Photocatalytic Warm Mix Asphalt laboratory performance testing

The use of titanium dioxide (TiO₂) coating for pavements has received considerable attention in recent years to improve air quality near large metropolitan areas. However, the proper method of applying titanium dioxide to asphalt pavements is still unclear. This study evaluated the benefits of incorporating titanium dioxide in the preparation of Warm-Mix Asphalt (WMA). Two application methods to integrate TiO₂ were evaluated, a water-based titanium dioxide solution applied as a thin coating and using TiO₂ as a modifier to asphalt binder in the preparation of WMA. Based on the results of the experimental program, it was determined that the photocatalytic compound was not effective in degrading NOx in the air stream when used as a modifier to the binder in the preparation of WMA. This could be attributed to the fact that only a small amount of TiO₂ is present at the surface. When used as part of a surface spray coating, TiO₂ was effective in removing NOx pollutants from the air stream with an efficiency ranging from 31 to 55%. The maximum NOx removal efficiency was achieved at a coverage rate of 0.05 l/m2. However, durability of the surface spray coating requires further evaluation. In addition, the increase in flow rate and relative humidity negatively impacted the effectiveness of NOx reduction efficiency. In contrast, the increase in UV light intensity improved the NOx removal efficiency of the surface coating.