Thermal performance and numerical simulation of geopolymer concrete containing different types of thermoregulating materials for passive building applications

Geopolymer concrete (GPC) containing microencapsulated phase change materials (MPCM) were fabricated in order to achieve a high thermal energy storage capacity of an environmental friendly concrete. Different kinds of MPCM were utilized to investigate the influence of the hygroscopic nature, latent heat, and size of microcapsules on the microstructure and thermal properties of GPC. A combination of polar functional groups on the polymer shell and microcapsules with a small size was found to improve the interface bonds between microcapsules and the GPC matrix, how well the MPCM is dispersed in the GPC, and the thermal insulation properties of the GPC. The energy storage capacity of GPC increases at higher concentrations of MPCM and with a higher latent heat of the MPCM. To determine the thermal impact of buildings utilizing GPC containing MPCM, a numerical model was utilized. The model is based on the implicit finite differences method using an energy balance approach and the heat capacity method. In order to improve the model, a new equation was successfully utilized to fit the specific heat capacity of GPC containing MPCM as function of temperature. The numerical model was verified by experimental measurements of the thermal performance of the GPC. The simulated numerical values obtained for GPC containing MPCM were in good agreement with the experimental data. Higher amounts of MPCM and thicker concrete walls reduce the power consumption needed to maintain an indoor temperature of 23 °C. A power reduction of nearly 35% was achieved when utilizing a 75 mm concrete wall containing 5.2 wt.% MPCM. These building materials are therefore promising for improving human comfort and for reducing the energy consumption of buildings.