Experimental investigation on thermal characterization of PCM-modified hollow blocks for passive thermal regulation in buildings

The high energy consumption in buildings motivates the need for sustainable thermal management techniques, such as Phase Change Materials. By evaluating the possibility of using an organic Phase Change Material, beeswax with a melting range of 34–36 °C, in hollow concrete blocks for the passive control of indoor building temperatures through the absorption and release of energy in the form of heat of fusion. The beeswax is microencapsulated with a linear low-density polyethylene (LLDPE) shell via a coacervation method. The microencapsulated Phase Change Material (MEPCM) is then incorporated into the blocks utilizing a 1:5 cement-to-fine aggregate ratio and a water-to-cement (W/C) ratio of 0.45, replacing 1.5% of the cement by weight. Three additional block groups were designed using 1.5% lime and 1.5% ground granulated blast-furnace slag (GGBS) as alternatives for comparative analysis, which exhibit higher compressive strength than standard blocks. The compressive strength is 3.60 N/mm² for blocks containing the microencapsulated Phase Change Material, compared with 2.76 N/mm² for standard blocks. The blocks containing the microencapsulated Phase Change Material have the lowest water absorption and moisture movement. The blocks containing the microencapsulated Phase Change Material have the lowest thermal conductivity and the highest thermal resistivity compared to the standard blocks. X-ray Diffraction and Scanning Electron Microscopy tests confirmed the integrity of the microencapsulation and hydration processes. The blocks containing the microencapsulated Phase Change Material have been confirmed to be an effective means of storing renewable energy for building temperature control.