A novel reflective material coated polyurethane resin-based porous composite paving material for mitigating urban heat island effect

Abstract

Increasing urban temperatures due to the urban heat island effect and global warming have become a significant concern around the world. As urban areas grow, they often replace naturally permeable materials with impermeable ones, contributing to the urban heat island effect, and raising temperatures by 1 to 3°C annually. This study proposes a solution in the form of a novel resin-based composite paving material that is permeable, reflects sunlight, and maintains flexural strength. The composite consists of natural stone aggregate, recycled plastic, recycled rubber, and polyurethane resin. Testing revealed a flexure strength range of 2.46–2.8 MPa suitable for moderate loads. Optimal proportions featured equal volume percentages of stone aggregate, plastic, and rubber at 0.07 g cm−3 of polyurethane resin offering a 27% porosity aiding water drainage. The porosity analysis conducted on the resin-based composite paving sample using X-ray tomography data found a total porosity of 27.14%, indicating the volume of voids present within the material composed of 26.43%, connected porosity and 0.71% isolated porosity. Anti-skid tests confirmed excellent pedestrian safety with pendulum test values above 35 PTV. Coatings such as glass beads, epoxy white paste, and aluminium powder were explored to enhance reflectivity. Aluminium powder-coated pavement achieved the highest Albedo index of 0.096353, 101.7% more reflective than the reference, surpassing glass bead and epoxy white paste coatings. This innovative paving material addresses urban heat island concerns while offering safety and enhanced reflectivity for public walkways.