Cement cleans itself—and the environment, too
More than two years after the grand opening of the Richard Meier-designed Jubilee Church in Rome, the structure’s triple-shell concrete façade appears as gleamingly white as the day the church opened its doors.
How does the Jubilee maintain its pearly white sheen? The secret is in the cement.
The New York-based architect specified an experimental white-cement mix from Italian cement supplier Italcementi that is self-cleaning. Italcementi is among several cement companies marketing so-called “photo-active” cement, which uses daylight to breakdown harmful pollutants, such as nitrogen dioxide, carbon monoxide, VOCs, and formaldehyde, that stem from vehicle exhaust, industrial emissions, and other sources.
The special cement is formulated with selective amounts of titanium dioxide that, when exposed to ultraviolet rays, triggers a catalytic reaction that oxidizes organic and inorganic substances deposited on the surface. The by-products of this photocatalytic reaction—carbon dioxide and harmless inorganic salts, such as calcium nitrate, sulfate, and carbonate—are then washed away by rainwater, thereby cleaning the concrete surface. By eliminating the organic molecules, the reaction also indirectly prevents bacteria, dust, and dirt from sticking to the surface. The technology has been applied to other building materials, including glass, but cement has significant promise from an environmental standpoint because of the vast amount of concrete structures and surfaces that cover the planet. An added benefit to self-cleaning cement is its potential to help clean the surrounding air. A test in Milan in 2003 by Italcementi, for example, showed that nitrogen oxide levels were reduced by up to 60% on and around 75,000 sf of road surface that was paved with photocatalytic cement. But other than a few isolated experiments, very little data exists on the “depollutioning” performance of self-cleaning cement. Also, Building Teams can expect to pay a premium for self-cleaning cement, according to Italcementi. The company suggests, however, that owners will make up the up-front expenditures with reduced maintenance costs.