Assessment of impregnating phase change materials into lightweight aggregates for development of thermal energy storage aggregate composites

Abstract

This study assesses the feasibility of the impregnation/encasement of phase change materials (PCM) into lightweight aggregates (LWAs) for engineering applications. Four types of plant-based PCMs (PCM1 – unrefined palm oil, PCM2 – unrefined shea butter, PCM3 – unrefined coconut oil, and PCM4 – Crodatherm PCM) are investigated at material level. Similarly, two types of LWAs are used in the investigations, namely, fly–ash aggregates (FA) and glass aggregates (GA). The aggregates are by-products of the fly-ash and glass wastes generated from the construction and demolition activities. The wastes generated are recycled into various forms to reduce/eliminate the need for landfill disposal, thereby, lowering carbon-based emissions, and minimise resource extraction activities within the construction sector. In the initial investigations of this study, PCM4 was found to be the most energy efficient of all the PCMs. PCM4 had a thermal energy storage value of 33.5 kJ/kg per pound sterling (£) in comparison to 21.43 kJ/kg/£, 27.6 kJ/kg/£ and 20.71 kJ/kg/£ for PCM1, PCM2 and PCM3, respectively. PCM4 was adopted and used for impregnation into the pulverised FA and GA LWAs. Maximum absorption capacities of about 18.56% and 30.66% for the FAs and GAs were observed via vacuum impregnation technique in comparison to 5.78% and 12.86% measured using simple immersion method for the FAs and GAs, respectively. To prevent leakage and avoid coalescing of the aggregates, the PCM impregnated LWAs were coated, first, with primer epoxy resin, followed by graphite powder. Two layers of coating were applied to arrive at a durable product that can withstand abrasive forces (abrasive value of 6 and 21% for the double and single coating), heating and cooling temperatures, salt attack and a combination of thermal load and salt attack that are expected during buildings’ construction or infrastructural development in the industry.