Microscale mechanism and key factors of waterborne epoxy resin emulsified asphalt enhancing interlayer bonding performance and shear resistance of bridge deck pavement

Abstract

In this research, samples of emulsified asphalt with varying concentrations of waterborne epoxy resin were prepared to augment the adhesion performance of emulsified asphalt in bonding layers. The bonding efficacy of waterborne epoxy resin emulsified asphalt (WEREA) was evaluated across different temperatures, application rates, and soaking durations. This evaluation simulated interlayer stress conditions using Binder Bond Strength (BBS) tests, 45° oblique shearing tests, and pull-out tests. To analyze the compositional evolution, polymer distribution, and microstructure of WEREA, a series of tests including Fourier Transform Infrared Spectroscopy, fluorescence microscopy, and Scanning Electron Microscopy were conducted. Findings suggest that WEREA significantly improves both bonding strength and shear strength of the bonding layer, exhibiting the least temperature sensitivity compared to unmodified and Styrene-Butadiene Rubber (SBR) modified emulsified asphalts. The optimal concentration of waterborne epoxy resin is identified as 20%, with an application rate of 0.9 kg/m². Upon curing, WEREA forms a cross-linked 'honeycomb' structure within the emulsified asphalt, facilitating the adsorption and anchoring of asphalt and leading to a transition from an asphalt continuous phase to an epoxy-asphalt biphasic structure. This study provides insights into the microscale mechanisms and critical factors underlying the enhanced interlayer bonding performance in bridge deck pavements offered by modified emulsified asphalt.