Lightweight aggregates as carriers for phase change materials

This paper initially reports on development of lightweight aggregates impregnated with phase change material (LWA-PCM), for application in mortars, plasters and other building materials. This is followed by a study into the development and characterisation of prototype cement mortars using the LWA-PCMs. The work has developed methodologies for efficiently impregnating and hosting phase change materials (PCMs) into lightweight aggregates (LWAs), including aerated concrete particles (ACG) and perlite. PCMs can store and release energy within a given temperature range, moderating thermal fluctuations, resulting in the reduction of energy lost in buildings and increasing thermal comfort. Three commercial PCMs, with melting points between 18 °C and 25 °C, were used in this study. Methods, including vacuum impregnation and immersion, and conditions for optimal absorption of the PCMs into ACG, were developed and evaluated experimentally. Different coating materials, to limit leakage of PCMs from the aggregates, were also trialled as part of this study. Compared to immersion, vacuum impregnation resulted in an increased absorption by up to 15.6 % depending on the type and viscosity of the PCMs. The impregnated aggregates were incorporated into cement mortar mixes, at replacement rates between 10% and 50% (by volume). The effects of PCM impregnated particles on both the mechanical and thermal properties of the cement mortars have been evaluated. Increasing the amount of PCM loaded particles decreased both the flexural and compressive strengths of the cement mortars, by up to 38% and 49% respectively. However, the volumetric heat capacity of the materials increased by nearly 60%. This paper presents a new approach for the design of PCM-loaded aggregate particles, with the potential to be incorporated into different construction materials to improve the energy efficiency and resilience of buildings.