Saturday, November 20, 2010

Concrete Glue

One has to love this story.  One can not imagine a problem less likely to get truly solved, and of course it remains to be seen if this glue manufacturing protocol actually is practical at all.

Besides, simply replacing most static concrete is cheap and easy as in sidewalks and the like.  And repairing concrete structure reinforced by rebar may unwisely extend the life of failing rebar that has rusted in place and generated much deterioration of the concrete.

We have engineered failure modes into our designs that accommodate concrete cracking behavior.  Thus localized patching may be successful in transmitting failure modes elsewhere.

It will certainly have a clear cosmetic application as aging cement does chip and spall.  Of course all new cement sports curing fractures that are now self healing.  It should be possible to refinish old cement using this method.

'Glue' producing bacteria used to fill gaps in cracking concrete
23:04 November 16, 2010

Earlier this year we took a look at the development of self-healing concrete that repairs its own cracks using a built-in healing agent. While this kind of technology holds promise for construction in the future, it’s not so useful for the vast amounts of existing concrete in need of replacement or repair. UK researchers have come up with a solution to this problem that uses bacteria to produce a special "glue" to knit together cracks in existing concrete structures.


A team of students from Newcastle University created bacteria and programmed the genetically modified microbe to only start germinating when triggered by the specific pH of concrete. The researchers have also built in a self-destruct gene to ensure bacteria are unable to survive in the environment if they fail to germinate. Once the cells have germinated, they swarm down the fine cracks in the concrete and know they have reached the bottom when they start clumping.

This clumping activates the cells to differentiate into three types: cells which produce calcium carbonate, cells which become filamentous to act as reinforcing fibers, and cells which produce a Levans glue which acts as a binding agent. The calcium carbonate and bacterial glue combine with the filamentous cells, ultimately hardening to the same strength of the surrounding concrete to form what the researchers have dubbed "BacillaFilla" which knits the concrete structure together again.

Helping cut CO2 emissions

With concrete production a major contributor of global carbon dioxide emissions, the BacillaFilla could provide a way to repair instead of replace existing concrete structures.

Joint project instructor Dr Jennifer Hallinan explains: “Around five per cent of all man-made carbon dioxide emissions are from the production of concrete, making it a significant contributor to global warming. Finding a way of prolonging the lifespan of existing structures means we could reduce this environmental impact and work towards a more sustainable solution.”

“This could be particularly useful in earthquake zones where hundreds of buildings have to be flattened because there is currently no easy way of repairing the cracks and making them structurally sound,” she added.

The Newcastle University students designed the BacillaFilla as their entry for this year's International Genetically Engineered Machines contest (iGEN) that is run out of MIT. The team took out Gold for their research, which was up against over 130 entries.

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