Study on the Time-Dependent Aging Behavior of Bitumen in Cold and Arid Regions

Abstract The complex and variable service environment of bituminous pavements makes the aging behavior of bitumen difficult to predict. This study aims to reveal the aging mechanisms and kinetics of bitumen in the field. Kinetic aging models were developed for different aging modes. To achieve these objectives, the effects of environmental factors on bitumen were systematically characterized at multiple scales. Performance changes during aging were quantified using the complex modulus and carbonyl index. Aging models for bitumen were developed based on chemical reaction kinetics equations. The results indicated that field aging of bitumen was significantly more severe than laboratory-simulated aging. Thermal-oxidative (TO) aging and all-weather (AW) aging followed a two-stage chemical reaction, starting with a rapid initial aging rate and followed by stabilization. In photo-oxidative (PO) aging, the ultraviolet (UV) radiation maintained the aging process in the rapid-reaction stage, with no constant-rate stage observed. The AW aging results indicated that wind, rainfall, and dust attenuated UV exposure, yielding an aging rate intermediate between those of TO and PO aging. The findings provide theoretical support for durability optimization in design and for life-cycle maintenance decision-making.