Abstract
Three kinds of mineral-supported polyethylene glycol (PEG) as form-stable composite phase change materials (CPCMs) were prepared to choose the most suitable CPCMs in asphalt pavements for the problems of asphalt pavements rutting diseases and urban heat islands. The microstructure and chemical structure of CPCMs were characterized by SEM, FT-IR and XRD. Thermal properties of the CPCMs were determined by TG and DSC. The maximum PEG absorption of diatomite (DI), expanded perlite (EP) and expanded vermiculite (EVM) could reach 72%, 67% and 73.6%, respectively. The melting temperatures and latent heat of CPCMs are in the range of 52–55 °C and 100–115 J/g, respectively. The results show that PEG/EP has the best thermal and chemical stability after 100 times of heating-cooling process. Moreover, crystallization fraction results show that PEG/EP has slightly higher latent heats than that of PEG/DI and PEG/EVM. Temperature-adjusting asphalt mixture was prepared by substituting the fine aggregates with PEG/EP CPCMs. The upper surface maximum temperature difference of temperature-adjusting asphalt mixture reaches about 7.0 °C in laboratory, and the surface peak temperature reduces up to 4.3 °C in the field experiment during a typical summer day, indicating a great potential application for regulating pavement temperature field and alleviating the urban heat islands.
Highlights
Asphalt pavements have been widely used and account for approximately 90% of highways, which play an important role in road construction due to the unique advantages[1]
The results show that the thermal storage and release rate of polyethylene glycol (PEG)/DI is lower than that of the other composites, which indicates the best performance for delaying the temperature rising of asphalt pavements
As can be seen from the spectra (Fig. 6a,c and e), the shape and frequency values of all characteristic peaks almost didn’t change after 100 thermal cycle, which demonstrates that no chemical structure was influenced and no reaction happened during thermal cycles
Summary
The CPCMs must be chemically and thermally stable, no or less change in its chemical structure and thermal performance after long-term utility period. As can be seen from the spectra (Fig. 6a,c and e), the shape and frequency values of all characteristic peaks almost didn’t change after 100 thermal cycle, which demonstrates that no chemical structure was influenced and no reaction happened during thermal cycles. As seen from DSC curves (Fig. 6b,d and f ), the melting temperature of PEG/DI, PEG/EP and PEG/EVM changed as −7.90 °C, −0.34 °C and 2.64 °C, while the latent heats value of melting changed by −11.0%, −1.7% and 8.0% after the thermal cycling test, respectively. According to the above analysis and comparison, it can be concluded that the CPCMs of PEG/EP has the best thermal reliability with regard to the change in its phase change temperature and latent heats. The PEG/EP has the best thermal reliability according to the changes in its phase change temperature and latent heats after 100 thermal cycling test. The temperature-adjusting asphalt mixture with PEG/EP could have a great potential application for regulating pavement temperature field and alleviating the urban heat islands
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