Microevolution of Polymer-Bitumen Phase Interaction in High-Viscosity Modified Bitumen during the Aging of Reactive Oxygen Species

Understandingthe microevolution of HVMB induced by ROSlays a research foundation for its sustainable and long-life application. The objective of this study is to investigate the microevolutionof the bitumen microstructure, polymer phase, and polymer-bitumeninteraction of high-viscosity modified bitumen (HVMB) in reactiveoxygen species (ROS) aging using the Viennese binder aging (VBA) method.First, the VBA system was utilized to age HVMB with different ROSconcentrations. Then, an optical inverse bright-field, dark-field,and fluorescence microscope (OIM) was used to observe the bitumenmicrostructure, its evolution, and polymer structure degradation ofHVMB during ROS aging. Afterward, ImageJ software was applied to quantitativelyassess the bee structure size characteristics of bitumen and the distributioncharacteristics of the polymer. Finally, the differences in the distributionfeatures of bee structures in the polymer zone (PZ) and non-polymerzone (NPZ) were counted to understand the polymer-bitumen interactionduring ROS aging. The results show that the existence of polymersaffects the distribution state of bee structures in bitumen significantly.The area ratio of bee structures and the average area of bee structuresin HVMB both progressively rise with an increase in ROS concentration,although both are much less than those in base bitumen (BB). The destructionof the polymer phase starts from the inside of polymers during ROSaging. As the ROS concentration increases, the polymer degrades fromthe intact network structure to isolated small molecules. Polymer-bitumeninteractions are widespread in HVMB. A large number of bitumen beestructures are also present in the PZ of HVMB. Moreover, the bee structuresconsiderably grow in the PZ as opposed to the NPZ during ROS aging.The clarification of these microstructural characteristics lays thefoundation for a deeper comprehension of the aging mechanism of HVMBinduced by ROS.

Automated summary

The objective of this study is to investigate the microevolution of high-viscosity modified bitumen (HVMB) in reactive oxygen species (ROS) aging. The results show that the presence of polymers significantly affects the distribution of bee structures in bitumen. The destruction of the polymer phase starts from the inside of polymers during ROS aging, and the polymer degrades from the intact network structure to isolated small molecules as the ROS concentration increases. Polymer-bitumen interactions are widespread in HVMB, and a large number of bitumen bee structures are also present in the polymer zone (PZ) of HVMB. The clarification of these microstructural characteristics lays the foundation for a deeper comprehension of the aging mechanism of HVMB induced by ROS.