Oxidation and polymer degradation characteristics of high viscosity modified asphalts under various aging environments

High viscosity modified asphalt (HVMA) was the core material to build ecological permeable pavement, while it was prone to aging, which limited its applications for urban sustainability. This study focused on the oxidation and polymer degradation characteristics of the high-content styrene-butadiene-styrene modified asphalt, high-viscosity composite particle modified asphalt and high-elastic modified asphalt under the simulated aging environments of thermal oxidation and weather. Gel permeation chromatography results showed that the increase percent of large molecular size percent and the decrease percent of polymer weight could characterize the oxidation degree and polymer degradation degree, respectively. The degrees of oxidation and polymer degradation in all HVMAs increased synchronously with aging, and reached the highest after the weather aging. The polymer molecular distribution of HVMA would become more uniform with aging from the proposed ratio of polymer weight to polymer content. Dynamic shear rheometer tests reflected that there existed the dual effects of coupling and parallelism during aging of HVMA, i.e. the oxidation-induced hardening effect and degradation-induced softening effect. Furthermore, the change percent of rheological indicators was proposed as the net aging degree. Considering the rheological properties of aged HVMA were the coupling results of dual effects, the net aging degree could represent the oxidation dominance degree or polymer degradation dominance degree of HVMA. Due to the differences of dual effects and polymer molecular distribution, various HVMAs showed the totally different net aging degree ranking, depending on the aging states and rheological indicators. Notably, the high-elastic modified asphalt showed the greatest aging resistance at all aging states as a result of its weak dual effects and most uniform polymer molecular distribution.