Performance of self-cleaning cool cementitious surface

A strategy to reduce global warming is to increase the reflectance and thermal emittance of the built environment (Akbari, Menon, e Rosenfeld 2008). The urban heat islands usually increase the temperature by more than 10ºC (Santamouris et al. 2001).  A cool roof can reduce the temperature up to 3.3ºC (Synnefa, Santamouris, e Akbari 2007) and improve indoor thermal comfort and reduce energy consumption. A comfortable indoor temperature in the buildings represents a better quality of life for those who cannot afford air conditioning besides reducing the cooling energy, costs and environmental impacts. 
Most horizontal surfaces in cities are constituted by roofs and pavements and even cool when exposed to natural environment, degradation of these surfaces can occur due to factors such as UV radiation, wind and rain, biodeterioration and soiling.   
Cool roofs and cool pavements constitute most of the horizontal surfaces in cities and interfere with the urban climate. The environmental exposure can cause degradation of these surfaces due to factors such as UV radiation, wind and rain, biodeterioration and soiling. Biodeterioration and soiling can be partially controlled by periodical cleaning but this procedure is time consuming, expensive and wastes water and detergents; moreover, roof cleaning is only possible when the surface is accessible and this is not always possible. Therefore, the best solution is a durable self-cleaning cool surface.  
The aim of this research is to develop a durable self-cleaning cool cement-based surface. Three samples of TiO2 (anatase) products (P25, US NANO - IV and Millenium – TiONA) - added to cement pastes for self-cleaning solution - were studied. All the samples were characterized by X-ray Fluorescence Spectroscopy (XRF), while other tests focused on the measurement of the photocatalytic activity of TiO2, using Congo Red dye on white cement paste specimens. 5% and 30% of TiO2 were added, and the paste without addition was used as a reference. The changes after 5h of UV exposure were measured by surface analysis using absorbance measurements with UV-VIS Spectrophotometer, Raman Spectroscopy and Scanning Electron Microscopy, with EDS. The results showed that cement paste with addition of TiO2 degrades the Congo Red dye more than the reference one and degradation is a function of the availability of TiO2 on the surface.