Engineers investigate a simple, no-bake recipe to make bricks from Martian soil

April 27, 2017
A brick made of Martian soil simulant compacted under pressure. The brick was made without any additional ingredients and without baking. Credit: Jacobs School of Engineering/UC San Diego

Explorers planning to settle on Mars might be able to turn the planet's red soil into bricks without needing to use an oven or additional ingredients. Instead, they would just need to apply pressure to compact the soil—the equivalent of a blow from a hammer.

These are the findings of a study published in Scientific Reports on April 27, 2017. The study was authored by a team of engineers at the University of California San Diego and funded by NASA. The research is all the more important since Congress passed a bill, signed by President Donald Trump in March 2017, directing NASA to send a on Mars in 2033.

"The people who will go to Mars will be incredibly brave. They will be pioneers. And I would be honored to be their brick maker," said Yu Qiao, a professor of structural engineering at UC San Diego and the study's lead author.

Proposals to use Martian soil to build habitats for manned missions on the planet are not new. But this is the first that shows astronauts would need minimal resources to do so. Previous plans included nuclear-powered brick kilns or using complex chemistry to turn organic compounds found on Mars into binding polymers.

In fact, the UC San Diego engineers were initially trying to cut down on the amount of polymers required to shape Martian soil into bricks, and accidently discovered that none was needed. To make bricks out of Mars soil simulant, without additives and without heating or baking the material, two steps were key. One was to enclose the simulant in a flexible container, in this case a rubber tube. The other was to compact the simulant at a high enough pressure. 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.

Researchers investigated the bricks' strengths and found that even without rebar, they are stronger than steel-reinforced concrete. Here is a sample after testing to the point of failure. Credit: Jacobs School of Engineering/UC San Diego

The process produces small round soil pallets that are about an inch tall and can then be cut into brick shapes. The engineers believe that the iron oxide, which gives Martian soil its signature reddish hue, acts as a binding agent. They investigated the simulant's structure with various scanning tools and found that the tiny iron particles coat the simulant's bigger rocky basalt particles. The iron particles have clean, flat facets that easily bind to one another under pressure.

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

Researchers said their method may be compatible with additive manufacturing. To build up a structure, astronauts could lay down a layer of , compact it, then lay down an additional layer and compact that, and so on.

The logical next step for the research would be to increase the size of the .

Researchers compacted Mars simulant under pressure in a cylindrical, flexible rubber tube. This is what the result of the experiment looked like before it was cut into bricks. Credit: Jacobs School of Engineering/UC San Diego

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Eikka
not rated yet Apr 27, 2017
the equivalent of a blow from a hammer.


Not too fast. Many don't appreciate, but a simple hammer blow can deliver ten tons of pressure. Not so little if you need to sustain it for more than the millisecond it takes for the hammer to bounce.

EmceeSquared
1 / 5 (2) Apr 27, 2017
If the landing craft could deliver the necessary blow to spank these bricks out of the Martian soil, making them wouldn't require an additional energy source (and the additional machinery to store/deliver it). Maybe the main craft orbits Mars a while as small machines land to prepare the soil for impact, then the main craft slams into the "brickyard". Which might also provide a shock absorber for a softer landing less destructive to the craft.
dnatwork
not rated yet Apr 27, 2017
the equivalent of a blow from a hammer.


Not too fast. Many don't appreciate, but a simple hammer blow can deliver ten tons of pressure. Not so little if you need to sustain it for more than the millisecond it takes for the hammer to bounce.



Fair enough, but pressure is force per unit area. A small robot could apply ten tons of pressure to small areas for a long time. Send a few 3D printers on wheels to Mars ten years before the astronauts, and you could have a whole town built.
danR
4 / 5 (1) Apr 27, 2017
"The engineers believe that the iron oxide, which gives Martian soil its signature reddish hue, acts as a binding agent. They investigated the simulant's structure with various scanning tools and found that the tiny iron particles coat the simulant's bigger rocky basalt particles. The iron particles have clean, flat facets that easily bind to one another under pressure."

IRON particles? Surprisingly, this comes from the engineering school itself. On Mars, there is no free iron.
ronshere
5 / 5 (2) Apr 28, 2017
This happens to be one of the earliest building techniques known as Rammed Earth. It has been widely used for centuries and is hardly new or their 'discovery'.
ddaye
not rated yet Apr 28, 2017
There's no mention of atmosphere. In a vacuum some materials including metals can bond just from contact, to a greater extent than we see within the oxygen atmosphere of earth. Were these tests done in a simulated low pressure no-oxygen Martian atmosphere?

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