Cement based-thermal energy storage mortar including blast furnace slag/capric acid shape-stabilized phase change material: Physical, mechanical, thermal properties and solar thermoregulation performance

Solar thermal energy efficiency of cementitious mortar is enhanced by introducing a phase change material (PCM) with thermal energy harvesting/releasing ability. Within this framework, a new type of cement based-thermal energy storage mortar (CBTESM) was developed by substituting blast furnace slag (BFS)/capric acid (CA) shape-stabilized PCM (SSPCM) with 15%, 30% and 45 wt% of sand. The results of XRD indicated that crystalline structure of CA was not affected with addition of BFS. The results of SEM/EDS confirmed successful impregnation of the melted CA into the BFS as carrying material thanks to the capillary forces. DSC analysis indicated that melting temperature and latent heat of fusion for SSPCM is 28.0˚C and 55.5 J/g while they are 28.52˚C and 13.8 J/g for CBTESM containing 45 wt% SSPCM. When 45 wt% SSPCM was added to mortar, bulk density (1.45 g/cm³), compressive strength (8.16 MPa) and thermal conductivity (0.601 W/m.K) decreased by 28.57%, 85.37% and 41.25%, respectively. The CBTESM sample including 15 wt% SSPCM additive (22.51 MPa) can meet the standard conditions in terms of compressive strength. Thermoregulation performance test under actual ambient conditions demonstrated that the developed CBTESM considerably reduced the indoor temperature. Theoretical calculations showed that a 13.5 kWh energy saving can be achieved by using 1 kg CBTESM in a wall having size of 3 × 4 × 0.2 m. Also 36.67, 35.73 and 5.87 kg-CO₂ reduction in carbon emission would be reduced as per 1 kWh coal, natural gas and electricity consumptions, respectively.