Characterization of Roadway Epoxy Asphalt Binder with Different Epoxy Contents

The increasing durability demand on pavements has led to the formulation of requirements for broader applications of epoxy asphalt in roadway pavements to achieve supreme performance. However, for decades, epoxy asphalt has been mainly used on steel bridge deck pavements, and only a few studies have characterized the dosage and properties of the epoxy asphalt specific for road use. In this study, a roadway pavement–oriented epoxy asphalt, referred to as hyperdurability pavement (HDP) epoxy asphalt, was selected, and the effects of its epoxy resin content on its macroproperties and microproperties were investigated, aiming to the determination of the cost-effective epoxy dosage for road use and enrichment of the characterization of roadway epoxy asphalt. Firstly, the mechanical and rheological properties were evaluated by tensile, viscosity, and Marshall tests to determine the cost-effective epoxy content. The microstructural transformations and chemical compositions were then investigated by using fluorescence microscopy and Fourier transform infrared spectroscopy. Subsequently, a comparison between roadway HDP and other common epoxy asphalt types was conducted in terms of material ingredients and mechanical properties. Finally, a correlation analysis was performed between the macroproperties and microproperties. Results suggest that the epoxy resin content substantially influenced the mechanical properties and viscosity of HDP epoxy asphalt and its concrete, and that the cost-effective epoxy content for road use is equal to 30% by weight. Furthermore, the conversion rate of the epoxy resin group typically grows at a lower rate with higher epoxy content, and the cross-linking network of epoxy asphalt was formed at epoxy contents in the range of 30%–40% by weight. Moreover, roadway HDP epoxy resin has higher epoxy and amine values, thus leading to a higher tensile strength and lower elongation rate in the case of the epoxy asphalt compared with other common hot-mixed epoxy asphalt types. Finally, correlation analysis indicates that the strength mechanism of epoxy asphalt is mainly attributed to the densification of the epoxy resin internetwork and the development of the curing action.