VO2 sprayed cementitious materials for thermochromic building envelopes
Paloma Sirvent, Gloria Pérez, A. Guerrero
Abstract
The research on smart building envelopes is urgently needed to respond the requirements of energy efficient buildings. For that purpose, this paper studies the development of innovative thermochromic cementitious materials based on VO2. The VO2 powder is added on the surface of cement based materials at early hydration stages by spraying an aqueous VO2 dispersion. The spraying was done on cement paste surfaces after different times since the paste compaction (between 0 and 120 min). The suitability of this method has been positively proven by microstructural characterization (X-ray diffraction and scanning electron microscopy analyses) and near infrared reflectance measurements. This has been indicated by the proper integration of the VO2 powder in the cementitious matrix and the structural and chemical stability of the thermochromic VO2(M) phase. The results have also indicated that the optimal time to perform the spraying should be lower than 1 h since the compaction. Moreover, the reflectance modulation of the samples was shown to be maximized with the increasing VO2 concentration at the sample’s surfaces, and it was limited by the reflectance modulation of the powder to a 3.5 %. Finally, preliminary durability tests have proven that the thermochromic properties remain unchanged after exposure to outdoor conditions. These results open a field of research to optimize the thermochromic modulation by controlling the powder properties and concentration to achieve a significant impact of this smart optical behavior on the solar energy management in building envelopes.