Situated on the outskirts of Rome, Italy, in Tor Tre Teste, architect Richard Meier’s Jubilee Church anchors a middle-income housing project built in the 1970s. Apartment buildings fan out from the pristine, white shells of the church, which commemorates Christianity’s 2,000th anniversary. The project’s sponsor, the Italcementi Group, the world’s fifth-largest cement producer, enhanced Meier’s trademark white exterior with a titanium-dioxide (TiO2) coating that essentially cleans itself.
Tests also show that construction products, in this case, cement, that contain TiO2 help destroy pollutants. Companies are now developing photocatalyzing, TiO2 products that can also be used in paint, plaster and paving materials. Two highly reactive oxidizers form when TiO2 — the same stuff that makes toothpaste white and paint opaque — is exposed to UV light, in a wavelight below 385 nanometers, and water vapor.
These aggressive radicals and ions attack and kill bacteria, and the contaminants more readily wash away from the water-loving surface than from hydrophobic tiles. Because organic materials are broken down into carbon dioxide and water, and then easily flushed out, a building’s appearance remains pristine. Meier required that the building’s “sails” must maintain their whiteness.
The patented pollution-reduction technology, which in Italy is known as cemento mangiasmog, or “smog-eating cement,” was discovered in the late 1970s, but only recently was it widely implemented. Streets in Segrate, near Milan, have been repaved with Italcementi’s compound, TX Active. The same system has been applied to the new Air France headquarters at the Charles deGaulle airport. Long Beach, CA-based Toto Frontier applies a 1-micron layer of TiO2 to ceramic blanks for use in hospitals, public restrooms and hard-to-reach rooftops.
Whether TiO2 is the Green Knight remains to be seen — it may produce reactions more toxic than the pollutants it attacks.