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April 30th, 2009

Video of the week II – Self-healing concrete

Published on April 30th, 2009 | By: pwray@ceramics.org

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Following on the heels of our first  Video of the week, this is look at Victor Li’s latest innovation: self-healing concrete.

Cement and Concrete Research is soon to publish a paper by Li, who is a professor in material science and engineering at the University of Michigan, that describes a type of concrete that forms many tiny cracks when overloaded instead of a few large ones, leading to a process in which the concrete effectively “heals” itself.

Even after a 3 percent tensile strain, Li’s samples recovered nearly all of its original strength. “We found, to our happy surprise, that when we load it again after it heals, it behaves just like new, with practically the same stiffness and strength,” Li said. “Self-healing of crack damage recovers any stiffness lost when the material was damaged and returns it to its pristine state. The material can be damaged and still remain safe to load.”

Li and his research group have spent more than a decade developing what he calls engineered cement composites. An early version of this ECC is what made the bendable concrete possible. The current version of ECC keeps cracks under 60 micrometers. The cracks, though small, expose small amounts of unhydrated cement in the concrete. When the concrete is subjected to water and carbon dioxide, it forms a tiny calcium carbonate “scar.” Li found in his lab that between one and five wet-dry cycles are needed to reach final level of healing.

This kind of thing is always great stuff, but cost-benefit analyses often deflate some great innovation. Here, the question is whether a signficant extension in the lifespan of something like a concrete highway can offset the premium paid for ECC-enhanced materials that at one point were looking like they would cost three-times as much as traditional concrete. Nevertheless, U-M says it is is pursuing patent protection for the intellectual property, and is seeking commercialization partners to help bring the technology to market.

Li is supposed to be delivering a keynote address on self-healing concrete at the International Conference on Self-Healing Materials in Chicago in June 2009.

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2 Responses to Video of the week II – Self-healing concrete

  1. Ray Dunaway says:

    I am interested in protecting reinforced concrete submersed in salt water. I live in a community of floating homes built on concrete barges. When the sea water penetrates the concrete and contacts the rebar the rebar oxidizes and swells, causing the concrete to spall. We need a fast setting coating or one that may be applied underwater. We have about 6 hours a day when the hulls are out of the water due to tide action so we need something that may be applied and cured sufficiently to be immersed in seawater within that time frame. Since these houses displace upward of 100 tons and are difficult to move we prefer to get something than may be applied in place.

  2. josé sancho says:

    I find your development very interesting, in particular if your polished concrete could be used for movable structures, very much used now in city pavements over metallic (steel) supports where I can see a lot of cracks in the stone material used for covering it (like marble). City pavements can be payed at higher prices than material used for motorway. In fact is a maisy to see the very bad aspect of marble used on a railway station covering of my town in Oviedo (Spain), than with your development if can be coloured could be everlasting and beautiful . Good luck.

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