Effects of thermal-oxidative aging on mechanical behavior and microstructure of epoxy asphalt binder containing different asphalt contents

With the continuous development and multi-scenario application of epoxy asphalt (EA) binder, it is necessary to investigate the environmental aging of EA under temperature-oxygen conditions. To end this, amine epoxy resin (ER) and amine-cured EAs with asphalt contents of 35, 45 %, and 55 % were prepared and then subjected to thermal-oxidative (TO) aging at 60℃, 85℃, and 100 ℃. The mechanical properties and microstructure of ER and EAs during aging were investigated in this research. The results show that the higher the asphalt content, the more pronounced the mass fluctuation of amine-cured EA. For ER and EAs with 35–45 % asphalt content, TO aging decreased tensile strength, storage modulus, hardness, and glass transition temperature, while elongation and (Tanδ)max increased. However, TO aging produced the opposite trend in these parameters of the EA55 binder. After aging, changes were observed in the chemical structure, including C-H bond cleavage and the formation of carbonyl oxides, amides, and sulfoxides. An increase in asphalt content further exacerbated these structural alterations and reduced the activation energy representing sulfoxide oxidation. Degradation of the resin network in amine-cured EA binders can be evidenced by the amide formation, and the scission of the resin-curer link is responsible for these degradations. Besides, the surface of aged EA exhibited varying degrees of pores, cracks, and wrinkles, all related to asphalt oxidation. The polymer degradation of the amine-resin phase competes with the oxidative hardening of the asphalt phase, leading to the EA's different aging behavior. •Aging mechanism of amine-cured EA was analyzed from multiple scales.•The resin phase reduced the oxidation sensitivity of asphalt phase.•The micromorphology of aged EA was attributed to asphalt oxidation.•The competition between resin degradation and asphalt oxidation resulted in different aging behaviors.