Study on preparation and heat storage performance of paraffin-expanded vermiculite-based phase change concrete

Paraffin-expanded vermiculite (EV) composite PCMs are prepared by using vacuum adsorption method. Paraffin-EV with an adsorption rate of 52 mass% paraffin is selected as phase change aggregate to replace sand in concrete. The chemical structure is characterized by Fourier transform infrared spectrometer (FTIR). The thermal storage performance and thermal reliability of phase change aggregate are characterized by differential scanning calorimeter (DSC) and temperature–time curve. The results show that adsorbing paraffin wax by expanded vermiculite is a physical process. The phase change temperature is 26.1 °C, and the melting enthalpy of the phase change aggregate is 63.7 J g⁻¹. The mass loss rate of phase change aggregate is 3.26% after 200 cooling/heating cycles. The peak temperature of cement hydration for phase change aggregate is 26.6 °C, which is 4.1 °C lower than that of concrete without phase change aggregate. The prepared phase change concrete shows good heat storage/release performance.