Thursday, January 06, 2005

Clean Air Concrete

Concrete is becoming more and more versatile as scientists and engineers develop new ways to improve an old substance. The Church above is made with a type of concrete which is self cleaning so that it never darkens from pollutants and may in fact improve air quality. Other types include a concrete which is semi transluscent and lets light pass through and types which are stronger and longer lasting. Click on the title above to read the whole article.

There are many simple ways to modify the properties of concrete. Tweaking the ratio of the ingredients can change the material's strength or roughness, for instance. Modern concrete also contains chemical additives that affect the material's physical properties, such as the fluidity or the time it takes to harden.

Eliminating the need for steel bars has other advantages, including lengthening the lifetime of structures. Consider the deck of a bridge. In the winter, when ice-clearing salt dissolves and seeps into the concrete, it corrodes the steel. The corrosion causes the concrete to detach itself from the reinforcing metal and to crack. A conventional concrete deck needs major repairs or reconstruction after about 25 years, says Perry. "A Ductal deck should last at least twice as long," he adds.

The material has already found its way into several pedestrian bridges around the world, as well as a light rail transit station in Calgary, Alberta. The canopies that form the roof over the station's platform and the roof's support columns are made entirely of Ductal. The canopies provide protection from the elements, can withstand high winds, and support heavy snow loads.

A translucent concrete material contains glass optical fibers that transmit light through the entire length of the block. It can bring sunlight through a wall.

With these blocks, architects can design and build a large variety of structures, ranging from translucent concrete walls to floors lit from below. LiTraCon has already received a number of requests from architects interested in the material, says Bittis. One firm in New York has proposed using the new concrete in its design of a police college in Kuwait City. Because concrete is an excellent insulating material, the building would protect against the desert heat while letting through some sunshine.

New forms of concrete might also abate environmental pollution. Scientists at the Italcementi Group in Bergamo, Italy, have developed a self-cleaning concrete that keeps buildings from turning black from pollutants in the atmosphere. Luigi Cassar and his colleagues at the research branch of Italcementi made the concrete by adding particles of the white pigment titanium dioxide to the cement component.

The material has applications beyond keeping concrete surfaces bright. Cassar's group has found that the concrete can actually clean the air. The company is investigating coating buildings and roads with the photocatalytic material. Computer models of the material and urban pollution predict that covering 10 to 15 percent of the roads and building surfaces in a city such as Milan, Italy could reduce air pollution by 40 to 50 percent, Cassar's group calculates.

The efforts to bring concrete to new heights of function and form, however, is almost certain to transform the traditional perception of concrete as a cold, drab, low-tech material. Its use is likely to extend as far into the future as it reaches into the past.


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