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http://www.theverge.com/2017/4/27/15436154/mars-soil-simulant-study-building-human-missions
Simulated Mars soil can be packed together into a solid brick-like material — without needing any added ingredients to hold it together. That might mean real Martian soil could be easily used as a tool for building structures like habitats on the Red Planet's surface, which could make human missions to Mars less complicated to pull off.
A group of engineers figured this out by using a high-pressure hammer to mash together material known as Mars soil simulant. It's a collection of rocks from Earth that have the same chemical makeup as the dirt found on Mars, as well as grains that are of a similar shape and size as Martian grains. After working with the material for a while, the engineers found that just adding the right amount of pressure was enough to form the soil into tiny, stiff blocks — stronger than steel-reinforced concrete.
[...] the researchers think there is some ingredient already in the Martian soil that helps it to stick together. They ultimately landed on iron oxide — a chemical compound that gives Martian soil its signature red color. When iron oxide is crushed, it can crack easily, forming fractures with very clean and flat surfaces, according to [Yu] Qiao [a structural engineer at University of California, San Diego, and the lead researcher on a NASA-funded study about this technique]. And when these surfaces are firmly pressed together, they form super strong bonds.
But these bricks aren't a complete solution to construction on Mars — at least not yet. The team only made miniature bricks, so it's possible that larger Martian bricks won't hold up so well. And it's not clear how durable they are either, which is important for a few reasons. Obviously, you don't want your structure to collapse. But less obviously, dust from the soil could break off into the air that astronauts are breathing, and inhaling large enough particles could cause health problems. The dust may also contain a type of salt known as perchlorate, which has been found throughout the Martian surface. Perchlorates can be toxic to human thyroid glands. So more research needs to be done to better understand these risks.
The full report is available: Direct Formation of Structural Components Using a Martian Soil Simulant, Scientific Reports 7, Article number: 1151 (2017) doi:10.1038/s41598-017-01157-w.
(Score: 3, Informative) by kaszz on Friday April 28 2017, @10:40PM (1 child)
It seems that martian soil contains nanoparticulate iron oxides and oxyhydroxides. This translates into a potential cell permeability and cytotoxicity risks! besides possible asbestos like risks. It should be kept outside any habitat in other words at all times.
The advantage from this compacting technique seems to be that it's more practical and efficient in application compared to other ISRU prototyping that utilizes high temperature or laser sintering.
To get the strength described, the sample which is cirka 1 x 6 cm is subjected to 400 MPa of pressure for circa 5-10 seconds. This then gives a flexural strength of circa 50 MPa. Given a gravity of 3.711 m/s² and a martian soil density of 1520 kg/m³ you could put 8864 meters of martian soil on Mars as a radiation protection. Figure 1B hints at 7 MPa instead which would translate into 1240 meter of soil on top of any habitat roof. The structural strength of a beam 2 meters long instead of 0.06 meters is perhaps way less. Anyone with an idea on how strong the material would be in larger sizes?
The method seems nice for building external protection etc. For interior habitat and structural beams etc. Heated material is perhaps way better. Just use a parabolic solar concentrator with ~430 W/m² input with a cloudless sky and no oxygen to make solid bricks. When the dust storms occurs the production just takes a pause and the parabola gets cleaned by the dust storms.
Maybe it's possible to create some kind of thermite from the magnesium oxide which is present at 7% weight in the soil? ie put blocks next to each other and fire it such that it creates a melted bond?
Materials present in the martian soil by weight percent from probes (circa!):
Na2O 2%
MgO 7%
Al2O3 9%
SiO2 4%
P2O5 0.5%
SO3 5%
Cl 0.5%
K2O 0.5%
CaO 5%
TiO2 1%
Cr2O3 0.3%
MnO 0.3%
FeO 1.5%
Ni 3%
Zn 2.5%
Br 0.25%
(Score: 2) by Dunbal on Saturday April 29 2017, @03:45AM
you could put 8864 meters of martian soil on Mars as a radiation protection. Figure 1B hints at 7 MPa instead which would translate into 1240 meter of soil on top of any habitat roof.
And that is why the rest of the world complains about America when it tries to use the metric system. Re-read what you wrote. Either your math is off (and I'm too lazy to check), you missed a decimal point somewhere, or you just didn't use SI units. I think if you're planning on piling 1km of material on your roof, you might as well have dug it underground...