Synthesis and Evaluation of Polyurethane as Waterproof Adhesion Layer for Steel Bridge Deck

Service life of traditional steel bridge deck pavement is significantly shortened due to the failure of waterproof adhesion. To improve the interlayer bonding performance and extend its service life, polyurethane is proposed as a waterproof adhesion layer (WAL) for a steel bridge deck. This study aims to synthesize polyurethane WAL by free radical solution polymerization under different types and dosages of crosslinking agents as well as the mixing ratio of an acrylic co-blend. Tensile properties, water resistance, glass transition temperatures, thermal stability, and adhesive strength of the polyurethane binder are evaluated. The results demonstrate that polyurethane WAL yields desirable performance by using a hydroxyl molar ratio of 1/3 and an acrylic co-blend of 65%. Specifically, the tensile strength and breaking elongation of polyurethane WAL reach the maximum values of 6.466 MPa and 268.4%, respectively. The water absorption rate of polyurethane WAL is less than 4%. Glass transition temperatures of polyurethane WAL are between -80 °C and 60 °C, respectively. Polyurethane WAL features remarkable high- and low-temperature performance and thermal stability. Finally, adhesion strength between polyurethane WAL and the steel plate reaches up to 5.21 MPa. The outcome of this study facilitates the design and application of polyurethane waterproofing adhesion layers for steel bridge decks.