The global asphalt production growth rate exceeded 10% in the past decade, and over 90% of the world's road surfaces are generated from asphalt materials. Therefore, the issue of asphalt aging has been widely researched. In this study, the aging of asphalt thin films under various natural conditions was studied to prevent the distortion of indoor simulated aging and to prevent the extraction of asphalt samples from road surfaces from impacting the aged asphalt. The aging of styrene-butadiene-styrene (SBS)-modified asphalt was simulated at four different locations on an asphalt road surface. The aging characteristics of asphalt binders across various structural layers were revealed using Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and linear amplitude scanning (LAS). The results indicate that the aging behavior of the asphalt functional group on the road surface differs from other conditions; the asphalt fatigue life of 4 months equates to the 16-month aging life of asphalt within the dense-graded asphalt road surface. After 8 months of aging, the surface smoothness of the asphalt was significantly compromised. Inside of the porous pavement, the asphalt functional group is more likely to interact with water molecules than inside the dense pavement with cracks, and the variations in roughness and the reduction in fatigue life are also more significant.
Keywords: asphalt natural aging; cracking propagation effects; different locations; fatigue life; outdoor simulation; pavement structure.