Preparation, characterization and thermal properties of surface-modified expanded perlite/paraffin as a form-stable phase change composite in concrete.

Energy storage plays an important role in improving the applicability of a wide range of energy systems. Buildings could be considered as a desirable place for this purpose. Incorporating phase change materials (PCMs) as form-stable composites into the building materials has been widely taken into consideration in recent years. However, there are still some shortcomings in applying this technique. In this study, we focused on a surface modification method to prevent leakage of PCM from porous aggregates during heating/cooling cycles. Paraffin (PA) as phase change material was impregnated into the expanded perlite (EP) particles by vacuum impregnation method, and prepared EP/PA composite was coated by a layer of polystyrene. Thermal characterization of obtained composite samples was conducted by DSC and TG analysis. Also, a simple apparatus was prepared to evaluate thermal behavior of a concrete block made by these modified form-stable PCMs during the heating process. Oozing circle method and visual observation for leakage were conducted for surface-modified EP/PA particles and final concrete blocks, respectively. Finally, compressive strength test was applied to evaluate the feasibility of using concretes made by EP/PA composites as structural concrete. The results showed that using polystyrene as a coating material for EP/PA particles was a promising method for PCM leakage prevention. Latent heat value decreased about 18% for surface-modified EP/PA but no leakage trace was observed; also in spite of decreasing in compressive strength up to 40%, it is still in acceptable range for structural purposes. [ABSTRACT FROM AUTHOR]