Enhancing interlayer bonding in pavements: performance of an innovative waterborne epoxy resin toughened emulsified asphalt and its gravel tack coat

A toughened waterborne epoxy resin (WER-SBR-toughened) emulsified asphalt gravel tack coat was designed in this paper, aiming at the special performance requirements of the bond layer for thin overlays. The interlayer performance of the WER-SBR-toughened gravel tack coat was systematically evaluated through shear tests and pull-off tests, and an orthogonality experiment was utilized to study the impact of the type and dosage, the gravel particle size and gravel dosage on bonding performance. The results showed that the performance of the interlayer of WER-SBR-toughened emulsified asphalt was significantly improved. Its shear and pull-off strengths increased by 122 % and 110 %, respectively, compared to the base emulsified asphalt. Using a gravel tack coat was found to further enhance the interlayer strength of WER-SBR-toughened emulsified asphalt. Shear and pull-off strengths increased by 22 % and 26 %, respectively, compared to the case without gravel. Range and variance analyses of the orthogonal experiment showed that the type of emulsified asphalt had the most significant influence on bonding performance. The optimal mix proportion was determined as an WER-SBR-toughened emulsified asphalt dosage of 1.6 kg/m 2 and a gravel dosage of 1.1 kg/m 2 .