
Engineers Investigate a Simple, No-Bake Recipe to Make Bricks from Martian Soil - jameslk
http://ucsdnews.ucsd.edu/pressrelease/engineers_investigate_a_no_bake_recipe_to_make_bricks_from_martian_soil
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sillysaurus3
It would be really tempting to go settle Mars. Just... Leave everything
behind, and go.

I don't know why. Long-term survival seems unlikely for the first batch of
colonists. It's almost inevitable that there will be some sort of disaster.
And even if not, you'd have to live underground to avoid the radiation. Ever
want to go for a walk? Not so easy on mars. Surely you'd start to feel caged
after just a few weeks. Because you are.

And yet I can't get it out of my head how tempting it would be. Why? Is it
genetic? I've heard that one reason neanderthals died out is they would
migrate until running into an obstacle, like the ocean, and then settle there
on their perfectly-good land. The net result was that neanderthals stopped
expanding. Whereas we did things that didn't make sense: launch ourselves into
the sea, for example. And now we want to launch ourselves into the vast
nothingness of literally-nothing, to go live as moles in a confined area,
possibly without most of the amenities we take for granted.

Yet I think I would. I just wish I could figure out why.

Part of it is a longing for community. Life sometimes seems so pre-packaged.
It's an awesome life, to be sure, and in the society you're reading this
comment in, you probably have a lot of power to affect your life. You could
get rich. Or you could move to a new country, or decide what career you want.
But it's all been done before. And I think Mars is an escape hatch from that.
There, the frontier exists. Even if it's the life of a mole in a cage, it's a
cage nobody has ever dared to build before. And that's exciting.

~~~
amelius
If we wait a bit longer, we can send robots instead.

Also, I don't think we are compatible with a different gravitational constant.

~~~
zokier
Gravitational constant is the same everywhere. The hint is in the name,
"constant".

~~~
Gracana
Just like "spring constant," which is the same for all springs.

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pacaro
Some surprising materials have this property, including aspirin which can be
formed into tablets with no other ingredients.

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mparlane
Sounds similar to rammed earth construction?
[https://en.wikipedia.org/wiki/Rammed_earth](https://en.wikipedia.org/wiki/Rammed_earth)

~~~
mirimir
Yes, this is rammed earth. Styling it as a discovery seems strange. Also
strange:

> Researchers also investigated the bricks’ strengths and found that even
> without rebar, they are stronger than steel-reinforced concrete.

That's under compression, I'm sure.

~~~
peterwwillis
No! Flexural strength of 50MPa!!! And rammed earth only has a compressive
strength of 4.3MPa! Concrete has a flexural strength of around 30MPa, and I
don't know math so I don't know what the reinforced concrete is like, but this
is still stronger than even cooked bricks.

Here's the source publication:
[https://www.nature.com/articles/s41598-017-01157-w](https://www.nature.com/articles/s41598-017-01157-w)

It looks like because of the composition of the martian soil they figured this
would never work without a bonding agent and that it would require heating,
and then somebody tried it anyway, and it worked. But here's the neat
takeaway: The method they used to form it, along with particle size, and
whacking it versus slowly loading it, significantly strengthened the resulting
bricks. Nobody expected these things to happen, it seems.

From article:

 _" Loading rates were either quasi-static [..] or impact [..]. The lateral
boundary condition of compaction loading was either rigid (confined by a steel
wall), free, or flexible (confined by an elastomeric wall)"_

 _" Compacted Mars-1a solids were cut into beams and subjected to three-point
bending tests"_

 _" It is remarkable that the lateral boundary condition of compaction loading
significantly influences the strength and the shape of the compacted solid,
specifically, the thickness-to-diameter ratio. Compared with the boundary
condition, the effect of loading rate is secondary."_

 _" With the rigid boundary condition, the compacted Mars-1a samples are
structurally integral but the flexural strength is relatively low, comparable
with ordinary clay bricks. When the lateral boundary is free or flexible, R is
nearly 3 times higher than that of rigid boundary condition.

Between the free and flexible boundary conditions, the flexible boundary
condition reached high R at much lower Pmax and the resultant solid thickness
was only slightly smaller than that of the rigid boundary condition, much
larger than that of the free boundary condition. The strength-wise efficacy of
forming inside a flexible boundary is ~150–200% greater than the free boundary
for R ~30 MPa, taking into consideration the flexible boundary’s larger sample
sizes."_

\--

Concrete alone has a shitty tensile strength, compared to its compressive
strength. If you add steel cables to the concrete, the hybrid material's
tensile strength increases.

Similarly, Cod is what you get when you add natural fibers and other material
to rammed earth. Its tensile strength is also significantly higher due to the
addition of the fibers.

So then my next question is: could they bring along some cheap fibers (like
mylar?) to strengthen these Mars-1a bricks even more? Maybe the way the
materials are forming now, they don't need added tensile strength, or the
fibers could interrupt the formation somehow. But it's worth trying...

~~~
pjc50
This is making me wonder if it might be a viable/useful construction technique
on _Earth_ , depending on how hard it is to make the Martian soil simulant.

~~~
LoSboccacc
[https://en.wikipedia.org/wiki/Adobe](https://en.wikipedia.org/wiki/Adobe)
(mudbrick with straw as structural reinforcement) it already is, it was also
similarly used for reinforcing statue casts (with hairs iirc)

~~~
pjc50
If I've understood this correctly, Martian compressed soil is supposedly much
better than Adobe due to its iron nanoparticles?

~~~
LoSboccacc
yeah was more a general answer to the innovative process of mixing texture
with the mud

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endianswap
"The amount of pressure needed for a small sample is roughly the equivalent of
someone dropping 10-lb hammer from a height of one meter, Qiao said." On Earth
or with Mars's gravity?

~~~
averagewall
I initially thought that too but realized it was a meaningless concern.

Even if you knew g, it wouldn't help because the pressure also depends on the
thickness of soil it's landing on, as well as its mechanical properties - like
how much it's already been compressed. A hammer dropped onto concrete exerts
more pressure than it does dropped onto sand.

Also, what's the shape of the footprint of the hammer? Error in that will be
more than the difference between Earth and Mars gravity.

~~~
peterwwillis
See comments below for the link to their paper in Nature. Most relevant test
case is "Impact test, Flexible boundary condition", where they give all the
data on their test methodology.

If you load Supplementary Data, Figure S9[1], it shows 400MPa at 1ms. It also
shows (for the above test) around 9mm displacement at what looks like 365MPa?
I suck at math so I'll let someone else figure out the force.

[1] [https://static-
content.springer.com/esm/art%3A10.1038%2Fs415...](https://static-
content.springer.com/esm/art%3A10.1038%2Fs41598-017-01157-w/MediaObjects/41598_2017_1157_MOESM1_ESM.pdf)

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chiph
If they can make them into interlocking Lego-style blocks, creating cut &
cover tunnels is pretty easy.

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

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mod
You can do this on earth, with more pressure.

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

[http://www.dirtcheapbuilder.com/Home_Building/Earth_Block_Co...](http://www.dirtcheapbuilder.com/Home_Building/Earth_Block_Construction.htm)

~~~
peterwwillis
Neat! But fwiw, the Martian bricks are up to 50 times stronger :3

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cpete
Here's what The Onion, ahem, American voices have to say about it:
[http://www.theonion.com/americanvoices/scientists-
constructi...](http://www.theonion.com/americanvoices/scientists-constructing-
bricks-simulated-martian-s-55890)

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ahmeni
This seems like one of those things that you'd really want as a plan A but
absolutely require sensible plan B as a backup.

~~~
emilyfm
Plan A would be to send some robots to try building using this technique.

If it doesn't work, you're only out a few robots (who may be able to be
repurposed).

If it does work, leave them to it building a habitat which can be fitted out
by further waves of robots later. By time that's all done the hard part of
sending humans there will be more possible, and they'll have a base ready to
move into.

~~~
jsymolon
Wall-e unit for compressing blocks and leaving a heap.

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tantalor
> Digitally reconstructed brick

Huh?

