Astronauts mix cement on ISS for the first time

With this researchers have taken a small step toward building structures on other worlds, such as the Moon and Mars

Photo: NASA ScienceCasts A comparison between cement allowed to harden for 56 days in regular gravity on Earth (left) and microgravity on the ISS (right)

Concrete, in one form or another, has been a staple of human construction for some 5,000 years. Now, researchers have finally brought the ancient technology to outer space. For the first time, scientists have successfully mixed cement - a primary ingredient of concrete - in the microgravity environment aboard the International Space Station (ISS).

As part of an experiment called the Microgravity Investigation of Cement Solidification, researchers sent the basic building blocks of cement - tricalcium silicate, hydrated lime, and distilled water - to the ISS. The ingredients were then mixed in pouches and allowed to harden for 42 days through a process called hydration.

Interestingly enough, compared to ground-mixed cement, space-mixed cement is more uniform in density (which makes it stronger), but it's also more porous (which makes it weaker). Thus, because of the opposite effects occurring concurrently, the research team will need to destroy the samples later in 2019, after concluding their microstructural analysis. This will let them determine whether uniformity or porosity plays a bigger role in the cement's overall strength.

Because the new research is the first to compare cement mixed in space to a control batch mixed on Earth, it opens the door to developing better ways to manufacture the substance in various gravitational environments. And if humans are to build a Moon Village or a martian colony in the years to come, we'll likely need to master mixing cement on other worlds.

"On missions to the Moon and Mars, humans and equipment will need to be protected from extreme temperatures and radiation, and the only way to do that is by building infrastructures on these extraterrestrial environments," says study author Aleksandra Radlinska. "One idea is building with a concrete-like material in space. Concrete is very sturdy and provides better protection than many materials."

We confirmed the hypothesis that this can be done," says Radlinksa. "Now we can take next steps to find binders that are specific for space and for variable levels of gravity, from zero [gravity] to Mars [gravity] and in between."

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