Abstract
The micromorphological changes and the strength formation mechanism of the curing of epoxy asphalt, which is mostly used for steel bridge deck pavements, were investigated. A tensile test was used to analyze the mechanical properties of epoxy asphalt, and Fourier transform infrared spectroscopy (FTIR) was used to determine the change in the epoxy peak area. Laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM) were used to observe two-dimensional and three-dimensional micromorphological changes, respectively, during the curing reaction of epoxy asphalt. The results of the tensile and FTIR tests on epoxy asphalt showed that the tensile strength and epoxy conversion rate both increased with the curing time and exhibited similar trends, indicating that the network formed by the crosslinking and polymerization of epoxy groups causes the increased strength of epoxy asphalt. The curing degree of epoxy asphalt during the curing reaction can be indirectly evaluated from the conversion rate of epoxy groups. The asphalt tended to evenly be dispersed in the continuous phase of the epoxy resin during the formation of the epoxy resin network, and the network structure increased the deformation of the epoxy resin. The epoxy asphalt curing reaction process was classified into three stages based on the degree of curing.
Highlights
Heavy traffic or traffic overloading often leads to various types of distresses in asphalt pavement, such as cracks, rutting, and shoving [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]. 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]
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 isothermal conditions
Summary
Heavy traffic or traffic overloading often leads to various types of distresses in asphalt pavement, such as cracks, rutting, and shoving [1,2,3]. 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]. Morphological changes in the epoxy asphalt during the curing process were tracked under a fluorescence microscope and showed that the asphalt particle diameter increased with the curing time until a stable crosslinked structure formed. There is a lack of quantitative analysis of the formation process of the epoxy resin crosslinked network structure and the relationship between the strength and the micromorphology of epoxy asphalt. In this study, scanning electron microscopy (SEM) was used to observe the formation of the epoxy resin crosslinked network, to track spatial changes in the network microstructure, and to study epoxy asphalt etched off asphalt at different curing times. The evolution of the mechanical properties of epoxy asphalt during the curing process was analyzed to elucidate the mechanism of the strength growth of epoxy asphalt
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