Roles of phase change materials on the morphological, physical, rheological and temperature regulating performances of high-viscosity modified asphalt

The composite of phase change material (PCM) and high-viscosity modified asphalt (HVMA) is expected as a new material regulating the temperature of high-performance pavements, thereby ameliorating the urban heat island effect. This study focused on evaluating the roles of two kinds of PCMs, i.e. paraffin/expanded graphite/high-density polyethylene composite material (PHDP) and polyethylene glycol (PEG), on a series of performances of HVMA. Fluorescence microscopy observations, physical rheological properties tests and indoor temperature regulating tests were conducted to determine the morphological, physical, rheological and temperature regulating performances of PHDP/HVMA or PEG/HVMA composites with various PCM contents prepared by fusion blending. Fluorescence microscopy test results revealed that the PHDP and PEG could be uniformly distributed in HVMA, but their distribution size and morphology were obviously different. Physical test results showed an increase in the penetration values of both PHDP/HVMA and PEG/HVMA compared to the HVMA without PCM. Their softening points did not change significantly with increasing PCM content due to the presence of a high-content of polymeric spatial reticulation. Ductility test reflected that the low-temperature properties of PHDP/HVMA were improved. However, the ductility of PEG/HVMA was much reduced due to the presence of large size PEG particles especially at 15 % PEG content. Rheological results from the recovery percent and non-recoverable creep compliance at 64 °C confirmed that the PHDP/HVMA and PEG/HVMA had excellent high-temperature rutting resistance regardless of PCM contents. Notably, the phase angle results reflected that the PHDP/HVMA was more viscous at 5-30 °C and more elastic at 30-60 °C. By contrast, PEG/HVMA was more elastic at the whole temperature range of 5-60 °C. Lastly but not least, compared to HVMA without PCM, the temperature regulating effect was 4 °C during heating of PHDP/HVMA containing 4 % PHDP and PEG/HVMA containing 15 % PEG, and their delay time were 456 s and 1240 s, respectively.