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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?

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  • $\begingroup$ Why would you need to use cement? Metal isn't exactly in short supply on asteroids, and it's stronger and more airtight than concrete. $\endgroup$ – Gryphon Feb 15 at 16:35
  • $\begingroup$ If you must have concrete, then some form of geopolymer cement may be more easily made with raw materials available on a common or garden asteroid. And concrete does not contain "dry cement"; when the concrete is made the cement is surely wet, and after it sets it is no longer cement. $\endgroup$ – AlexP Feb 15 at 16:37
  • $\begingroup$ You're not going to build structures like Earth and you don't need the same qualities as concrete has. You'll most likely tunnel and seal the resulting tunnel system with airtight materials (far into the future, that could/would be something beyond our current understanding of materials science and engineering. $\endgroup$ – StephenG Feb 15 at 19:45
  • $\begingroup$ I removed [space] as a tag because I needed to make room for [asteroids]. It seemed like the best choice. But feel free to fix it if you don't like my choices. $\endgroup$ – Cyn Feb 15 at 23:34
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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.

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  • $\begingroup$ This answer is bountyworthy. It is for answers lime this that I come here :) $\endgroup$ – Renan Feb 15 at 23:38
  • $\begingroup$ I've understood that is possible to make concrete without water with sulfurous rich regolith. But I need citation for that. $\endgroup$ – Ender Look Feb 16 at 0:50
  • $\begingroup$ @Ender Look My research on sulfurous concrete before I posted my answer indicated that it requires a particular 'atmosphere' and environment, and would not be viable on an asteroid. ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080022947.pdf $\endgroup$ – Justin Thyme Feb 16 at 15:53
  • $\begingroup$ Oh, I didn't know that $\endgroup$ – Ender Look Feb 16 at 16:08
  • $\begingroup$ Also note that the oxygen/curing requirement was the reason that the Biosphere 2 experiment experienced oxygen losses which would have killed the researchers if the decision to admit extra oxygen to the "sealed" environment had not been taken. $\endgroup$ – WhatRoughBeast Feb 18 at 18:41
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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.


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

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  • $\begingroup$ Pykrete would, indeed, be a good candidate for infrastructure on the surface of the asteroid. I am thinking structural bases for antennae, pylons for beacons, roads, and such. However, sublimation in a vacuum could be a problem. With no atmosphere, there would be minimal vapor pressure. That is the same problem with sulfur concrete. It would probably have to be coated with something. $\endgroup$ – Justin Thyme Feb 16 at 16:37
  • $\begingroup$ @Willk in my stuffens I tend to use Pykrete for interiors and apartments. It's a nice substitute for wood. $\endgroup$ – Celestial Dragon Emperor Feb 16 at 18:44
  • $\begingroup$ @CelestialDragonEmperor - Google did not help me with Stuffens, except for Doc Mc. What are they? $\endgroup$ – Willk Feb 17 at 3:07
  • $\begingroup$ @JustinThyme - I read somewhere that sublimation becomes an issue for ice bodies only at a certain proximity to the sun. That is how comets can persist - they only sublimate off their material when they get close in here with us and the rest of the time they don't. But if you were close enough that sublimation was an issue you could cover it with reflective foil or spray on a layer of coating. $\endgroup$ – Willk Feb 17 at 3:13
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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.

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  • $\begingroup$ And I misread the question, of course. Still, finding the right kind type of calcium carbonate in what we know as asteroids would still be a task. $\endgroup$ – Mike Given Feb 15 at 22:28
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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

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