Mar
31
2009

Building Better Bridges, and Other Concrete Details

The new I-35W bridge: now bigger, stronger, and greener.
The new I-35W bridge: now bigger, stronger, and greener.Courtesy anjouwu
Ever stand on a sidewalk and wonder about the concrete beneath your feet? Where did it come from, and how did this hard grey material get to be pretty much everywhere? Though you may not think about it at all, concrete is used more than any other building material in the world. In fact, concrete is so ubiquitous that the production of concrete contributes 5% of the world's human-caused carbon dioxide emissions to the atmosphere.

Add it all up and it starts to look like concrete is more than just the stuff of sidewalks and building blocks. Concrete is a V.I.P. (which is how I like to refer to Very Important Polluters).

While concrete is a huge contributor of CO2, it also has loads of potential to be an innovative and important "green" material that helps us to build stronger and more environmentally friendly roads, bridges and buildings. This really great article from the New York Times science section explains the basics of concrete chemistry, and how new concrete mixes are being developed that are not just stronger and better for buildings, but that also can scrub carbon from the air.

Here in the Twin Cities we have our own example of cutting-edge concrete in the I-35W bridge, which was built to replace the bridge that collapsed in 2007, killing 13 people. You might not realize it as you pass over this bridge, but it's made of many different mixes of concrete, each developed to do a particular job.

Some of the concrete in the I-35W bridge was mixed and cured (that's what they call the hardening process) to be strong and stable, others to resist the road salts and other effects of weather and climate in Minnesota. The wavy concrete sculptures on the bridge even scrub pollutants from the air, In fact, they stay white because of a chemical process that uses the sun to help break down staining pollutants. Who knew concrete could be so fascinating?!

More Than You Ever Wanted to Know About Concrete

Science Buzz Posts on the I-35W Bridge Collapse

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