A concrete advantage for space explorers
European Space Agency astronaut Alexander Gerst works on the MICS experiment aboard the International Space Station. Observations of how cement reacts in space during the hardening process may help engineers better understand its microstructure and material properties, which could improve cement processing techniques on Earth and lead to the design of safe, lightweight space habitats. Credit: NASA

When humans go to the Moon or Mars to stay, they will need to construct safe places in which to live and work. The most widely used building material on Earth, concrete, may be the answer. It is strong and durable enough to provide protection from cosmic radiation and meteorites and it may be possible to make it using materials available on these celestial bodies.

Concrete is a mixture of sand, gravel and rocks glued together with a paste made of water and powder. While that sounds simple, the process is quite complex, and scientists still have questions about the chemistry and microscopic structures involved and how changes in gravity may affect the process.

A recent investigation on the International Space Station examined cement solidification in microgravity to help answer those questions. For the Microgravity Investigation of Cement Solidification (MICS) project, researchers mixed tricalcium silicate (Ca3SiO5 or C3S) and water outside of Earth’s gravity for the first time. The main mineral component of most commercially available cement, C3S controls many of its chemical reactions and properties. MICS explored whether solidifying cement in microgravity would result in unique microstructures and provided a first comparison of cement samples processed on the ground and in microgravity.

The investigators reported their results in a paper published in Frontiers in Materials, “Microgravity Effect on Microstructural Development of Tri-calcium Silicate (C3S) Paste.”

A concrete advantage for space explorers
These images compare cement pastes mixed in space (above) and on the ground (below). The sample from space shows more porosity, or open spaces in the material, which affects concrete strength. Crystals in the Earth sample also are more segregated. Credit: Penn State Materials Characterization Lab

“On missions to the Moon and Mars, humans and equipment will need to be protected from and radiation, and the only way to do that is by build