Aging Trajectory Analysis of Asphalt: Differential Regulation of UV Aging Processes by Anti-Aging Agents with Varied...

In this study, four types of anti-ultraviolet aging agents-layered double hydroxides (LDHs), organic montmorillonite (OMMT), titanium dioxide (TiO₂), and ultraviolet absorber (UV326)-were employed to modify asphalt. The modified asphalt samples underwent Rolling Thin Film Oven Test (RTFOT) and xenon-lamp aging treatments, and we examined the evolution of their physical properties, rheological performance, and chemical composition. A principal component analysis (PCA) model built on representativeness, discriminative power, and non-redundancy reduced the multidimensional data to two principal components, which together captured 87.540% of the total variance. The dynamic principal component trajectories, plotted from the reduced-dimension data for the unaged-short-term-aged-xenon-lamp-aged process, revealed that anti-aging agents sharing the same protection mechanism led to comparable rates of high- and low-temperature performance deterioration during xenon-lamp aging, whereas agents with different mechanisms resulted in distinctly different patterns of performance deterioration. In the critical xenon-lamp aging stage, the neat asphalt exhibited a trajectory vector change of ΔPC1 = 0.92 and ΔPC2 = 1.25, corresponding to an angle of 54°, reflecting a low-temperature degradation. By contrast, the physical shielding agents LDHs and OMMT produced much steeper trajectories with angles of approximately -80°, where ΔPC2 values rose to as high as 3.67 and 2.19 respectively despite modest reductions in overall aging. The reflective agent TiO₂ showed a more moderate angle of 84°, with ΔPC1 and ΔPC2 values of 0.16 and 1.45, indicating a slight retardation of high-temperature performance loss. Notably, the UV absorber UV326 maintained the same trajectory angle of 56° as the neat asphalt but with reduced magnitudes of ΔPC1 = 0.63 and ΔPC2 = 0.94, suggesting a balanced delay in aging without altering its relative progression. This study proposes a novel analytical framework for mechanism-based clustering analysis and the precise selection of anti-aging agents for asphalt.