Effect of lightweight aggregate gradation on latent heat storage capacity of asphalt mixture for cooling asphalt pavement

Abstract Phase change materials (PCMs) can regulate the temperature of asphalt pavement through latent thermal energy storage. Composite phase change materials using lightweight aggregate as supporting material have been used in asphalt pavement. This work aims at investigating the effect of lightweight aggregate gradation on latent heat storage capacity of asphalt mixture for achieving satisfactory cooling effect. Polyethylene glycol (PEG) was incorporated in three kinds of fly ash ceramsite (FACS) with different particle size ranges (2.36–4.75 mm, 4.75–9.5 mm and 9.5–13.2 mm) to prepare composite PCMs (PEG/FACS) by a vacuum adsorption method. The results of differential scanning calorimeter test showed that the composite PCMs with smaller particle size had larger latent heat. The leakage experiment confirmed that the composite PCMs coated with cement paste (C-PEG/FACS) had good thermal exudation stability. Two kinds of asphalt mixture, AC-13 and SMA-13, were prepared by replacing aggregate with C-PEG/FACS. For AC-13 gradation, the asphalt mixture prepared with C-PEG/FACS (2.36–4.75 mm) presented the best cooling effect and the lowest strength reduction, compared with control asphalt mixture. As for SMA-13 gradation, the asphalt mixture using C-PEG/FACS (4.75–9.5 mm) had the best cooling effect, but the asphalt mixture prepared with C-PEG/FACS (2.36–4.75 mm) presented the lowest strength reduction. The results of the paper indicated that it is necessary to select reasonable lightweight aggregate gradation as PCM-supporting material for different types of asphalt mixture, in order to achieve satisfactory cooling performance and minimize the strength reduction of asphalt mixture.