Seashell-Like Concrete Fills In Its Own Cracks

Forget politics for a minute. America's infrastructure--our roads, sidewalks, and bridges--is in bad shape. Recent assessments show that one in four U.S. bridges supports more traffic than was originally intended, or is in need of significant repair. A full third of all U.S. roadways are in sub-standard condition. There are lots of reasons why infrastructure has been allowed to decay, but most revolve around money.

In most cases, repairing a road or bridge just delays the inevitable. Truth is, after about 25 years, concrete that's exposed to the elements 365 days a year is going to break down. But what if the next generation of roads and bridges weren't built with the same old concrete? The Advanced Civil Engineering – Materials Research Lab at the University of Michigan recently unveiled a new type of flexible, self-repairing concrete that could revolutionize our infrastructure and save local governments millions.

Inspired by examples of self-healing in nature, like skin and bones that heal their own damage and vines that repair themselves when broken or torn, the scientists at the University of Michigan were determined to create a smarter building material. What they came up with is new a form of concrete that uses microfibers in the place of coarser bits of sand and gravel that traditional cement mix uses. The fibers allow the final composite to bend with minimal fracturing and if fracturing does occur, the cracks tend to be less than 50 microns wide.

"When these tiny cracks form, the dried concrete absorbs moisture from the air," write the researchers. "When it does this, the concrete in the crack becomes softer and eventually "grows" until the crack is filled in. At the same time, calcium ions within the crack absorb the moisture along with carbon dioxide from the air. This reaction forms a calcium carbonate material that is similar to the material found in seashells. This regrowth and solidifying of calcium carbonate renews the strength of the cracked concrete."

As points out, this revolutionary material could save municipal governments millions of dollars normally spent on skilled labor to remove and replace sections of road that have formed cracks and potholes. If commercially successful, maybe they can use the savings to fix those rickety bridges we drive over every day...

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