Evaluation of cooling effect and pavement performance for thermochromic material modified asphalt mixtures under solar radiation

Abstract

The thermal effect of asphalt pavements on the surrounding environment in summer is of increasing concern since they absorb a great deal of heat from solar radiation and contribute greatly to the urban heat island effect. A novel thermochromic material modified asphalt binder is proposed to modulate pavement temperature by reversibly changing colors and reflectivity to solar radiation in response to temperature variations. In this study, an attempt is extended into the mixture scale. The cooling effect and pavement performance of thermochromic material modified asphalt mixtures are evaluated using a proposed solar radiation simulation test and various mechanical tests. The thermochromic material modification mechanism is revealed from the physical and chemical points of view. It is found that the addition of thermochromic additive to base binders has a significant cooling effect on asphalt pavements in summer. The maximum temperature reduction is observed at the bottom of the top asphalt layer and the top of the middle asphalt layer. Two types of thermochromic additives show positive and negative effects on rutting resistance. Thermochromic material modification has little effect on low-temperature cracking resistance and all thermochromic material modified mixtures exhibit good moisture stability. Preliminary recommendations on the optimum additive type and content of thermochromic material are proposed. The characteristics of coating, dispersion, and intactness of thermochromic additives in base binders significantly affect the pavement performance of asphalt mixtures. The particle size of the thermochromic additive and the chemical composition of shell material are critical to binder modification.