Development of high performance PCM cement composites for passive solar buildings

Solar thermal energy can be stored in passive solar buildings using either sensible heat storage materials or latent heat storage materials. Structural-functional integrated building materials with integrated thermal energy storage can be developed by compositing phase change materials (PCMs) with building materials. In this study, high performance cementitious composites were developed using microencapsulated PCM (MPCM), nanosilica (NS) and carbon fiber (CF). The mechanical properties, microstructure, thermal conductivity and thermal storage capacity of the MPCM cement composites (M-CCs) were studied. The results showed that, compared with cement paste with MPCM only, the mechanical strength of the M-CC increased with increasing NS and CF content. Significant improvement in early age strength of up to 58% was observed. The thermal conductivity of the composites generally decreased with increasing NS content. However, the presence of CF improved the thermal conductivity of the composites by up to 17.8%, from 0.669 to 0.788 W/(mK). The room model test and infrared thermal image analysis both demonstrated that the presence of CF could substantially improve the heat exchange efficiency of the M-CC. It was concluded that the structural and functional benefits of the cementitious composites can be enhanced by the synergetic effects of MPCM, NS and CF.