# Anti-Aging Performance and Action Mechanism of Asphalt Modified by Composite Modification
## 3 Results and Discussion  
### Physical Performance Test Results  
(1) Softening point  
Figure 4 shows the softening points and the increment of softening points for OMA, LMA, and ULMA. From Figure 4a,b, it can be observed that the softening points of all three types of asphalt increase with the degree of UV aging. The order of softening point increment is OMA \(>\) LMA \(>\) ULMA, indicating that the composite effect of LDHs and UV absorber shows better anti-aging performance compared to the single addition of LDHs. The addition of different types of modifiers also impacts the softening point. After the addition of LDHs and ULDHHs, the softening point of asphalt shows a slight increase. Compared to OMA, the softening point of ULMA increased by 1.39%, while LMA's softening point increased by 2.18%. This suggests that LDHs are more effective than ULDHs in increasing the softening point, which is beneficial for enhancing the high-temperature deformation resistance of asphalt. The increase in softening point after UV aging is primarily due to the aging process causing the lighter components of asphalt (such as saturates and aromatics) to transform into heavier components, increasing the density and hardening the asphalt [24]. Additionally, at all aging stages, the softening points of the two modified asphalts are higher than that of the base asphalt. This is attributed to the adsorption and swelling of the large molecules in the modifiers within the asphalt, which makes the asphalt harder and improves its high-temperature performance [25]. The softening point increments of the modified asphalts are less than that of the base asphalt, demonstrating the effectiveness of the modifiers in enhancing the asphalt's anti-aging  
capabilities. This is likely due to the large molecules in the modifiers forming a network structure with the lighter components of the asphalt, thereby inhibiting the progression of aging to some extent. 2 Penetration  
Figure 5 shows the penetration values and penetration ratios for OMA, LMA, and ULMA. From Figure 5a, it is evident that UV aging significantly affects the penetration of asphalt, with the penetration values of all three types of asphalt gradually decreasing with prolonged aging time. This reduction is due to the aging process causing the lighter components of asphalt (such as saturates and aromatics) to transform into heavier components, resulting in the increased density and hardness of the asphalt material [24]. Additionally, at all aging stages, the penetration values of the two modified asphalts are lower than those of the unmodified asphalt. This is likely because LDHs and ULDHs are polymer compounds that, when mixed with asphalt, increase the molecular weight of the asphalt, resulting in higher viscosity and thus lower penetration values. Analyzing Figure 5b, it can be seen that the penetration ratios of the modified asphalts are higher than that of the base asphalt, indicating that the modifiers significantly improve the anti-aging performance of the asphalt. This improvement is likely related to the cross-linking reactions between the modifiers and the lighter components of the asphalt. After the addition of modifiers, the penetration values of the asphalt decreased substantially. Compared to OMA, ULMA's penetration value decreased by about 17.84%, while LMA's penetration value decreased by about 19.80%. The order of the penetration ratios for the three types of asphalt is ULMA > LMA > OMA, with ULMA having a higher penetration ratio than LMA. This suggests that the composite effect of the LDHs and UV absorber is more effective in enhancing the  
Figure 4: Softening point, softening point difference, and softening point increment of matrix asphalt and modified asphalt. anti-aging properties of asphalt compared to the single addition of LDHs to the base asphalt. 3. Ductility  
Figure 6 illustrates the elongation and elongation ratio for OMA, LMA, and ULMA.