Study on the Curing Process of Epoxy Asphalt

In the present study, the curing process of epoxy asphalt was studied using Fourier transform infrared spectroscopy (FTIR) with attenuated total reflectance, fluorescent microscopy morphology, and surface free energy. FTIR was utilized to track the functional group changes in epoxy resin (part A) and asphalt containing a curing agent (part B) at different curing times. It is proposed that the curing agent (hardener) in the asphalt (part B) is a carboxylic acid. The curing process is the reaction between the carboxyl group and the epoxy group through which the ester carbonyl group is formed, whereby carbonyl acid molecules and epoxy molecules are bound together to form a cross-linked network. The fluorescent microscopy morphology analysis indicates that the cross-linked network did not form at the beginning of the reaction. In the cured epoxy asphalt system, the epoxy resin is the continuous phase, and the asphalt constitutes the dispersed phase. The sessile drop method was employed to measure the static contact angle between asphalt binders and three probe liquids. The surface free energies of the epoxy asphalt at different curing times were determined using the Owens–Wendt method. Contact angle and surface free energy measurements indicate that the polarity of epoxy asphalt was reduced and the dispersion part was increased with the extended curing time.