There are many sustainable technologies designers can utilize these days to make a project more Earth- and people-friendly, but smog-eating cement isn’t the most talked-about – until now. The City of Chicago is pioneering the use of a revolutionary type of cement that is capable of eradicating the air around it of pollution, potentially reducing the levels of certain common pollutants by 20 – 70% depending on local conditions and the amount of exposed surface area.
Photocatalytic cement isn’t exactly news – it was developed by the leading Italian cement maker Italcementi for the Vatican in honor of the 2,000th anniversary of the Christian faith. The Seat of the Catholic Church commissioned the construction of a new church to commemorate the event and wanted surface material that would retain its new appearance despite Rome‘s high levels of air pollution.
The cement that Italcementi developed uses titanium oxide that, when exposed to natural sunlight, triggers a chemical reaction that catalyses the decomposition of dirt or grime on the cement’s surface; thus, it is self-cleaning. What further research in Europe uncovered, however, was that this cement possessed pollution reduction properties that not even Italcementi could have foreseen, capable of cleaning up smog in adjacent air – up to 2.5 meters away – by breaking down the nitrogen oxides which are the result of burning fossil fuels.
Naturally, this makes the photocatalytic cement a perfect paving material as it successfully reduces the amount of toxins expelled by vehicles and inhaled by pedestrians. Italy and other areas of Europe have already paved many of their roads with the revolutionary material, but Chicago is reportedly the first city in America to adopt it, laying down a thin, permeable pavement for the bicycle and parking lanes on Blue Island Avenue and Cermak Road.
There might be a few issues associated with this:
1. What is the relative cost of laying down this kind of cement compared to other road surfacing material? In Illinois, I’ve read before that laying asphalt is cheaper in the short term compared to concrete but more expensive in the long term because it has to be replaced more frequently.
2. Some may not like this news because if the cement can help fight pollution, people may pay less attention to the effect of cars.
According to Nguyen, the titanium dioxide on the cement surface absorbs UV light and uses this energy to react with water vapor in the surrounding air.
The result of this reaction is a highly reactive particle known as a hydroxyl radical.
It is these unstable hydroxyl radicals that in turn decompose a host of other compounds in the surrounding air, including nitrous oxide, a harmful greenhouse gas released in car exhaust…
David Leopold, project manager for the Chicago Department of Transportation, did say the photocatalytic cement is more expensive than regular pavement, but the city expects to see considerable improvement in street-level air quality as a result…
Based on pre-installation estimates, “on a windless day up to about eight feet from the pavement’s surface, you can see demonstrated improvements in air quality,” said Leopold. “Coincidentally, that’s about the height of a person on a bike.”
We’ll see what happens if this concrete is used more widely.