Photocatalytic roads: from lab tests to real scale applications

This paper gives an overview of our research on photocatalytic concrete, which exhibits air purifying properties. Under the action of sunlight, a catalyst present at the surface of the material is activated, enabling degradation of pollutants from the surroundings and transformation to less harmful products. It is a promising technique to reduce a number of air contaminants, especially at sites with a high level of pollution: highly trafficked canyon streets, road tunnels, etc. In addition, the combination with cement offers some synergistic advantages, as the reaction products can be adsorbed at the surface and subsequently washed away by rain. However, the great potential of this emerging technology is hampered by the lack of uniform testing methods at European level to evaluate the photocatalytic activity. Laboratory research is undertaken at BRRC to compare existing methods and draw up recommendations for future standards. Furthermore, translation of lab testing towards results in situ remains critical to demonstrate the effectiveness on larger scale. In this perspective, several trial applications have recently been initiated in Belgium to asses the “real life” behavior. The paper gives a short overview of the photocatalytic principle and the application in concrete, as well as some main results of the laboratory research recognizing the important parameters that come into play. In addition, the implementation efforts of some recent realizations in Belgium will be presented. Already some very promising results towards air purification have been obtained. Nevertheless, further validation, also with modeling, is necessary to extrapolate the findings and enable a judicial implementation of photocatalytic road materials across the globe.