Improvement of thermal and optical responses of short-term aged thermochromic asphalt binder by warm-mix asphalt technology

Abstract Thermochromic asphalt materials, due to their dynamically reversible thermal and optical responses in accordance with ambient temperature, have the significant potential in prolonging the lifespan of pavement and improving the urban climatic environment. However, the traditional hot-mix asphalt mixture preparation method with high-temperature conditions can cause damage to durability of thermochromic microcapsules contained in asphalt matrix and hence compromise the temperature regulation functionality of thermochromic asphalt materials. Therefore, the effects of reduced aging temperature by warm-mix asphalt (WMA) technology on properties of short-term aged thermochromic asphalt binder were investigated in this research in terms of rheological property, fluorescent morphology, chemical structure, optical reflectance and temperature regulation effectiveness. In addition, environmental impacts of thermochromic asphalt mixture with warm-mix technology were also discussed. The results indicate that the mixing and compaction temperatures of thermochromic asphalt mixture can be reduced by 16 oC due to WMA technology. The reduced aging temperature by Sasobit can more efficiently maintain the morphology integrity of thermochromic microcapsules, mitigate the outflow of functional core materials and thus improve the optical reflectance of short-term aged thermochromic asphalt binder. When exposed to outdoor solar radiation in hot summer, the asphalt mixture prepared by thermochromic asphalt can achieve a 3 oC decrease in pavement temperature compared with pure asphalt mixture. In addition, the thermochromic asphalt mixture prepared by WMA technology can further reduce the pavement temperature by 2 oC when compared with traditional hot-mix thermochromic asphalt mixture. The reduced pavement surface temperature in hot summer can significantly reduce the amount of convection and irradiation heat from pavement to urban atmosphere, which is of great significance to the improvement of urban microclimate and the sustainable development of city.