Keywords: concrete, phase change materials, PCM
Summary:Thermal enhancement of a building’s envelope can reduce significant part of the energy demand of buildings for heating and/or cooling. Passive storage in building materials and structures enables exploitation of natural heat or cold sources without any need for additional mechanical means. Recent studies use microencapsulated phase change materials (PCM) in concrete. Adding PCMs to concrete is getting the attention of researchers because doing so increases the thermal mass of concretes as well as providing a better homogeneity of indoor temperature distribution by benefiting from solar energy. This is accomplished when such PCMs melt during the day with solar radiation and freezes at nighttime releasing the heat stored during daytime. PCMs are microencapsulated to control their phase change process without interacting with the environment they are embedded in. In the microencapsulation process, PCM -the core material- gets encased in a polymeric shell. The most important challenges for such applications are achieving a robust shell structure that will endure friction during mixing in coarse aggregates of concrete and maintaining the compressive strength of concrete within desired limits. This study has developed a fatty acid based microencapsulated PCM for building material applications. This new smart material was added in fresh concrete mixes to study their effects on thermal and mechanical properties. Thermal enhancement effect was investigated by thermal cycling in a climate chamber, thermostated bath and by IR imaging. The results indicated that the mechanical strength of concrete was kept well within C20 standards, when 10% microencapsulated PCM was added. Scanning Electron Microscopy images from broken concrete specimens revealed that average particle size of microencapsulated PCM was size 950 nm, shells were not damaged and they kept their integrity during mixing (Figure 1). Thermal cycling and images concluded that concrete specimens with microencapsulated PCM can store heat more and also retain heat longer than standard concretes.