
Using bacteria to make self-healing cement - vinnyglennon
https://www.thestructuralengineer.info/news-center/news/item/589-using-bacteria-to-make-self-healing-cement
======
samgtx
>Being mixed with concrete and distributed evenly throughout it, they can lay
there in a dormant state for up to 200 years; only when the concrete cracks,
air and moisture awaken the bacteria which use the calcium lactate as a food
source and start to produce limestone, sealing off the cracks in 3 weeks’
time. The technology, currently able to seal cracks of any length but only up
to 0.8 mm wide, was a finalist for the European Inventor Award 2015, an
initiative of the European Patent Office (EPO).

That's brilliant. I wonder what the cost increase would be for including this
solution v. the cost of traditional repairs.

~~~
justinmchase
The article says it costs about twice as much.

> Currently the cost of this new technology is still considered prohibitive,
> as it is twice the cost of regular concrete manufacture (70-80 € / m3),
> making it only viable for projects where leakage and corrosion are
> particularly problematic, such as underground and underwater structures.

What's funny to me though is that they consider this cost prohibitive despite
the expected theoretically longer life without replacement or maintenance.

~~~
LegitShady
How often do you think most concrete structures (with only minor cracking like
in the article) undergo serious rehab? Maybe once in their service life.

Also, when planners are choosing between alternatives, net present value (NPV)
is calculated which takes into account predictable maintenance, so the cost of
future repairs is already considered in these decisions.

Civil engineering is also not computer engineering. There is no agile
development and you have to get it right the first time. The industry as a
whole is not quick to adopt new technologies without seeing them proven in the
field relatively thoroughly.

~~~
monocasa
> Civil engineering is also not computer engineering. There is no agile
> development and you have to get it right the first time.

Eh, that's a little overstated. You'd be surprised how many buildings and
bridges have major refits when it becomes obvious that their design didn't
live up to expectations.

~~~
agumonkey
There's a youtube video about a hybrid version of that, some famous civil
engineer forgot a tiny detail in a massive project. Student of his raised the
issue, he actually listened, and managed to plan a last minute
redesign/overhaul without anybody knowing (at first).

~~~
LegitShady
It's the Citicorp tower you're talking about.

~~~
agumonkey
most probably, and thanks to you, I found the video again

[https://www.youtube.com/watch?v=Bv2YQnT6pSo](https://www.youtube.com/watch?v=Bv2YQnT6pSo)

------
epiphanitus
Fun Fact: Much of the Great Wall is still in very good condition thanks to its
amazingly resilient mortar. The secret ingredient: sticky rice.

[https://www.telegraph.co.uk/news/worldnews/asia/china/778584...](https://www.telegraph.co.uk/news/worldnews/asia/china/7785842/Great-
Wall-of-Chinas-strength-comes-from-sticky-rice.html)

~~~
dmos62
I love hearing about possibly competitive low-tech solutions.

------
nsb1
<puts down Cat's Cradle>

"Are you double-dog sure this stuff can never get out in the wild?"

~~~
glloydell
There is absolutely no way this could possibly go wrong.

~~~
smrq
While I'm sure I agree with you, this comment reads like some famous last
words!

------
JadeNB
The materials scientist Mark Miodownik discusses this and other miracles of
modern, well, materials science in his marvellous book "Stuff matters"
([https://books.google.com/books/about/Stuff_Matters.html?id=_...](https://books.google.com/books/about/Stuff_Matters.html?id=_5yUAwAAQBAJ)).
I found it fascinating—though, fair warning, the material on cement was by far
the most fascinating to me.

~~~
JadeNB
By the way, I just discovered he's got a new (to me) book, my copy of which is
titled "Liquid rules" (apparently a later printing of a book originally just
called "Liquid")
([https://books.google.com/books?id=7p_FwQEACAAJ](https://books.google.com/books?id=7p_FwQEACAAJ)
).

------
mrfusion
What’s cool about this is could it save the cost of making expansion joints?

Edit. What I mean is you could do really big pours instead of sections. Think
a mile long sidewalk with no sections.

~~~
munk-a
I don't believe so - those expansion joints exist IIRC to account for the fact
that cement is quite temperature volume stable... but it isn't temperature
inert. The seasonal temperature swings cause expansion and shrinking of cement
and, especially on the scale of a bridge, those slight volume changes add up.

I imagine this tech would allow shrinkage during the winter to be
automatically repaired if it manifested as hairline gaps - but when summer
rolled around you'd get a severe amount of buckling the cement expanded...
then those buckles might partially repair - be reinforced when gaping occurred
in winter - then buckle even more come next summer.

------
ddxxdd
I would like to understand the science behind how bacteria can live under the
50 gigapascals of pressure that one would find in the base of a skyscraper.

My intuitions currently tell me that finding life underneath such mechanical
stress is comparable to finding life inside the lava of a volcano or on the
surface of the sun.

~~~
YayamiOmate
Well, there are bateria living on chemical energy deep down in the oceans near
volcanoes, that's not far from your example.

~~~
Gibbon1
There are actually bacteria living in rocks thousands of feet below the
surface.

------
Hitton
Ancient Romans had kinda similar technology, although chemically not bacteria
based.

[https://www.nature.com/news/seawater-is-the-secret-to-
long-l...](https://www.nature.com/news/seawater-is-the-secret-to-long-lasting-
roman-concrete-1.22231)

------
UI_at_80x24
Wasn't it discovered that these bacteria are what make "Roman Cement" so much
better then modern 'Portland Cement'? (or was I supposed the RTFA?)

~~~
ThrustVectoring
The primary difference between Roman and modern cement is that Roman cement
does not have reinforcing steel in it and cannot support loads that put it
under tension stress. This reinforcing steel is what fails with age - cracks
develop, let in air, and corrode the steel. No steel, and what you have is
basically a shaped rock, and that can last a really long time.

The downside, of course, is that not being able to resist tensile loads
severely limits the designs you can make with concrete. Reinforced concrete is
_significantly_ more useful than unreinforced concrete.

~~~
dustfinger
I wonder if it would be feasible to replace the steel reinforcement rods with
ceramic? No iron no rust.

I also wonder if concrete might bond better with ceramic. My understanding is
that concrete does not bond well with steel.

~~~
ThrustVectoring
It'd be a material engineering feat to get the required plasticity and tensile
strength out of ceramics. The plasticity is probably more worrying in practice
- the failure mode of rebar rusting is usually visible to inspection and slow
enough that action can be taken to ensure that the structure remains safe. The
failure mode of a brittle reinforcing member suddenly failing is much more
worrying from a safety perspective.

~~~
ggcdn
In structural engineering we call this plasticity "ductility", but you're
exactly right. We want ductile failures not sudden brittle ones, and that can
only be achieved with yielding reinforcing. Ceramics generally will fail
brittly, or cause the concrete to crush if the member is over-reinforced.

------
inflatableDodo
Sounds like a great material for floating arcologies.

------
blacksqr
"I'm beginning to think I can cure a rainy day!"

------
ninju
please apply date [2017] to title as the article is old

>Friday, 12 May 2017 01:00cat

