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More adventures of bacillus pasteurii - mending concrete

The efficiency with which bacillus pasteuriimanufactures calcium
carbonate and glues things together makes for ways in which our microbial friend
can assist us beyond just preventing earthquake damage and sculpting deserts
(see the previous post) and here’s, literally, a concrete example. But I should point out here that the image above is quite unrealistic, simply a Sandglass photoshop special.

The recipe for basic concrete is simple and has been around for a long time.
The ancient Egyptians knew how to make it (there is a lively debate as to
whether the pyramids, at least in part, are made of concrete), and the Romans
perfected the formula. The fundamental ingredients are around 75 percent sand
and gravel, 15 percent water, and 10 percent cement. The cement, cooked from
materials such as limestone and clay, is the chemical glue; the hardening of
concrete is not simply due to drying, but involves complex chemical reactions.
The physical characteristics of the sand, its size and shape, influence the
properties of the concrete, but because of the importance of chemistry, the
composition of the sand and the other ingredients is critical. The wrong
impurities will ruin the quality of the concrete.

The global demand for concrete is massive: after water, concrete is the most
consumed material on Earth. Every year, the equivalent of more than 400 million
dump trucks of concrete is transported to construction sites. Every man, woman,
and child on the planet “consumes” around forty times their own weight in
concrete per year. Which is, of course, an average—for residents of the Western
world, it’s much more, despite the fact that around half the world’s concrete
production and consumption today is accounted for by China.

But concrete is vulnerable to deterioration, corrosion, and cracks, and the
consequent damage and loss of strength requires immensely expensive remediation
and repair. So, is there a way in which incipient microscopic fractures in
concrete can self-heal? The answer, thanks to our microbial friend, would seem
to be yes, through the process referred to as biomineralisation,
microbiologically induced calcite precipitation (MICP). Around the world,
research groups are working and collaborating on different approaches to turning
this into reality, but the principle is quite simple. The chemistry of concrete
is alkaline, but fortunately, bacillus pasteurii tolerates this - it
simply needs nutrition, space to work, and a little encouragement. A team led by
Henk Jonkers at the Delft University of Technology in the Netherlands are well
on the way to accomplishing this, through actually mixing living bacteria, along
with calcium lactate, an organic compound that such bacteria convert to calcium
carbonate, into the concrete to begin with. They found that, as the concrete
cured, incipient cracks were effectively sealed with calcium carbonate. There
remain problems of keeping the microbes alive for a long period of time, and
retaining sufficient microscopic space in the concrete for them to have room to
maneuver, but progress is being made (the addition of clay to the mix provides a
safe haven). And, importantly, the more effective this process proves, the less
concrete we will have to manufacture and the lower the associated carbon dioxide
emissions from making cement.

As a recent article in The Economist concluded, “If the process can
be scaled up, it may be prove that the best way to preserve concrete is to
infect it.”

[for details on the work of Henk Jonkers, see http://www.tudelft.nl/live/pagina.jsp?id=8691221d-ebab-4841-97cb-1cfacad3a4bc&lang=nl,
a recent conference presentation,
a link to the abstract of the group’s most recent paper here,
and The Economistat http://www.economist.com/science/displaystory.cfm?story_id=13570058.
For work at the South Dakota School of Mines and Technology, see http://adsabs.harvard.edu/abs/2001SPIE.4234…168R,
at the S. V. National Institute of Technology in India, http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1285418,
and for non-bacterial approaches, http://www.eurekalert.org/pub_releases/2009-04/uom-scf042209.php.] SIGNATURE

Comments

Concrete In Michigan (2009-12-30):

The technology of self healing concrete is simply amazing. Thanks for the informative post!

Jegan.R (2012-01-13):

where is it manufacture?

Sandglass (2012-01-13):

To the best of my knowledge, it’s still in the research laboratories.

Liang (2012-02-10):

This technique seems to be a hot topic at the moment. Instead of concrete self-healing, soil strength enhancement is more attractive.

ken scarborough (2017-07-05):

Check out this video…I think yo will be amazed. We are experimenting with bacillus pasteurii to use with this product as well.
https://www.indiegogo.com/projects/brockrete-building-better-environment-green#/

Sandglass (2017-07-06):

fascinating - and impressive. Good luck!