Analysis on factors affecting the cooling effect of optical shielding in pavement coatings

Inspired by transparent heat-shielding research, three tungsten bronze nanoparticles (i.e., nano-cesium tungsten bronze (Cs0.3WO3), nano-sodium tungsten bronze (Na0.28WO3) and nano-potassium tungsten bronze (K0.26WO3)) with excellent near-infrared light absorption properties were applied for the first time to prepare pavement coatings so as to alleviate the temperature-related damage of pavement and urban heat island effect. X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible–near infrared spectrometer (UV/VIS/NIR), self-made indoor simulated solar radiation apparatus were employed in this research to study the application of nano tungsten bronze into pavement, as well as its benefit. It was found that the solar reflectivity of the coating is between 3.22% and 6.29%, which is very close to that of asphalt binder, which is 5.24%. The coating made of Cs0.3WO3 nanoparticles reduced the temperature most significantly among all specimens, and the combination of theoretical optimal cooling effect was determined. The correlation between the temperature rising value of the specimen coated with the most effective coating and that of the control specimen was established, which provided a basis for predicting the cooling value of the coating. •Nano-tungsten bronze was applied to road engineering field for the first time.•A new test method for cooling effect of pavement coating was designed.•Cooling effect of coating with MxWO3 was studied.•The ranking of factors which affecting the cooling effect was identified.•The combination with the best cooling effect was determined.