Is it possible to make Asteroid Concrete?

Question

In the far future, man is trying to build a small colony in the asteroid belt - on one of the bigger asteroids. All the materials are to be mined from asteroids, and it is assumed the colony will have access to mine any and all types of asteroids as needed. The question is, can we make concrete solely out of minerals obtained from asteroids?

Concrete is aggregate, water, and dry cement.

Aggregate I presume can be broken down from any suitable asteroid. Some asteroids do have water in them, so water shouldn't be a problem either It's the cement part I'm having difficulty with. Some asteroids contain very tiny traces of Calcium in them, but would this be enough to make cement from?

Answer 1

The short of it is 'yes, asteroids contain the elements needed to make concrete.'

A typical asteroid contains Oxygen 36% Iron 26% Silicon 18% Magnesium 14% Aluminum 1.5% Nickel 1.4% Calcium 1.3%

And hydraulic cement is made from any of

Belite (2CaO·SiO2); Alite (3CaO·SiO2); Tricalcium aluminate (3CaO·Al2O3) (historically, and still occasionally, called 'celite'); Brownmillerite (4CaO·Al2O3·Fe2O3).

And there is overlap between what is needed and what is available.

The long of it is, just because the elements are there, does not mean they can be extracted and then combined into the necessary chemical form.

Cement is a binder, that binds aggregate into a solid structure. We use lime based cements and the above hydraulic cements, mainly because of their abundant availability and ease of extraction. Calcium, in fact, is widely available in the form of limestone throughout the world. But that is not to say that exotic cements could not be formulated using other elements.

The problem, I posit, will not be in the materials, but in the curing. Concrete does not dry, it cures. That is, it depends on oxygen in the atmosphere to complete the chemical reaction. Hydraulic cement depends on water. So building concrete structures in a vacuum presents a considerable challenge.

However, engineers HAVE considered using concrete as a building material on a space station using raw materials shipped up from the moon.

Answer 2

Not concrete. Pykrete.

Pykrete is a frozen composite material, originally made of approximately 14 percent sawdust or some other form of wood pulp (such as paper) and 86 percent ice by weight (6 to 1 by weight). During World War II, Geoffrey Pyke proposed it as a candidate material for a supersized aircraft carrier for the British Royal Navy. Pykrete features unusual properties, including a relatively slow melting rate due to its low thermal conductivity, as well as a vastly improved strength and toughness compared to ordinary ice. These physical properties can make the material comparable to concrete, as long as the material is kept frozen.

Out in the asteroids it is easy to find ice and other frozen stuff; methane clathrates, some CO2; all that good comet meat. And you have rocks.

To make space pykrete, melt the rocks and spin them into stone wool - long, thready, fibrous fluff. This should be a lot easier in lowG than it is down here - just rotate the melt gently and let centrifugal force to the work.
The stone wool will take the place of the wood. Around this fibrous framework now add your slurry of whatever ices you have and let them freeze back. As long as they are cold, they will hold their shape.

Space Pykrete would not be good for making beds and cabinets out of, but for structural applications in space this stuff should be excellent. One of the best Mythbusters involves a pykrete boat that they take out on the water. The main problem with real pykrete is that its favored temperature ranges do not overlap much with ours. In space staying cold should be less problematic.

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this concept inspired a little fiction vignette. WB does not like prose stories in the answer so it is on fictionpress. https://www.fictionpress.com/s/3334555/1/Pykrete-and-space-cats

Answer 3

The short answer would be "no"; Portland cement is essentially limestone (sedimentary calcium carbonate crystal) which is likely to be in short supply in an asteroid belt. Even if you had a substantial supply of material, the lack any substantial gravity would likely thwart such a plan. Building something in space that doesn't already have a somewhat rigid construction would be...difficult. You could perhaps pre-fab sections of it and put them into orbit, but that would be a planetary-based effort; essentially, a bricklaying operation, with the bricks coming from "elsewhere". Gryphon's suggestion might work with a variation - some sort of ground metallic powder that you could kind-of use a powerful energy source to quickly "flash-smelt" a kind of metallic foam, but you'd still have to have some sort of rigid mold or other constraining device.

Answer 4

https://en.m.wikipedia.org/wiki/Lunarcrete A basically identical rescipe to Lunarcrete is the way to go. Now a added bonus is to add urea (you throw it out anyways when you recycle urine) and you get a concrete that sets stronger then modern concrete and grows stronger as it ages (a example of concrete using urea would be Roman concrete) Here's a article I read not too long ago on the subject: https://www.google.com/amp/s/www.bbc.com/news/amp/world-africa-45978942

Note: Urea needs sunlight to start its chemical reaction