Mechanical Behavior and Thermal Oxidative Aging of Anhydride-Cured Epoxy Asphalt with Different Asphalt Contents

Anhydride-cured epoxy asphalt (AC-EA) is an asphalt/resin two-phase system, the properties of which are affected by the asphalt and resin contents. This study aims to investigate the effect of asphalt content on the tensile properties, hardness, dynamic mechanical parameters, chemical components, and microscopic structure of AC-EA through experimental methods. Thermal aging resistance and mechanism of AC-EA with the asphalt content of 25%, 35%, 45%, 55%, and 65% were also investigated. The results show that as the asphalt content increased from 25% to 65%, the tensile strength and hardness of AC-EA binder increased first and then decreased, the elongation decreased, the glass transition temperature ($T_g$ ) rose, and the carbonyl absorption band changed from a single peak to double peak. The absorption bands of aromatic ether and sulfoxide in AC-EA binder overlapped with each other. The carbonyl ester index (CEI) and sulfoxide index (SI) showed a good linear correlation with the asphalt content. Besides, phase inversion occurred in the AC-EA system when the asphalt content was between 45% and 55%. AC-EA binder with an asphalt content less than 45% is a resin-based composite, and that with the asphalt content higher than 45% is an asphalt-based composite. At the thermal aging process, AC-EA binders with asphalt content higher than 45% were more likely to cause significant changes in the tensile parameters, hardness, and modulus than those with asphalt content less than 45%, indicating that the existence of the resin network can reduce the sensitivity of AC-EA to oxidation. After aging, $T_g$ of resin-based composites increased, whereas that of asphalt-based composites decreased. The Fourier transform infrared (FTIR) and scanning electron microscope (SEM) analyses indicated that the AC-EA binder had both postcuring and oxidative degradation during thermal aging. The postcuring was dominant in the resin-based AC-EA composite, whereas the oxidative degradation was dominant in the asphalt-based composite.