The Green Cheapies

Hello Green Brick Road

Chad W. Lutz
The next time you’re walking down the street, you might want to watch where you step, because a new concrete mix is said to be kind of hungry these days. It’s been called “NOx Nom Nom Nom,” and it’s an experimental road surface researchers are hoping to use to combat air pollutants.

Researchers at the Eindhoven University of Technology in the Netherlands finished conducting an experiment earlier this summer testing a new eco-friendly road surface that just might, literally, save the planet. Prof. Jos Brouwers of Eindhoven’s Department of Architecture, Building, and Planning first reported the findings back in July that has heads turning in the eco-world. It’s what the scientific community is dubbing, “air-purifying concrete,” and it looks to take a significant bite out of air-borne pollutants.

What’s different about this concrete concoction is that it utilizes titanium dioxide as a main component. Titanium dioxide is a photo catalytic material that when exposed to UV light is said to be able to remove nitrogen oxide particles from our air and convert them into harmless nitrate, which is then simply washed away by the rain. Nitrogen oxides are compounds found in automobile exhaust that cause smog and acid rain.

Scientists on the Netherlands busy Castorweg road quartered off a special 1,000 square meter section to test stone molds of the titanium oxide enriched concrete during a resurfacing project last fall. They then quartered off another 1,000 square meter section using normal paving stones and compared results. What they found was promising, to say the least.

After running a series of three air-purity measurements to test for the presence of nitrogen oxide particles, researchers found that readings taken from areas paved with the enriched TiO2 stones indicated 25% - 45% less nitrogen oxide than readings taken from the area where normal stones were used.

Back in 2008, Time Magazine reported a similar experiment run in the Italian municipality of Segrate. There, researchers found that nitrogen oxide levels were reduced by, “as much as 60%.” The new stones are also said to be “self-cleaning” and actually break down algae and dirt as a bi-product of their chemical photosensitivity. The results of the recent tests taken in the Netherlands were the first from an active roadway.

Excited at the prospect of the new data, Brouwers, who has a PhD in Technical Science and is a full-time professor at Eindhoven University, sees potential for the discovery. In his July 2 lecture, where he unveiled the new findings, he hinted at the technology’s possible use in creating more eco-friendly buildings in the near future.

So why haven’t we seen ODOT crews implementing plans to use TiO2 concrete for our own highways and system of roads? One reason could be the cost. Prof. Brouwers calculates that, overall, utilizing the new technology would only be about 10% more than usual in total road-building costs, but the stones themselves are, “50% more expensive,” than normal concrete paving stones. As of 2002, a comparison survey conducted by the Washington State Department of Transportation comparing the average cost incurred to construct a 1.02-mile diamond interchange, showed that to complete just a single lane mile of the project cost anywhere between $1 million and $8.5 million, averaging just under $2.5 million per project.

Even though this new technology is still a long way off from widespread use, it offers American smog champions like Houston, Los Angeles, Sacramento, Dallas, and other murky metropolitan areas hope when it comes to reducing toxic air-borne emissions from our atmosphere, and a greener peace-of-mind for commuters all around the world.