NASA researches examined cement solidification in microgravity to help answer questions about how concrete could be used in space, for instance to build on Mars or the Moon.
Concrete is the most widely used building material on Earth, and there are reasons to believe it may be the same in space. Concrete 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 Mars or the Moon.
Concrete consists of a mixture of sand, gravel, and rocks, glued together with a paste of water and cement powder. But while we understand (for the most part) how concrete works on Earth, doesn’t mean it works the same under different gravitational forces.
To find out how concrete may behave in space, the NASA researchers mixed tricalcium silicate (C3S), the main mineral component of most commercially available cement, and water outside of Earth’s gravity. The aim of the research was to find out whether solidifying cement in microgravity would result in unique microstructures.
The team created a series of mixtures that varied the type of cement powder, number and type of additives, amount of water and time allowed for hydration. As the grains of cement powder dissolve in water, their molecular structure changes. Crystals form throughout the mixture and interlock with one another.
The mixtures were tested at a space station, which has an on-board centrifuge that can simulate gravity levels of the Moon and Mars, something not possible on Earth.
Turns out, the gravitational forces do have an influence on concrete. At the space station, the samples showed considerable changes in the cement microstructure compared to those processed on Earth. One of the main differences was increased porosity, which has a direct bearing on the strength of the material.
So while the samples did solidify, meaning we could theoretically build with it in space, the resulting concrete still has to be tested for its strength.
Photos: NASA / Penn State Materials Characterization Lab