Eindhoven University of Technology (EUT) researchers revealed that 45 percent of nitrogen oxides on the road can be removed by creating a roadway made with concrete that is blended with titanium dioxide.  

The study was conducted by the EUT in the Netherlands on a 1,000-square-meter repaved road. Jos Brouwers, professor of building materials at the EUT, noted that the air-purifying test in the new pavement proved to be effective in the laboratory, and has now proved to be effective outdoors as well.

When tested outdoors in the town of Hengelo, the pavement blended with titanium dioxide showed a 25 to 45 percent reduction in nitrogen oxide that came in contact with it as opposed to regular concrete. Titanium dioxide is a photocatalytic material that grabs airborne nitrogen oxides and converts it to harmless nitrates with the help of the sun, and it is washed away by the rain. In addition, the mixed material breaks down dirt and algae, so it is sure to stay clean. 

The cost of lacing titanium dioxide into the concrete costs approximately 50 percent more than traditional concrete, but the increase total road-building costs is only 10 percent. 

The idea of adding titanium dioxide to concrete is not a new concept. In 2007, Italian company Italcementi developed a cement that was also laced with titanium dioxide, and could neutralize certain harmful pollutants. It's called TX Active, and when exposed to sunlight or ultraviolet light, the titanium dioxide transforms any nitrogen oxides or sulfur oxides into harmless nitrates or sulfates which can be washed away by rainwater, much like the titanium dioxide mix that EUT researchers are testing in the Netherlands right now.

Researchers at the EUT are still conducting additional testing, but see a lot of advantages to using titanium dioxide-mixed concrete that could help people breathe cleaner air. But despite these advantages, it will take awhile for this project to come into effect due to the time and cost it will take to repave every road.