concentrations of O, Mg, and Al, while N, C, Na, and Zn are less abundant. (2) LMA  
Figure 13 shows the microscopic morphology of the interface between hydrotalcite (LDHs) and asphalt. At a magnification of 500, the LDHs particles are not aggregated into clumps but are rather evenly dispersed in the asphalt. The LDHs particles do not fully dissolve in the matrix asphalt but are dispersed as a separate phase, being either completely or partially covered by the continuous asphalt phase. Additionally, a distinct boundary line between the LDHs particles and the asphalt is visible, indicating that the adhesion of the asphalt to the LDHs is relatively weak. Upon further magnification of the asphalt-LDHs interface, as shown in Figure 13b-d, it can be observed that the exposed surfaces of the LDHs particles are completely covered and filled by the asphalt. However, the surface of the asphalt remains relatively smooth without noticeable tensile wrinkles, suggesting that the interaction between the LDHs and the asphalt is relatively poor. (3) UMA  
Figure 14 presents the microscopic morphology of the interface between ultraviolet (UV) absorbent and asphalt. At a magnification of 500, it can be observed that the UV particles are either partially or completely covered by the asphalt. The asphalt surface shows tensile wrinkles, indicating that the polar adsorption ability of the asphalt effectively adsorbs the UV particles. At a magnification of 1500, as shown in Figure 14b, the asphalt surface is uneven with numerous tensile wrinkles. The elevated structures (bright regions) represent UV particles, while the depressed structures (darker regions) represent  
Figure 13: LMA microscopic morphology. the asphalt. The UV particles are thoroughly immersed in the asphalt, with the surface exhibiting a blurred morphology. At a magnification of 3000, shown in Figure 14c, it is again observed that the exposed surfaces of the UV particles are completely covered by the asphalt. The interaction between the asphalt and the UV absorbent creates a blurred contact interface, and directional wrinkles are formed perpendicular to the contact interface. These wrinkles correspond to the tensile wrinkles seen in the 500 magnification images.