Ultraviolet Aging Behavior of Asphalt Based on Principal Component Analysis and the Least-Squares Method

To evaluate the significance of macro/microproperties of asphalt in the ultraviolet aging process and use their correlation to judge the residual engineering properties. The A-70 matrix asphalt and styrene-butadiene-styrene copolymer (SBS)-modified asphalt were subjected to ultraviolet aging at different times in a high-pressure ultraviolet mercury lamp environment box in the laboratory. The physical properties and rheological properties of asphalt at different degrees of ultraviolet aging were studied using traditional physical performance tests, dynamic shear rheological tests (DSR), and bending beam rheological tests (BBR). The microscopic analysis was conducted using Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) tests. The significance of asphalt ultraviolet aging performance testing indicators was evaluated based on principal component analysis (PCA). The least-squares method (LSM) was used to eliminate multicollinearity between independent variables, and a predictive model between physical-rheological-microscopic indicators of asphalt ultraviolet aging behavior was established. The results show that the penetration, ductility, creep rate, and roughness of asphalt decrease gradually with the increase of ultraviolet aging degree, while the other aging evaluation indexes increase. The formation of oxygen-containing functional groups of carbonyl and sulfoxide groups and the decrease of surface roughness are the main driving forces to change the rheological parameters of asphalt. Based on the results of PCA, the rutting factor, carbonyl index, and sulfoxide index have the most significant impact on the ultraviolet aging performance of asphalt. In addition, the correlation coefficients between the measured values and predicted values of asphalt aging test indicators all exceed 0.90, indicating that the established least-squares regression model can effectively predict the changes in physical, rheological, and microscopic properties of asphalt during the ultraviolet aging process.