Integrated Performance Assessment of Polyurethane-Based Permeable Pavement Composites

Permeable pavements are increasingly adopted to reduce urban runoff and support sustainable stormwater management; however, their long-term performance in cold regions is often limited by the need to maintain both hydraulic conductivity and durability under freeze–thaw cycles and de-icing salt exposure. This study investigates polyurethane (PU)-bound permeable composites based on granite aggregates for paver joint filling, permeable paver production, and monolithic permeable paving. This study provides a combined evaluation of aggregate gradation and PU binder content in relation to hydraulic performance, mechanical resistance, adhesion/cohesion, water absorption, and salt-freeze scaling resistance. Four mixtures were prepared using different combinations of 0/1 and 2/5 mm granite fractions and PU binder contents. The results showed that all mixtures exceeded the target permeability requirement of 2 × 10−5 m/s, while the coarse-only mixture with 3.0% PU binder provided the most balanced performance. This mixture achieved the highest permeability, the highest compressive and splitting tensile strength among the tested mixtures, the lowest water absorption, and the lowest surface scaling after 28 freeze–thaw cycles in 3% NaCl solution. The findings indicate that a coarse aggregate skeleton effectively bonded by the PU can support both rapid drainage and improved resistance to salt-freeze deterioration. However, further field validation under traffic loading, clogging, and long-term environmental exposure would be needed before full-scale application.