March 24, 2010

DAVIDE LUSSETTI

Rome’s Dives in Misericordia Church was one of the first buildings to use a special form of self-cleaning photocatalytic concrete.

Innovation

New technology allows concrete to come clean

DAN O’REILLY

correspondent

A recently completed major renovation of the Sun Life Financial Centre in Waterloo is one of a small, but growing number of projects where special cement has been incorporated so that buildings can harness the sun to self clean and de-pollute themselves.

The financial centre’s concrete “smartcast” roof top pavers were manufactured by Hanson Hardscapes using a unique formula, which includes special aggregates and admixtures with TX Active photocatalytic white cement.

First used in 2001 in the construction of a landmark church in Rome, the cement has been used in the construction of several prestigious architectural-style buildings in Europe and has now established a foothold in the North American construction market.

The cement, which contains titanium dioxide, speeds up the natural oxidation process in the concrete, said Dan Schaffer, product manager for Essroc, the North American subsidiary of the Italcementi Group, the developer.

It’s a process known as photocatalysis, in which a substance known as a photocatalyst uses light to expedite the rate of a natural oxidation process, he explained.

“There’s nothing magical about it. Essentially sunlight is being used as a strong agent to oxidate primary pollutants such as sulphur dioxide, VOCs (volatile organic compounds) and carbon monoxide,” he said.

The photocatalytic action destroys the various organic air pollutants, such as car exhaust fumes, industrial and residential emissions that come in contact with the concrete surface.

As a result, buildings can maintain original appearances.

The cement was used for the first time in the production of the precast panels that form the three distinctive “sails” of Rome’s Dives in Misericordia Church, designed by American architect Richard Meier.

It was created by the Italcementi Group to meet the rigid specifications of the architect and Vatican officials, who wanted a church that would maintain its appearance in Rome’s smoggy environment, said Schaffer.

The successful application subsequently led to its use in the building of a police headquarters in Bordeaux France and sparked a major independent technical study on its uses by members of the PICADA PROJECT, a non-profit organization comprised of manufacturers and research testing laboratories.

It was introduced in North America in 2007 and has been used in the construction of about 20 buildings such as a 75-foot high Bell Tower at a college in Georgia.

“At that height, keeping the precast panels clean through conventional methods would be difficult and costly,” he said.

All of the buildings are in the United States, with the exception of the Sun Life Centre.

For now the cement is only manufactured at Essroc’s Virginia plant. But Schaffer is confident more plants will be opened in other parts of North America once the product becomes better known and used.

“It is becoming more and more accepted by architects and engineers. The feedback has been very positive.”

The one big drawback is the price, which averages out to be an additional $1 per square for every square inch of thickness.

However, it’s only used in the face mix and certainly wouldn’t be used for hidden concrete structures. Some of its applications would include concrete sidewalks, architectural precast panels and concrete roof tiles, said Schaffer.

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