## 1 Introduction  
Heavy traffic or traffic overloading often leads to various types of distresses in asphalt pavement, such as cracks, rutting, and showing [1; 2; 3]. To reduce asphalt pavement damage and adapt to various traffic and harsh environmental climate conditions, a variety of modified asphalts (e.g., polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate (EVA), and styrene-butadiene-styrene (SBS)) have been used to reduce rutting, shifting, cracking, and pitting on asphalt pavements and increase the pavement service life [4; 5; 6; 7]. Although these polymers are beneficial for improving the high temperature stability, moisture resistance, and fatigue resistance of the asphalt mixture, these polymers do not change the thermoplasticity of the asphalt, and distresses such as rutting and cracking will still occur under high temperature and heavy load conditions [8]. A thermosetting epoxy asphalt is formed by adding epoxy resin and a curing agent to the asphalt. A crosslinking reaction between the epoxy resin and curing agent produces a three-dimensional network structure in the epoxy asphalt. The asphalt is dispersed in this crosslinked network and is constrained by the network structure, changing the thermoplasticity of the asphalt and producing a thermosetting material [9; 10]. Compared with ordinary pavement, the pavement on orthotropic steel bridge decks experiences greater deformation and higher temperatures [11]. Ordinary modified asphalt mixtures have difficulty meeting the pavement requirements of orthotropic steel bridge decks under heavy traffic. Because modifiers (such as SBS, PE, and EVA) do not change the thermoplasticity of the asphalt, flow deformation occurs at high temperatures. Compared with thermoplastic modified asphalt, thermosetting epoxy asphalt has a higher strength and greater high-temperature stability, and it is widely used in orthotropic steel bridge deck paving [12; 13; 14; 15]. [PERSON] et al. [16] evaluated the mechanical response of epoxy asphalt binders through numerical analysis. The results show that lower levels of activation energy increase the degree of hardening and the rate of viscosity development, and the polymerization rate of the epoxy asphalt binders is highly dependent on the temperature under various (non-) isothermal conditions. In addition, [PERSON] et al. [17] also studied the relationship between mechanical properties and heating conditions during the curing reaction of epoxy asphalt binders by establishing models and thermal analysis. The research results show that the strength increase associated with epoxy asphalt binders depends on heating conditions, and the rate of strength increase is faster at high temperatures. [PERSON] et al. [18] prepared epoxy asphalt mixtures with different proportions of epoxy resin. Micomorphological studies on epoxy asphalt showed a phase transformation from a dispersed phase to a continuous phase for epoxy resin contents above 30%. The epoxy resin network that formed significantly increased the tensile strength and softening point of epoxy asphalt. [PERSON] et al. [19] performed dynamic shear rheological tests (DSR) and dynamic mechanical thermal analysis tests (DMTA) to evaluate the rheological properties and thermal stability of epoxy asphalt, base asphalt, and SBS-modified asphalt. The excellent fatigue resistance and high-temperature stability of epoxy asphalt were attributed to a \"two-phase\" network that formed during the curing of epoxy asphalt. The epoxy resin network is the key factor in forming epoxy asphalt and differs fundamentally from other modified asphalt structures. Studying the curing process of epoxy asphalt and the formation of the epoxy network can elucidate the mechanism of strength formation of epoxy asphalt. [PERSON] et al. [20] used Fourier transform infrared spectroscopy (FTIR) to analyze the curing process of epoxy asphalt. The curing rate remained unchanged during the initial curing stage and then decreased after 70 min.