Study on shape-stabilised paraffin-ceramsite composites with stable strength as phase change material (PCM) for energy storage

Abstract

The massive energy consumption in construction has been a critical challenge for sustainable development. Incorporating phase change material (PCM) into construction materials is an effective way to improve energy management. In this work, the paraffin with a melting point of ∼ 28 °C and latent heat of ∼ 193 J/g was absorbed into fly ash ceramsites (artificial porous aggregate) under vacuum pressure. The ceramsite had sizes ranging from 7 to 13 mm, within the size range of coarse aggregates in concrete. The main properties of the raw ceramsite, paraffin, and paraffin/ceramsite composite were tested using Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), microscope, leakage testing, mechanical testing, etc. The PCM incorporation ratio was 45.33 wt%. This incorporation value is adequate for PCM composite in concrete to show the significant performance of thermal regulation. The leakage test result shows excellent stability of the PCM carrying in the ceramsites. The PCM-ceramsite composites present intact structures under heating and cooling cycles because of the low-volume expansion of paraffin. Solidified PCM inside the ceramsite particles improve the strength of the composites. Microcharacterization indicates that the connected pores/cracks inside the ceramsite particles are the primary path, while unconnected pores have little benefit for PCM incorporation. Small pores have better PCM retaining efficiency, especially if they are located at the sub-deep layer. Large pores provide ample space for PCM but have adverse effects on to the strength of the PCM-ceramsite composites. Finally, an optimal structure of ceramsites was proposed for PCM.