A Concrete Solution to Pollution?

Italy's major cities are known for their ancient buildings and equally priceless outdoor statues. Sadly, these congested metropolitan areas are also known for their overwhelming motor traffic, as well as the resultant vehicle emissions, smog, and acid rain, adding to that caused by industrial pollution. These airborne pollutants have no respect for historical value, aesthetic beauty, or the incalculable cultural value of preserving these ancient works of architecture and art. (Perhaps more accurately, it is the human polluters who lack these qualities.) As a consequence, ancient artifacts, such as the Roman Colosseum, are being slowly destroyed as the pollutants eaten away at the vulnerable stone that comprises these treasures — making the material porous, and thus further exposing it to deterioration. In the meantime, the nearby modern buildings, made mostly of concrete, look on impassively as their older counterparts are aged far too quickly.

But what if those modern buildings, or at least their exteriors, could help to protect their threatened ancestors? What if the cement used to make those bare exteriors, or the paint and plaster used to cover their outside surfaces, could somehow neutralize some of those airborne pollutants? That is the idea behind TX Active, a technology that has been in development since the middle half of the 1990s, and is now being deployed by manufacturers of cement in Italy, the world's fifth-largest producer.

The key to the solution is a natural process known as photocatalysis, which, in the presence of light, breaks down carbon monoxide, nitrogen oxide, benzene, and other pollutants. It achieves this by dramatically speeding up the oxidation that converts those substances into less harmful compounds, such as water, carbon dioxide, and nitrates. The photocatalyzer TX Active was developed by researchers at Italcementi Group. It is essentially a blend of titanium dioxide, and can be incorporated into paint, plaster, and mortar, as well as cement. In turn, the compound can be used almost anywhere in an urban environment, including repainting walls, plastering new and older homes, and repaving streets when needed.

What makes this new technology appear to be so environmentally promising, is the tremendous results obtained so far. For instance, in the town of Segrate, near Milan, there is a heavily trafficked street that serves over 1000 cars every hour. Repaving it with material containing TX Active caused a reduction in nitric oxides of approximately 60 percent. As a more extensive test, an industrial area larger than 8000 square meters, located near Bergamo, also received the TX Active treatment, and saw a decrease of 45 percent. Perhaps most remarkable of all, is the estimate (from several sources) that if 15 percent of all visible urban surfaces were covered with materials containing TX Active, then airborne pollution could be reduced by up to 50 percent, depending upon the atmospheric conditions.

As with so many ecological countermeasures, building materials enhanced with TX Active cost more than the standard ones. For example, photocatalytic paving blocks cost approximately one third more than the conventional ones. But that is simply a short-term expense, and greatly outweighed by the long-term benefits. The photocatalytic paint has even less of a premium, adding about 100 euros to the cost of all the paint needed to cover a typical five-story building. These cost differences may actually be less than the money saved from long-term cleaning expenses, since the TX Active materials prevent the pollutants from building up on surfaces.

So when in Rome, do as the Romans do, and say "Ciao!" to "cemento mangiasmog" ("smog-eating cement") — a new technology that could help conquer air pollution and help preserve the stone buildings and statues built in an era when the air was naturally clean.