Performance analysis of paraffin microcapsules and phase change concrete based on microporous cenospheres

Abstract

Combining concrete and phase change materials has created a novel method for building energy conservation. However, introducing phase change materials into the concrete will cause various impacts on its performance. This study explores a novel approach to enhance thermal energy storage in building materials by incorporating phase change materials (PCMs) into concrete. Microporous cenospheres were extracted from fly ash through a three-step process and used to produce composite PCM microcapsules containing paraffin as the core material. The produced PCM microcapsules were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and phase change cycle analysis. Phase change concrete was then formulated by substituting 0–25 % sand with these microcapsules. Effects of the addition of the PCM microcapsule on both the mechanical and thermal properties of concrete were experimentally examined. While the incorporation of microcapsules significantly improved concrete's thermal properties, it also led to a reduction in compressive strength (up to 19.65 % at 28 days), though still meeting specifications. The introduction of microcapsules notably enhanced the temperature control capabilities of concrete. In spring, the model room made with the phase change concrete exhibited a 2.2 °C lower indoor peak temperature 2 h 40 min later than the one room with the ordinary concrete. During active heating in winter, the phase change concrete demonstrated significantly lower indoor temperature fluctuations, with a maximum reduction of 45.39 %. Furthermore, the study found that the particle size of microcapsules had varying effects on concrete performance, with larger particles improving thermal properties and smaller particles enhancing mechanical properties. Overall, this research highlights the potential of composite phase change microcapsules and phase change concrete based on microporous cenospheres for effective temperature control and energy conservation in building applications.