Temperature regulation and rheological properties assessment of asphalt binders modified with paraffin/ SiO2 micro-encapsulated phase change materials

Solar energy, as a renewable energy source, can be maximized through phase change materials, thus making it possible to mitigate the urban heat island. The paraffin/ SiO2 micro-encapsulated phase change material (MPCM) with 53.64 degrees C phase transition temperature was synthesized in this paper via in-situ dehydration and conden-sation reaction, and the cooling effect in asphalt binder was investigated by implementing various experiments. The micro characterization results of MPCM show that the SiO2 shell resoundingly encapsulated the paraffin and the average particle size of MPCM was 94.8 nm. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffractometer (XRD) results show that the interaction between MPCM and asphalt binder was a physical blending process. Furthermore, the initial degradation temperature of 240 degrees C means its remarkable thermal stability and confirms the applicability of MPCM to asphalt binders theoretically. It was found that the melting and solidifying enthalpies of MPCM are 110.5 J/g and 108.7 J/g, respectively, from the differential scanning calorimeter (DSC) results, while the maximum melting and solidifying enthalpies of MPCM-modified asphalt binders can be achieved at 13.76 J/g and 11.04 J/g respectively. The MPCM-modified asphalt binders possess a higher specific heat capacity than base asphalt binders, especially at the range of phase transition temperatures (20-60 degrees C), suggesting the predominant thermal regulation effects. The heating rate of modified asphalt binders is reduced at the temperature ranging from 45 to 55 degrees C due to the phase transition of MPCM. Dynamic shear rheometer (DSR) results demonstrate that the rutting resistance of modified asphalt binders was better than the base asphalt binder at low-temperature and low frequency only at the content of 8 % and 10 %. Thus, we concluded that the paraffin/ SiO2 MPCM is applicable for cooling asphalt pavement and the rheological prop-erties of MCPM in asphalt pavement need further research.