
Bacteria and sand engineered into living concrete - hhs
https://www.eurekalert.org/pub_releases/2020-01/cp-bas010920.php
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frandroid
We already have slow-curing low-emissions concrete, which has existed for
centuries. Fast setting is a core feature of modern (Portland) concrete, and
any "replacement" which doesn't do that is not a replacement at all. Companies
want to build their 40-story towers in 6 months, not 6 years.

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jbotz
Our modern concrete has not existed for "centuries"... Portland cement was
invented about 150 years ago, and steel-reinforced concrete started being used
just over 100 years ago.

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frandroid
I'm talking about lime-based cement, which predates Portland cement and steel-
reinforced concrete. Portland cement is a huge source of CO2 emissions.

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feintruled
This reminds me of the JG Ballard story Venus Smiles, which I found whimsical
and scientifically ridiculous at the time of reading, where an artist creates
a living sculpture which basically makes a hell of a racket and grows itself
out of control. Panicking, the owner has it cut up and sold for scrap, only to
start hearing the same noises start when he is in new buildings - the tainted
metal has been used in construction projects from the melted down scrap and is
proliferating - "The whole world will be singing."!

Reading this news story it seems that one could retrofit a bacteria based
scientific explanation - perhaps not so outlandish after all. What an amazing
futurist he was!

[https://en.wikipedia.org/wiki/Venus_Smiles](https://en.wikipedia.org/wiki/Venus_Smiles)

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Ericson2314
Can it use desert sand rather than riverbed sand?

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g82918
Not really, desert sand and riverbed sand have different characteristics with
regards to smoothness and grain size, etc.. You really can just use desert
sand.

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Ericson2314
I elsewhere read much concrete is made with rare, far away, environmentally
damaging illegally dredged riverbed sand, because desert sand (or other more
available less environmentally precious substitutes) were unsuitable.

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hijinks
that's great and all but it's the sand part that's making concrete expensive.
The type of sand to use is becoming harder and harder to source

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knolax
> The brick needs to be completely dried out to attain the maximum structural
> capacity (i.e., strength), but at the same time, drying stresses the
> bacteria and compromises its viability. To maintain structural function and
> ensure microbial survivability, the concept of optimum relative humidity and
> storage conditions is critical. Utilizing the humidity and temperature as
> physical switches, the researchers can control when the bacteria grow and
> when the material stays dormant to serve structural functions.

So it can't get wet.

> they use light from the sun to grow and proliferate with very little
> exogenous material needed for their growth

Do the bacteria just die after the initial nutrients run out?

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g82918
To both comments, not really.

It can get wet, but just not too wet. And it doesn't necessarily die when the
initial nutrients run out as long as more naturally enter. The solution is to
deal with sub-maximal strength and provide a slow nutrient drip(or possible
occasional soaking with a nutrient slush).

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russfink
Sorry, maybe it's just me, but what is the main motivation for this? What
problems does it solve? What secondary problems does it create?

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loons2
> and concrete also releases CO2 when it cures.

As it cures, Portland cement ABSORBS "nearly a quarter" the CO2 used to
produce it.

[https://www.sciencemag.org/news/2016/11/cement-soaks-
greenho...](https://www.sciencemag.org/news/2016/11/cement-soaks-greenhouse-
gases)

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Gabriel_Martin
Similar but distinct from
[https://en.wikipedia.org/wiki/Microbiologically_induced_calc...](https://en.wikipedia.org/wiki/Microbiologically_induced_calcite_precipitation)

