Innovative thermochromic asphalt coating: characterisation and thermal performance

Conventional asphalt strongly absorbs the energy from sunlight due to its black colour. The induced high surface temperature on asphalt pavement during summer and fast temperature drop during winter accelerate the rutting and cracking, impairing its long-term durability. Thermochromic materials, substances that can reversibly change their colours in response to temperature, are characterised as high solar reflectance above certain threshold temperature and high absorbance below the threshold temperature. In this paper, innovative thermochromic coatings are designed to modulate the surface temperature of asphalt pavement and potentially improve its durability and safety. The thermal, optical, and chemical properties of the coatings with thermochromic materials were characterised using modulated differential scanning calorimetry, thermogravimetric analysis, UV–Vis–IR spectrophotometry, and Fourier transform infrared spectroscopy, respectively. Besides, production conditions of thermochromic asphalt coatings were also determined to prevent thermal degradation. Finally, the thermal performance of thermochromic asphalt coatings was evaluated by measuring the surface temperature under different weather conditions. Results of measurements under hot weathers found that the surface temperature of thermochromic asphalt coating is lower than that of the conventional asphalt coating with the maximum decrease as high as 6.6°C. This helps to improve its resistance to high temperature-related performance degradation (such as rutting and fatigue). Furthermore, experimental results during cold weathers indicated that the surface temperature of asphalt concrete covered with thermochromic asphalt coating is generally 1°C higher than that of conventional asphalt coating. This means thermochromic asphalt can potentially delay ice formation on the surface of the road than traditional asphalt. Therefore, the incorporation of thermochromic materials into asphalt pavement will potentially help improve the durability, reduce undesirable environmental impacts, and improve the safety of asphalt roads.