Pervious Concrete with Titanium Dioxide as a Photocatalyst Compound for a Greener Road Environment

Final technical report.PDFTech ReportTNW2011-18DTRT07-G-0010EnvironmentAir pollutionHighway engineeringWashingtonTransportation Northwest (Organization)Shen, ShihuiBurton, MariaJobson, BertramHaselbach, LivTransportation Northwest (Organization)United States. Dept. of Transportation. Office of the SecretaryUnited States. Federal Highway AdministrationUniversity Transportation Centers Program (U.S.)NTL-ENERGY AND ENVIRONMENT-Environment ImpactsUS Transportation CollectionWith the rapid development in transportation related activities and the growth of population density in urban and metropolitan area, the United States is now facing significant challenges in controlling air pollution and the associated problems in human health and living environment. The diesel engine vehicle fleet, in particular trucks and buses, have much lower fleet turnover times and therefore integration of newest pollution control technology into the diesel engine fleet is slower that than of passenger cars. A method of removing these pollutants at the street level once they are emitted to the atmosphere is an attractive air quality management device. Similar to plant photosynthesis, photocatalytic compounds such as titanium dioxide (TiO2) particles can be used to trap and absorb organic and inorganic particles in the air, removing (degrading and mineralizing) harmful pollutants such as nitrogen oxides (NOX) and volatile organic compounds (VOC) into CO2, H2O and harmless inorganic compounds in the presence of UV light (sunlight) [1, 2]. TiO2 is one of the most investigated semiconductors in the field of chemical conversion and storage of solar energy given its distinguished properties as [3]: (a) low cost; (b) fast reaction at ambient operating conditions (room temperature, atmospheric pressure); (c) a wide spectrum of organic contaminants can be converted to water and CO2, and (d) no chemical reactants must be used and no side reactions are produced. TiO2 works as a catalyst and does not undergo change; so it can theoretically be used indefinitely [4]. Road infrastructure materials have extensive areas in contact with the air and vehicle exhaust emissions, Therefore, treating the surface of a pavement with TiO2 can be a very promising approach to degrading harmful air pollutants, and improving the quality of the air. However, uses of TiO2 in infrastructure engineering, especially pavement engineering, are still limited because of several technical difficulties. First, direct interaction of TiO2 with UV light is very critical for the photocatalytic effect. This explains why mixing of TiO2 into traditional concrete can only have limited NOx reduction effectiveness. The process was observed to improve after the concrete material was abraded (some cement paste was peeled off and more TiO2 was exposed at the surface) [5, 6]. The durability of the photocatalytic effect becomes another challenge if TiO2 is applied to highly trafficked highways through surface material adhesion. The dynamic tire-pavement interaction under shear and abrasion impact can easily take off the loose coated TiO2 particles at the surface, leaving untreated pavements. Therefore, to maximize the effect of air purification in pavement engineering through the TiO2 photocatalytic reaction, the researchers need to find better (more efficient and reliable) application methods and appropriate substrate materials to adhere TiO2 to, while at the same time ensuring durability of the attached TiO2 under traffic loading and environmental weathering