
Ask HN: Does old concrete reveal information about air quality? - schoen
I noticed a worker at a demolition site using power tools to extract cylinders from an old concrete wall. While I&#x27;m sure this particular project isn&#x27;t aimed at scientific research, it made me wonder if there&#x27;s a demolition-materials equivalent of ice core research.<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Ice_core" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Ice_core</a><p>After all, steel has a different level of radioactivity depending on whether it was manufactured before 1945 (!).<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Low-background_steel" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Low-background_steel</a><p>Could there be similar properties in old concrete where one could learn interesting things about the composition of the nearby air at the time the concrete was first poured?
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mojomark
Interesting question. Air is wntrained in microscopic (or larger) cavities. I
would think the answer, as with anything, is "it depends". It depends on the
permeability of the particular concrete recipe and on a related note - the
thickness of the sample, how much air was entrained during production, as well
as the environmental conditions it's been exposed to (e.g. submerged
underground, underwater, or subjected to temperature fluctuations). For the
latter, I know that air voids can fill with water as entrained water expands,
which actually aids the self-healing properties of concrete, but I have no
idea if the air is compressed or dissolved (in the waster) or displaced out of
the concrete.

You may want to reach out to Dr. Tyler Let - a prof. with an surprisingly
addictive youtube channel [1] about concrete (yes, I know, but I feel I'm in
good company on HN).

Also, your question reminded me of an old article I read about researchers
analysing air from exumed lead coffins which were air tight. This isn't that
story [2], but it's similar.

1\.
[https://en.m.wikipedia.org/wiki/Mudskipper](https://en.m.wikipedia.org/wiki/Mudskipper)

2\. (PDF)
[https://www.google.com/url?sa=t&source=web&rct=j&url=https:/...](https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.hsmcdigshistory.org/pdf/Project-
Lead-
Coffins.pdf&ved=2ahUKEwju1Neay5LlAhUnhOAKHdXJDhkQFjAAegQIARAB&usg=AOvVaw0R5VAcd84aghQfhp-
GZOm0)

~~~
csours
Tyler Ley? [https://www.youtube.com/channel/UCrvfiHNDS_QI-
FgKQSmTITQ](https://www.youtube.com/channel/UCrvfiHNDS_QI-FgKQSmTITQ)

~~~
mojomark
Yup, thanks! I'm sick and on meds, so I'm going to blame that.

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refurb
Probably depends on what you want to measure.

Concrete is relatively porous to water and gas so things can leech out of it
and be deposited into it, confounding your measurements.

Concrete is also chemically reactive, a good example is corrosion caused by
salt. Whatever your trying to measure may chemically react with the concrete.

The only way to determine if it could be used is by running a few controls and
analyzing the samples.

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sitzkrieg
The problem with entrapped air content in PCC is initial mix and distresses -
faulting, cracking and spalling. The main concern of cracking, over the years
the porous bits that held air will all likely micro crack and equalize with
the atmosphere, as well as things like freeze/thaw and salting severely
affecting trapped air

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abeppu
Even if concrete held trapped air ... would we just learn that construction
sites for big concrete buildings have a lot of diesel-burning trucks and
equipment?

~~~
koheripbal
I think OP is thinking of ancient concrete/cement used by ancient cultures
such as the Romans.

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anfractuosity
Very interesting question!

Not directly related, but I found this -
[https://www.sciencedaily.com/releases/2017/07/170707211420.h...](https://www.sciencedaily.com/releases/2017/07/170707211420.htm)

"Even though producing concrete causes air pollution, concrete buildings in
urban areas can serve as a kind of sponge adsorbing sulfur dioxide to a high
level,"

Maybe the analysis they did and how they did it, might be interesting?

~~~
jradd
what formulae for concrete absorbs sulfur dioxide?

~~~
jradd
calcium silicate

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opwieurposiu
Concrete absorbs carbon from co2 in the air. If you were interested in co2
levels you might be able to deduce something from that.

I seem to recall that the biosphere 2 project had problems with the fresh
concrete absorbing too much co2 inside the sealed structure.

[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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smaslennikov
While water attracts everything around it and holds it nearby when frozen, I
don't believe concrete has similar characteristics. More knowledgeable HNers
will have a more thorough comments, I'm sure.

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Palomides
not on the inside, but you can estimate air pollution levels by amount of
lichen growth (if it isn't power-washed away, at least)

~~~
shawnz
Regarding OP's idea, are you saying it's been demonstrated to not be possible,
or just that it hasn't been demonstrated to be possible?

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jradd
pH balance of water and oxidization/electronegativity of the air could impact
the quality of concrete.

