Analysis of rheological behavior and anti-aging properties of SBS modified asphalt incorporating UV absorbent and naphthenic oil (NPO)

•Aging resistance of asphalt was evaluated by macro and micro indicators.•Better aging resistance was obtained after composite modification.•Composite modifier could also enhance the low-temperature crack resistance of SBSMA.•The composite modifier was physically blended with SBSMA. This study aimed to comprehensively enhance the antiaging performance of SBS-modified asphalt (SBSMA) and make it available for long-life applications. UV absorbent (UV-531) and naphthenic oil (NPO) were selected to prepare composite modifiers to modify SBSMA, and then a series of aging tests were conducted. The rheological behavior and antiaging performance of the composite-modified asphalt binders were assessed by dynamic shear rheometer (DSR) and bending beam rheological (BBR) instruments. Then, Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) tests were conducted to investigate the influence of aging methods and the modifier on the functional groups and molecular weights of binders. The results indicated that the incorporation of the composite modifier weakened the rutting resistance, and markedly enhanced the cracking resistance of SBSMA. From the rheological point of view, adding the modifier could significantly improve the resistance of SBSMA to thermal-oxygen aging and UV aging under high and low temperatures. In addition, the UV-531/NPO was physically blended with SBSMA. The carbonyl index (CI) and sulfoxide index (SI) results indicated that the modifier can comprehensively improve the aging resistance of SBSMA, and the higher the content, the better the effect. Compared with control SBS, the 1.4# asphalt increased the small molecular size (SMS) by 1.44%∼2.73% and decreased the large molecular size (LMS) by 0.69%∼2.34%, proving that the composite modifier can provide more light components for SBSMA, especially in the case of a low aging degree.