Experimental study on the polyurethane-bound pervious mixtures in the application of permeable pavements

Abstract Permeable pavements have been widely regarded as an effective way to restore the ecological functionality of urban road systems such as natural infiltration properties. However, pore structures are usually exposed to the air and moisture which accelerate the aging of conventional pavement materials and reduce the durability of the pavement. The development and optimization of polyurethane (PU) binder in recent years, has facilitated excellent performance of polyurethane-bound pervious mixtures (PUPM) by greatly improving the mechanical connection at aggregate-aggregate contact points and thereby effectively extends the service life of permeable pavements. However, due to the different mechanical behavior compared to conventional pavement materials, the primary mechanical behavior and failure process of PUPM are still unclear. This study characterizes the primary mechanical behavior by using modified testing methods and combining standards of concrete and asphalt. The results show outstanding compressive and tensile strength of PUPM due to the excellent adhesion properties between aggregate and PU binder. Different failure characteristics were presented by differently graded PUPM variants, where the ductility can be increased by adjusting the aggregate gradation. Further, functional properties of PUPM variants were also examined and compared with conventional porous asphalt (PA). Both the hydraulic conductivity and acoustic properties of PUPM were observed to be superior to those of PA. Specifically, longer pavement mechanical and functional durability was addressed. This study provides an important reference for the application of PU binder in pervious pavement and the understanding on the pavement functionality of PUPM.