Laboratory evaluation of poly(ethylene glycol) for cooling of asphalt pavements

Abstract

Poly(ethylene glycol) (PEG) is a latent heat storage material that has potential to regulate the thermal environment within the asphalt pavement via phase-transition process. However, the properties of PEG vary in terms of its average molecular weight. The PEG selection principle is put forward in this study, which is to not only realize satisfactory cooling function but also minimize the adverse effects on asphalt properties. For illustration, the phase change behaviors and thermal stability of PEG were first studied. It is demonstrated that the PEG samples with its average molecular weight within 2000 ~ 20000 (PEG-2 K ~ 20 K) are characterized by suitable phase change temperatures of 41.27 ~ 62.39 °C, fairly great latent heats of 184.8 ~ 211.9 J·g−1 and excellent thermal stability below 300 °C. The larger molecular weight generally corresponds to the higher phase change temperatures, whereas the greatest latent heats occur at PEG-8 K. Despite that, there are marginal differences among the phase change properties of PEG-4 K ~ 8 K. To further select the ideal PEG, tests for asphalt properties were conducted. Results show that based on the negative role of PEG in the high- and low-temperature properties, temperature and stress sensitivities of asphalt binder, it is necessary to encapsulate PEG before use. Therefore, these detrimental roles are required to be considered when selection of PEG. In terms of our selection principle proposed, PEG with a large average molecular weight is usually preferred except PEG-20 K.