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http://uahnews.uah.edu/read.asp?newsID=436]Link
IIRC, Mars is sulfur rich. Sulphur for you UK-ians.
This guy says you melt sulfur and use that instead of water as binder for concrete. I wonder if you could cast it around an inflatable mold, let it cure and then deflate the mold for re-use.
Give someone a sufficient [b][i]why[/i][/b] and they can endure just about any [b][i]how[/i][/b]
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I suspect that Mars would normally be perfect for the creation of concrete structures. And we dont really have to worry about using anything except modified standard concrete practices. The only problem would be too much iron in the mix.(we already use it to make reinforced concrete).
Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.
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Some where I have seen an article mixing concrete with glass to make it some what glow or appear translucent.
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As useful as concrete is, sulphur slowly "corrodes" to produce a sulphur dioxide. Hazardous if the colony needs clean air.
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Yup here is that stinky concrete.....
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For buried things that never get warmed, use water for your matrix around the rocks: make "icecrete". It won't sublime or warm up if buried deep enough. I honestly do not know if you can use salty water, but I would tend to doubt it, as the salt gets concentrated in the remaining brine as it freezes, up to the point of effectively precipitating-out as weak inclusions of salt in your material.
You still need rebar, though. Rebar must have a very much higher Young's modulus than the matrix, or else it will not share the load properly. Mineral fibers like basalt fiber will not have enough Young's modulus to make an effective rebar, whether your matrix is ice or cement. You will need mild carbon steel for this.
Your particulates come in two size distributions: "gravel" and "sand". Each needs to produced in angular, not rounded shapes, and each needs to pass at least a pair of sieves to obtain the correct distributions of sizes.
Down here, our sand can come from rivers, except we do not use rounded grains from quicksand. That's fine stuff, but it is definitely not windblown dust. We're talking roughly 0.2 to 0.5 mm sand grains, not 0.01 mm or less dust grains.
Our gravel is usually crushed stone, most commonly crushed limestone. Other species could serve, but this is not something you just pick up off the ground. This is mined blocks of stone crushed to shape and sieved to size. That size is around 10-20 mm. Maybe 30 mm at the largest, although larger is weaker concrete.
The matrix we use here is cement, made from finely-crushed limestone (a coarse powder) and cooked into very alkaline chemical reactivity. I have very serious doubts we could use that chemistry on Mars, as it doesn't even work here in the Arctic or the Antarctic. The water in it must stay liquid long enough to react fully with the cement. That takes about 30 days. It'll harden in a few hours, yes, but that's only about 20% of final strength.
If you use ice for the matrix instead, the "cure" time is very much shorter (being only how long it takes to freeze), and you can add fiber reinforcement to the particulate reinforcement. Fiber reinforcement does slow melting, but cannot stop it. On the other hand, you must prevent freezing (and low-pressure boiling) long enough to wet everything thoroughly, and further long enough to cast into the forms. Fiberglass scrap works pretty good for this.
Exposed liquid water at 0 C will boil and bubble anytime the vapor pressure of the water in the atmosphere above the liquid falls below 6 mbar. Not the total atmospheric pressure, but the vapor partial pressure of just the water. THAT is what the steam tables really say! Mars might as well be deep space. Atmospheric partial pressures of water vapor cannot exceed about 3 or 4% of the total atmospheric pressure, even at 0 C or higher. On Mars, total is about 6 mbar, and max water vapor pressure would be below about 0.2 mbar, even on a "warm" day above 0 C.
Whether you need rebar depends on the application. Things only loaded in compression can do without rebar. Things that experience shear forces, and especially things that experience tensile forces (as happens in bending), absolutely must have rebar! I think that would be as true for "icecrete" as it is for Earthly concrete. The ratio of rebar to matrix Young's moduli should exceed 10:1, and more is better.
Just some observations from a retired new product development engineer who has built a lot of different things.
GW
Last edited by GW Johnson (2016-07-10 14:05:11)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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