Minneapolis Bridge Sculptures Eat Air Pollution

On the I-35W St. Anthony Falls Bridge in Minneapolis, a pair of 30-foot tall cement statues stands guard over the freeway. Designed as three wavy lines reaching toward the sky, the sculptures are a visual representation of the symbol for water used on maps around the world. They each mark the points on the bridge where the Mississippi River is crossed.

Besides being beautiful, the Minneapolis bridge sculptures eat air pollution. That's right. The concrete that the sculptures are made from literally sucks the pollution from the air.

How do the Minneapolis St. Anthony Falls Bridge sculptures work?

The concrete used to build the sculptures is special photocatalytic concrete called TX Active. What this means is that the concrete reacts with ultraviolet light. The bridge sculptures contain a compound that makes them self-cleaning, so they should stay white for as long they stand. The sculptures also pull pollutant particles like carbon monoxide, sulfur dioxide, and nitrous oxide out of the air and convert them to less harmful substances.

Photocatalytic concrete works because of nanotechnology. On a molecular level, the nanotechnology speeds up the oxidation process on the surface of the sculptures, which is what leads to the self-cleaning and smog-reduction that we can see.

What are the benefits?

The I-35W Minneapolis St. Anthony Bridge sculptures were completed in September 2008. Since then, AAA and the U.S. Chamber of Commerce have chosen it as one of America's top ten best transportation projects.

Though it's hard to say exactly how much smog has been eliminated due to the photocatalytic concrete used in the sculptures, the bridge has several other environmental merits. It's built to last at least a hundred years (which should be a relief to anyone affected by the previous bridge's collapse), and it can easily incorporate light rail transit into its existing design if public transportation expands in Minneapolis.

Another future environmental benefit to using photocatalytic concrete in the Minneapolis St. Anthony Falls Bridge sculptures is that no harsh cleaners will ever need to be used to preserve their beauty. That saves a lot of chemicals from being washed into the Mississippi River.

Is anything else being made from the same material?

Photocatalytic concrete has been used in Europe for the last ten years, though it's just beginning to get noticed in the United States. Jubilee Church (also known as the Dives in Misericordia) in Rome has giant, 80-foot photocatalytic concrete sails. Photocatalysts are also used in paving sidewalks in Tokyo to help cut down on air pollution there.

Resources:

Concrete Network: http://www.concretenetwork.com/concrete/concrete-statuary/design-ideas/bridge-sculpture.html

Cement Americas: http://cementamericas.com/mag/minneapolis_bridge_photocatalytic_concrete_1108/

New York Times: http://www.nytimes.com/2009/03/31/science/earth/31conc.html

Minnesota Department of Transportation: http://projects.dot.state.mn.us/35wbridge/