Thermal and structural performance of geopolymer concrete containing phase change material encapsulated in expanded clay

•A geopolymer cube from fly ash, ground granulated blast furnace slag and dune sand is produced.•Expanded clay containing phase change materials is integrated to the cube.•The cube is tested for structural and thermal performance.•The PCM containing cube showed improvements in thermal performance compared to reference.•The PCM containing cube lost structural strength compared to reference. In this paper, novel geopolymer-coated expanded clay-phase change material (GP-L-PCM) macrocapsules added to geopolymer concrete (GPC) with volume ratios of 25%, 50%, and 75% for the production of GP-L-PCM slabs are described. The same amounts of lightweight expanded clay aggregate (LECA) were used to develop LECA slabs. The thermal and structural performances of LECA and GP-L-PCM slabs were compared with a reference GPC slab. It was observed that LECA and GP-L-PCM slabs exhibit lower heat transmission, represented by lower maximum surface temperatures (a decrease of 5.6 °C and 8.0 °C on the back surface) than that of GPC slab. Accordingly, the LECA and GP-L-PCM slabs exhibit U-values of 1.6 and 0.9 W/m2K, respectively, with 75% addition of LECA and GP-L-PCM capsules compared to 2 W/m2K for GPC. Substantial decrease in compressive strength was observed in the LECA and GP-L-PCM slabs as compared to GPC for all tested samples.