Road performance and chemical evolution of aged asphalt subjected to intense ultraviolet radiation and large temperature fluctuations

Abstract

The primary factors contributing to asphalt pavement deterioration in northwest China are intense ultraviolet (UV) radiation and significant temperature fluctuations, posing challenges for pavement durability. A UV-freeze–thaw coupling aging simulation method tailored to the climate of northwest region were proposed to investigate the degradation mechanisms of asphalt pavements. The conditions were determined that ultraviolet irradiation duration ranged from 24 h to 96 h at 70℃, and the freeze −thaw cycle consisted of 10 h freezing at −18℃ and 14 h thawing at 30℃. Subsequently, the physical, rheological, and road performance characteristics of asphalt and mixtures were then analyzed, followed by chemical analysis and Pearson correlation to explore the aging mechanisms. Results indicated that, coupled aging induced more severe deterioration than individual factors. Physical properties and DSR tests showed ultraviolet caused greater physical degradation than freeze–thaw. The penetration and ductility of the base asphalt decreased by approximately 54 % and 50 % while the SBS-modified asphalt exhibited reductions of 40 % and 20 %, respectively. Rutting, low-temperature beam bending, and freeze–thaw splitting tests revealed that freeze–thaw as primary degradation driver, with UV accelerating aging. The dynamic stability of the base asphalt mixture after freeze −thaw aging decreased by 56.5 %, flexural tensile strength reduced by 20.7 %, and splitting strength ratio declined from 82.7 % to 69.3 %. FTIR, GPC, and Organic elemental analysis revealed that the demonstrated coupled aging altered colloidal structure through aromatic compound cleavage and oxidation. The oxygen content of the two asphalt substrates decreases to 15.33 % and 13.11 %, while SBS-modified asphalt showed a smaller decrease to 7.58 %, confirming SBS’s significant anti-aging enhancement.