Development and evaluation of STRC coating for cooling asphalt pavement and mitigating urban heat island effects

To mitigate the negative impacts of urban heat island (UHI) effects on modern cities, this study developed and evaluated a novel cool coating, solar thermal reflective coatings (STRC), for reducing asphalt pavement temperatures. Firstly, the optical properties were characterized using UV-Vis-NIR spectroscopy, and the thermal performance of eight STRC formulations was assessed using a custom-built testing apparatus. Subsequently, the microstructure and elemental composition were examined using scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). Finally, the optimized coating was applied to asphalt concrete, and its long-term performance and stability were confirmed through durability tests, including water immersion test, temperature variation endurance test, and radiation cycle test. The results showed that chromium sesquioxide (Cr2O3), a critical pigment of STRC, exhibited a high near-infrared reflectance of 54.76 % and a lower visible reflectance of 10.22 %. Among the eight STRC formulations, STRC5 demonstrated balanced performance with a visible reflectance of 35.69 % and a near-infrared reflectance of 71.85 %. The microstructure of STRC5 was uniform with minimal surface defects. When STRC5 was applied to asphalt concrete, it achieved significant cooling effects, maintaining a mean temperature of 49.51 degrees C compared to 60.07 degrees C for uncoated samples, resulting in a maximum temperature difference of 10.56 degrees C after 4 h of light exposure. Durability test results confirmed the long-term performance and stability as the coating withstood extreme temperature fluctuations from -20 degrees C to 60 degrees C and 72 h of water immersion. In conclusion, STRC5 demonstrated great potential to effectively cool asphalt pavement and mitigate UHI effects.