As cement hardens through a process called hydration, the molecules within the mixture develop millions of microscopic crystals, like those seen in this screenshot from the NASA video below. These interlocking crystals help the cement molecules bind with each other, as well as other concrete ingredients like gravel, sand, and small rocks.
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.
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