The Effectiveness of Liquid PUD-TiO₂ Photocatalyst on Asphalt Pavement

Harmful nitrogen oxides (NO_X) are produced by vehicles, factories, mines, and power plants. In fact, over one million tons of NO_X are emitted into the atmosphere every year, making it the most prevalent air pollutant. Approximately 45% of the emitted NO_X in Korea is associated with the transportation sector. In this paper, the application of a new TiO₂ photocatalyst on the asphalt roads to remove combustion-produced NO_X was studied. In an effort to overcome the known constructability, adhesion, cost, and dispersion problems associated with TiO₂ photocatalysts, the liquid polyurethane (PUD) was added with TiO₂ to form a mixture later known as liquid PUD-TiO₂. Laboratory and field tests were conducted to determine the optimum amount of photocatalyst to be used and the performance of asphalt pavement coated with PUD-TiO₂ in terms of indirect tensile strength, water susceptibility, and rutting resistance. Additionally, the performance of PUD-TiO₂ under different humidity, wind speed, and temperature conditions was also evaluated. The results showed that the application of PUD-TiO₂ photocatalyst on the asphalt pavements road reduces the NO_X available on the surface of the road. The PUD-TiO₂ also was found to have no effects on the performance of asphalt pavement. Meanwhile, under different weather conditions, the reaction between the photocatalyst and NO_X is mainly affected by the humidity.