Self-healing and self-repair is a common theme in biological systems from trees to human skin. The less severe the damage is to an organism, the easier it is for the organism to repair itself and for the repair to be strong and long-lasting.
Concrete cracks for many reasons: just for starters, the heating and cooling of changing seasons make it expand and contract, and the stress produced as the freshly poured goo dries and shrinks in volume, pulling against its underlying metal supports, can also cause cracks.Several researchers suggests this new form of concrete which 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. 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.
Apparently, Dutch researchers are also testing a new way to deal with the problem of cracking concrete: bacteria that, when exposed to water, form limestone.The concrete mix they've developed contains small ceramic pods filled with dormant spores of the bacteria and nutrients (calcium lactate) to feed them. In solid concrete slabs, these spores remain dormant, but when the concrete cracks and water seeps into the ceramic pods, the bacteria spring into action, using the calcium lactate to form calcite, one of the two primary components of limestone, which fills the crack. In the lab, the bacteria can fill cracks up to 0.5 millimeters wide.Not only do the bacteria work to plug cracks in the concrete, the process of doing so uses oxygen present which would otherwise be involved in the corrosion process of the steel bars.
The rigidity of traditional concrete leads to the formation of large cracks that can seriously degrade the integrity of important structures. Furthermore, when damage does occur to concrete, expensive and resource-consuming measures must be taken to repair the concrete, usually from the outside. Or, if repair measures are insufficient, the structure must be demolished and rebuilt which further expands the need for resources. Self-healing concrete could vastly increase the life of concrete structures, and would remove the need for repairs, reducing the lifetime cost of a structure by up to 50 per cent.Over seven per cent of the world's CO2 emissions are caused by cement production, so reducing the amount required by extending the lifetime of structures and removing the need for repairs will have a significant environmental impact.
This Self-healing Concrete Repairs Itself with Bacteria - 80beats | DiscoverMagazine.com. (n.d.). 80beats. Retrieved May 15, 2014, from http://blogs.discovermagazine.com/80beats/2012/11/02/this-self-healing-concrete-repairs-itself-with-bacteria/#.U3QbpfldVqw
This is a great idea. I wonder if there is a way to create solmething that is as sturdy and solid as concrete but with an adaptive elastic element to it. That way, buildings could shift and move over time due to weather and vibrations but retain its strength without cracking.
ReplyDeleteThis seems very exciting but somehow the idea of bacteria in walls of buildings is a little uncomfortable. Maybe in tar for roads but say for instance this self healing concrete is used in a building, in time the bacteria colony would grow, and they'll keep growing all the while trying to broaden their niches. Majority of bacteria are not harmful but extensive research to study the long term effects of introducing microbes into physical infrastructure has to be done.
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