Environmental Effectiveness of Photocatalytic Asphalt Pavement Surfaces Incorporating Ultrafine/Nano Titanium Dioxide

In spite of the importance of the national transportation network, there is a growing recognition that highway operations have major environmental impacts during construction and service. High traffic volumes cause high concentration of nitrogen oxides and volatile organic compounds (VOCs) in the air, which have been linked with serious health hazards to the public. These pollutants may also travel long distances to produce secondary pollutants such as acid rain or ozone. Photocatalysis compounds such as titanium dioxide (TiO2) can trap and degrade organic and inorganic particles in the air removing harmful air pollutants such as NOx and VOC in the presence of UV light. Current research and applications of this technology are limited to concrete pavement surfaces, which only represent 6% of the national road network. About 94% of the road network in the US is surfaced with hot-mix asphalt, which supports directing future research towards the use of titanium dioxide coating in flexible pavements. To address the aforementioned problem, this research project will investigate the possibility of integrating titanium dioxide on the surface of asphalt pavements to develop a photocatalytic asphalt pavement capable of oxidizing traffic pollutants. The photocatalytic properties of TiO2 asphalt pavement as well as its environmental properties will be characterized using a novel environmental laboratory setup. The proposed research is cutting edge and has not been attempted in the US. A recent study attempted to apply the photocatalytic compound as part of a water-based emulsion in Italy. The mixing of TiO2 with an asphalt binder at a 6% content of the binder weight was also attempted in China and was used in the construction of an open-graded friction course.