Design of fly ash based core shell composites as heat reflective coatings for sustainable buildings

Abstract

Solar radiation consists of nearly 49 % near-infrared radiation (Thermal region, wavelength = 750–2500 nm). Heat reflective pigments increases the near infrared reflectance of exterior finishes and paints, there by dropping the surface temperatures of roofs and walls, which, in turn, reduces the cooling-energy demand of the building. However, the cost of developed pigments is prohibitive for wider acceptance of NIR reflective pigments. Fly ash is an industrial waste produced in large quantities by coal based power plants. It creates an environmental problem and therefore efforts are on for its safe disposal or to make value added products. In the present work, Flyash based core shell composite particles are prepared using flyash in the core and nano titanium dioxide as the shell. Coating of titanium dioxide over flyash improves its whiteness and renders high reflectivity which is useful for preparation of reflective coatings for building applications. The coatings possess good abrasion and chemical resistance due to flyash which is abrasive and has good chemical resistance. The composite particles were prepared by precipitation of nano titanium dioxide on flyash surface by two techniques: Insitu and Exsitu. The composite particles were characterized by X-ray diffraction, SEM and DRS (Diffused reflectance Spectroscopy) technique.