Experimental and numerical study on mechanical properties of different bonding layers between ultra-high performance concrete and asphalt surface course

Ultra-High Performance Concrete (UHPC) bridge decks have been extensively adopted in steel bridge engineering owing to their significant advantages, including light weight, high load-bearing capacity, wide applicability, and ease of construction. However, field investigations reveal that distress in composite deck systems often originates in the asphalt layer. This is mainly due to insufficient bonding between the UHPC and asphalt layers, which can result in asphalt overlay issues such as rutting, cracking, and interlayer slippage. In this study, the interfacial mechanical properties of four types of bonding layers in UHPC – asphalt composite structures were investigated through experimental tests and numerical simulations. Oblique shear, direct shear, and pull-off tests were systematically performed to evaluate bonding performance under both ambient (25°C) and elevated (60°C) temperature conditions. Based on the experimental outcomes, the epoxy resin and crushed stone bonding layers were selected for further numerical simulation analysis. The results indicate that the crushed stone bonding layer exhibits excellent shear strength (0.59 MPa at 25°Cand 0.36 MPa at 60°C), whereas the epoxy resin bonding layer (0.46 MPa at 25°C and 0.30 MPa at 60°C) demonstrates superior interfacial load-transfer capacity. The findings of this study offer theoretical support for the design and engineering application of UHPC- asphalt steel bridge deck pavements.