Preparation And Properties Of Mineral-based Composite Phase Change Materials For Asphalt Pavements

In this paper,mineral-supported PCMs were prepared to construct the temperature-adjusting asphalt pavements,which can relieve the pavements high-temperature diseases and alleviate urban heat islands effectively.Moreover,the temperature-adjusting asphalt pavements can reduce the surface temperature actively,providing a new idea for the cooling pavements and has important significance for adjusting the temperature field of the pavements.First,Diatomite(DI),expanded perlite(EP)and expanded vermiculite(EVM)were selected as the loaded mineral matrix,polyethylene glycol(PEG)and stearic acid(SA)were chosen as the unit phase change materials,form-stable composite phase change materials(CPCMs)were prepared by vacuum impregnation method.The microstructure and chemical structure of CPCMs were characterized by scanning electron microscope(SEM),fourier transformation infrared(FT-IR)and X-ray diffraction(XRD).Thermal properties of the CPCMs were determined by thermogravimetric(TG)and differential scanning calorimeter(DSC).The thermal storage and release tests were conducted to compare the heat storage and release characteristics of the composites.Thermal cycling test was also performed to determine the thermal reliability of form-stable CPCMs.Moreover,a binary eutectic model was established,SA and palmitic acid(PA)eutectic and(SA+PA)/DI were prepared as the verification to expand the scope for PCMs used in pavements.Finally,temperature-adjusting asphalt mixtures were prepared by substituting the fine aggregates with preferred CPCMs.The cooling evaluation and pavement performance of mixtures were tested to determine the efects of form-stable CPCMs.Otherwise,the PEG/EP temperature-adjusting structure layer and conventional asphalt structure layers was used as the lower and upper layer,respectively.The temperature-adjusting test of combined structure was also determined.All the experimental results show that PEG/EP and SA/DI have the best thermal cycling stability.The calculation of the crystallinity shows that some PCMs have lower loading rates but still exhibit larger phase change enthalpy.The phase change temperature of eutectic was measured to be 54.33 ?,which is lower than that of pure unit PCM and is only 0.18 ?different from the theoretical model of 54.51 ?.The binary form-stable CPCM of(SA+PA)/DI has excellent thermal stability and chemical structural stability.The simulated light tests show that the asphalt mixtures with CPCMs have good temperature regulation effects.The upper surface maximum temperature difference of temperature-adjusting asphalt mixture reaches about 7-10 ?,and the bottom surface peak temperature reduces up to 4-6 ?.The average temperature of the combined structure could be reduced to 2.39 ?,which was basically consistent with the 2.27 ? predicted by the thermostat theory model.The pavement performance of temperature-adjusting asphalt mixtures is slightly lower than that of conventional mixtures.However,the PEG/EP temperature-adjusting asphalt mixture has the best pavement performance.