Rheological Properties and Microstructure of Waterborne Epoxy Resin Modified Emulsified Asphalt

As a road repair material, emulsified asphalt offers advantages such as convenient construction, good fluidity, and environmental safety. However, its relatively low strength limits its application range, making performance enhancement a key research focus. In this study, waterborne epoxy resin (WER) was used to modify emulsified asphalt, and the preparation process and performance were systematically investigated. Three types of waterborne epoxy systems were selected, and through compatibility, film-forming performance, and bonding strength tests, the JT waterborne epoxy system was identified as having the best overall performance, with an optimal epoxy-to-curing-agent ratio of 1:0.6. Modified emulsified asphalts with different proportions of WER and styrene–butadiene rubber were prepared. Using fluorescence microscopy, image recognition techniques, and multiple experimental evaluations, the distribution of epoxy resin in the emulsified asphalt was quantitatively analyzed. The results show that the addition of WER significantly improves the bonding strength of emulsified asphalt, with the fastest rate of increase observed in the 5−10% range. However, a comprehensive evaluation considering microstructure uniformity, rheological performance, and water resistance indicates that the optimal overall performance is achieved in the 10−12% range, and the WER content should strictly be controlled below 15% to avoid severe local agglomeration. Meanwhile, the modified water-boiling test reveals that the adhesion between WERAE and aggregates is significantly enhanced, implying a potentially improved resistance to moisture-induced damage under practical service conditions. The standard deviation of area results indicate that when the WER content exceeds 15%, local agglomeration occurs, which is unfavorable for strength development of the modified system; the distribution uniformity results further show that when the WER content is greater than 12%, it negatively affects the uniform dispersion of WER within the emulsified asphalt.