Light transmitting glass fiber reinforced cementitious composite containing microencapsulated phase change material for thermal energy saving

Abstract: The energy utilization for artificial lighting, cooling, heating, and air conditioning in buildings results in the release of greenhouse gases and causes climate crises. In this regard, a novel light-transmitting cementitious composite (LTCC) was developed by substituting microencapsulated phase change material (MPCM) to reduce the building energy utilization via transmitted light through the composite and improve the solar thermal energy efficiency. The cementitious matrix is produced with cement, kaolin, silica sand, water, superplasticizer, adhesive polymer, glass fiber, different ratios of MPCM, and plastic optical grids to let inward sunlight transmittance. The current study thoroughly investigates the characteristics of light-transmitting composite, including MPCMs, via physico-mechanical, chemical, microstructural, thermal, light transmittance and solar thermoregulation tests. The thermal conductivity of the composite with 0 wt% MPCM decreased from 1.09 W/mK to 0.96 W/mK with 15 wt% MPCM addition. Incorporating 10 wt% of MPCM reduced the 28 days-compressive strength of specimens by almost 28 % due to the lower strength and density of microcapsules, as well as the voids formed by damaged MPCMs. On the other hand, the incorporation of MPCM did not dramatically affect the flexural strength of the cementitious composite. DSC analysis results revealed that the composite containing 15 wt% MPCM shows a latent heat of fusion of 14.6 J/g with a melting point of 17.65 °C. FTIR analysis disclosed that MPCM maintains its chemical structure in the composite. Composite slabs exhibited up to 12.4 % artificial light transmittance, which would translate to a considerable increase in the lighting efficiency of commercial and residential buildings. Thermoregulation performance test under ambient conditions indicates that the specimen containing 15 wt% MPCM can provide a cooler room temperature for 6.5 h when the room or surface temperatures increase above 21–23 °C, and a warmer room when the temperature decreases below these temperatures. The findings of the current study can be applied to enhance thermal energy saving and artificial lighting efficiency in buildings that inspire the design of environment-friendly constructions.

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