Polyurethane asphalt binder: a promising candidate for steel bridge deck-paving material

To solve the problems of insufficient flexibility and low-temperature cracking resistance of epoxy asphalt binders in steel bridge deck-paving, a segmented linear polyurethane (PU) asphalt binder with thermoplasticity was synthesised via a chain extension reaction between a PU pre-polymer and chain extender in asphalt matrix. Successful synthesis was confirmed through Fourier transform infrared (FT-IR) spectroscopy. A series of tests were conducted to evaluate the properties of PU binders and determine an appropriate formulation. Asphalt binders with high PU contents (30-50%) perform significantly better than the base binder in terms of the high-temperature, low-temperature and mechanical properties. Further, the synthesised PU binder and other frequently used binders, e.g. epoxy and SBS-modified binders, in bridge deck asphalt pavements were compared. Results show that the synthesised PU binder has remarkably better flexibility and low-temperature property, but worse mechanical and high-temperature properties than an epoxy binder. However, the mechanical and high-temperature properties of the synthesised PU binder are substantially better than those of an SBS-modified binder. These results provide useful information for pavement engineers for selecting steel bridge deck-paving materials.