Performance evaluation and microstructural characterization of waterborne epoxy resin–styrene butadiene rubber composite modified emulsified asphalt

To address the insufficient high-temperature performance of conventional styrene butadiene rubber (SBR)-modified emulsified asphalt and its limitied durability as a fog seal binder, this study developed a waterborne epoxy resin–styrene butadiene rubber (WER–SBR) composite modified high-performance emulsified asphalt. Composite samples were prepared with WER contents ranging from 0% to 15% at 3% interwals, and performance was evaluated through tests relevant to fog seal applications, including conventional properties, adhesion performance, rheological characteristics, curing time, and bonding strength. Fluorescence microscopy (FM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were employed to characterize the microstructure and elucidate performance enhancement mechanisms. Results indicate that WER incorporation effectively improves high-temperature stability and interfacial adhesion, while reducing low-temperature crack resistance. Excessive WER content (>9%) leads to pronounced low-temperature brittleness, whereas a recommended dosage range of 6%–9% achieves a favorable balance between high- and low-temperature performance. Microstructural observations show that WER is uniformly dispersed within the SBR matrix and forms a three-dimensional network structure, enhancing mechanical strength through physical blending effects. This study provides key parameters for optimizing high-performance WER–SBR composite modified emulsified asphalt and offers practical guidance for fog seal-based preventive maintenance.