Elia Boonen

Photocatalytic concrete constitutes a promising technique to reduce a number of air contaminants such as NOx and VOC’s, especially at sites with a high level of pollution: highly trafficked canyon streets, road tunnels, urban environment, etc. The use of a double layered concrete (or two lift concrete) provides a durable solution by allowing the insertion of photoactive TiO2 in the top layer of the concrete pavement and recycled concrete aggregates in the bottom layer, without jeopardizing the durability of the pavement. In contact with light, the TiO2 is activated and able to reduce different pollutants in the air. A double layered concrete with photocatalytic materials in the top layer has been constructed in March 2011. This was done in the framework of a broader environmental sustainability project ECO2PROFIT, which deals with reduction of the emission of greenhouse gasses and sustainable production of energy on industrial estates in the frontier area between Flanders and Holland. This paper focuses on the construction of the double layered concrete in Wijnegem and on the influence of different parameters on the photocatalytic efficiency of the pavement.

Photocatalytic concrete constitutes a promising technique to reduce a number of air contaminants such as NO_x and VOC’s, especially at sites with a high level of pollution: highly trafficked canyon streets, road tunnels, the urban environment, etc. Ideally, the photocatalyst, titanium dioxide, is introduced in the top layer of the concrete pavement for best results. In addition, the combination of TiO₂ with cement-based products offers some synergistic advantages, as the reaction products can be adsorbed at the surface and subsequently be washed away by rain. A first application has been studied by the Belgian Road Research Center (BRRC) on the side roads of a main entrance axis in Antwerp with the installation of 10.000 m² of photocatalytic concrete paving blocks. For now however, the translation of laboratory testing towards results in situ remains critical of demonstrating the effectiveness in large scale applications. Moreover, the durability of the air cleaning characteristic with time remains challenging for application in concrete roads. From this perspective, several new trial applications have been initiated in Belgium in recent years to assess the “real life” behavior, including a field site set up in the Leopold II tunnel of Brussels and the construction of new photocatalytic pavements on industrial zones in the cities of Wijnegem and Lier (province of Antwerp). This paper first gives a short overview of the photocatalytic principle applied in concrete, to continue with some main results of the laboratory research recognizing the important parameters that come into play. In addition, some of the methods and results, obtained for the existing application in Antwerp (2005) and during the implementation of the new realizations in Wijnegem and Lier (2010–2012) and in Brussels (2011–2013), will be presented.