Mutual interactions between carbonation and titanium dioxide photoactivity in concrete

The use of building materials modified with photocatalytic components is constantly growing, due to an increased need for efficient purification strategies to improve air quality in industrial and urban areas. Yet, few works are available on the actual behavior of photocatalysts integrated in supporting materials, in this case concrete, and on the alteration of their properties in time. This work focuses on mechanical and durability aspects of TiO2-containing photocatalytic concrete by examining mutual influences between TiO2 and concrete components, and their evolution with the material aging. Experimental tests showed that concrete rheological properties decreased by adding TiO2; mechanical resistance also decreased slightly, in spite of the filler effect expected from the addition of a nanopowder. On the other hand, carbonation decreased the material photocatalytic efficiency compared to the freshly cast specimens: this was ascribed to variations of pore solution chemistry and possible shielding effects produced by calcium carbonate precipitation. (C) 2013 Elsevier Ltd. All rights reserved.