Study on the micromorphologies and structural evolution in cold-mixed epoxy asphalt

Cold-mixed epoxy asphalt (CMEA) is a high performance paving material that can be constructed and cured at room temperature. It forms thermal and mechanical performances during curing process. In this study, the phase state and structural evolution characteristics of CMEA during curing were evaluated by curing rheological behavior, mechanical properties, and micromorphology. Viscosity tests and dynamic mechanical analyses (DMA) were applied to study the curing rheological behavior, and tensile tests were used to determine the mechanical properties. Moreover, fluorescence microscopy (FM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were implemented to investigate the micromorphological and molecular structure evolution. The results showed that the curing reaction behavior of CMEA was closely related to temperature. The viscosity–time curves of CMEA satisfied the Arrhenius equation above 45 ℃ and followed a linear trend at low temperature. During the curing of CMEA, the toughness increased in three stages: the toughness growth stage, toughness stability stage and toughness decay stage. Furthermore, the presence of asphalt and its solvent weakened the curing reaction of epoxy asphalt. However, increasing the reaction temperature could increase the epoxy group conversion rate. When the curing reaction was complete, a considerable amount of asphalt solvent mixed with the asphalt and was uniformly distributed within the three-dimensional network structure of the epoxy resin. This mixture adversely affected the toughness of the cured CMEA.