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Friday, May 8, 2009

Bendable Concrete Heals Itself after a few days of light rain

A slab of self-healing concrete bends under 5 percent tensile strain, the force needed to stretch a material by 5 percent of its initial size. While ordinary concrete would crumble under such pressure, the new material forms micro-cracks that can then auto-seal after being exposed to water and carbon dioxide, researchers said in March 2009.

The new concrete composite can bend into a U-shape without breaking. When strained, the material forms hairline cracks, which auto-seal after a few days of light rain. Study co-author Victor Li of the University of Michigan in Ann Arbor said dry material exposed by the cracks reacts with rainwater and carbon dioxide in the air to form "scars" of calcium carbonate, a strong compound found naturally in seashells which flexible material is just as strong after it heals.

Similar self-healing concrete has already been used inside the core of Osaka, Japan's tallest residential building, a 60-story structure. The material was also used in a bridge built in 2006 over Interstate 94 in Michigan, where it eliminated the need for traditional expansion joints.

Victor Li commented the new concrete apart from reducing maintenance requirements, is very quiet. Self-healing concrete is now being considered for use in irrigation channels in Montana which a cost-saver in the long run, due to its reduced maintenance needs and energy demands. Also eliminates the need to buy and install devices that counter seismic activity.


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