Cohesion Performance of Tack Coat Materials between Polyurethane Mixture and Asphalt Mixture

Abstract

A polyurethane (PU) mixture was used to replace the wearing course of asphalt pavement because of its excellent mechanical properties, which necessitated the selection of suitable interlayer bonding materials between the polyurethane mixture wearing course and the asphalt mixture bottom course. Five types of tack coat materials were designed, including styrene-butadiene-rubber modified emulsified asphalt (SBREA), waterborne epoxy resin modified emulsified asphalt (WEREA), waterborne polyurethane modified emulsified asphalt (WPUEA), polyurethane, and polyurethane-stabilized fine sand (PUFS). Their cohesion performance under elevated temperature, high-temperature immersion, and freeze–thaw conditions was evaluated with tensile tests and shear tests. The results show that PUFS has the best adhesive properties, followed by PU, WPUEA, WEREA, and SBREA. WPUEA offers remarkable high-temperature stability, but is greatly affected by moisture. PU and PUFS exhibit outstanding freeze–thaw resistance, with the residual tensile strength and shear strength remaining above 75%. By incorporating fine sand into the composition, PUFS enhances interfacial friction compared with PU. However, this modification results in a slight reduction in its water stability.