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Grad student may have discovered economically feasable smart concrete

Most people think of driveways and sidewalks when concrete is mentioned. Concrete is also used as a structural building material in many large buildings around the country. The problem with concrete as a building material is that as it develops cracks, the material becomes weaker.

Researchers are currently investigating ways to make smart materials that can heal themselves from cracks and other minor imperfections as a way to prolong the life of the material and increase its strength. A grad student named Michelle Pelletier from the University of Rhode island has made a discovery that may one day lead to smart materials that are cost effective to produce and easy to use.

Pelletier is a master's degree candidate and has developed a method of embedding microencapsulated sodium silicate healing agents directly into concrete. The idea is that the tiny microcapsules, which hold the sodium silicate agent that reacts with calcium hydroxide naturally in concrete, will rupture when cracks form and release the repairing agent.

When the sodium silicate inside the microcapsules reacts with the calcium hydroxide in the concrete a chemical reaction causes a gel-like material to form that can fill cracks and pores in the area of the crack and hardens in about a week.

"Smart materials usually have an environmental trigger that causes the healing to occur," explained Pelletier, who is collaborating on the project with URI Chemical Engineering Professor Arijit Bose. "What's special about our material is that it can have a localized and targeted release of the healing agent only in the areas that really need it."

Tests of the self-healing concrete have shown that when stressed to near breaking the concrete with the microencapsulated sodium silicate is able to regain up to 26% of its original strength. Standard concrete when stressed to similar levels only regains 10% of its strength. Improvements in the

Another potential benefit of the new self-healing concrete being studied is if by immediately filling cracks in the concrete, water can be prevented from reaching the steel reinforcement bars that are used to add strength to concrete. Water getting to the steel reinforcement bars causes the bars to rust leading to reduced strength.



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RE: thoughts...
By Smartless on 5/25/2010 2:14:51 PM , Rating: 2
Now now, let's not be too hasty. There have been many other inventions in the "new discovery" category that are far less likely to see application.

1. True that a week is a long time, but this may be great for say something like a storm with a relatively short time-frame of high stress. During that time, concrete depends on its steel to resist the tensile stress which can crack the concrete covering it. If this stuff fills the gap, that's a world of difference.
2. You are correct. High-test or ballistic concrete may not see this, but hey this is the design stage. When admixtures came out, people thought 10,000psi concrete was pretty good. Parking aprons maybe not, but bridges, buildings, sea walls... possible.
3. It doesn't necessarily have to be mainstream. Ballistic concrete and high strength concrete used in some bridges can have pieces of kevlar in it for added tensile strength.

I think usage of this would probably see light of day faster than fuel cell for everyday cars.


"There is a single light of science, and to brighten it anywhere is to brighten it everywhere." -- Isaac Asimov











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