Paraffin/expanded vermiculite composite phase change material as aggregate for developing lightweight thermal energy storage cement-based composites

In this study, a new paraffin/expanded vermiculite composite phase change material (PCM) was tailor-made as aggregate for developing lightweight thermal energy storage cement-based composites (LW-TESCCs). Vermiculite calcined at 800 °C for 1 h (EVM-800) can be considered as the optimum paraffin supporting matrix candidate, as it has the best expanded microstructure and crystallization. The composite PCM was fabricated at a paraffin-to-EVM-800 weight ratio of 0.6:1.0 by the vacuum impregnation method. The results of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) show that the paraffin can be well vacuum drawn into the expanded interlayer spaces of EVM-800, and that the paraffin and EVM-800 are chemically inert. The differential scanning calorimetry (DSC) results reveal that the composite PCM has an onset melting temperature of 27.0 ± 0.1 °C and latent heat of 77.6 ± 4.3 J/g, and good thermal stability is clearly suggested by the thermogravimetric analysis (TGA) results. Moreover, the LW-TESCCs with bulk densities below 1500 kg/m3 were further developed by incorporating the composite PCM as sand replacement. It is found that the LW-TESCCs have significantly improved thermal resistance performance and well-endowed thermal storage capabilities. Thus, it can be expected that the potential applications of the LW-TESCCs in building envelopes would significantly contribute to reducing indoor air temperature fluctuations and in saving energy.