Can astronauts make cement out of waste?

Future astronauts could make lunar buildings out of moon dust and urine; That’s the suggestion of chemists, who made a cement from urea, a major component of urine, and fake lunar soil.

When humans establish long-term residence on other planets or on the moon, they will need to pack light, in part because shipping materials from Earth is expensive; NASA has estimated that each pound of material sent into Earth orbit costs about $10,000. Harnessing local resources could keep costs down – researchers have suggested using lunar soil to make concrete or cement to 3D-print housing for astronauts – but most cement mixes require a lot of water, which is in short supply on the moon and terribly heavy to fly into space.

On Earth, adding a chemical called a superplasticizer to a cement mix reduces the amount of water needed by keeping a drier mix from crumbling too much, while leaving it flexible enough to be used in a 3D printer, but most of the superplasticizers are organic compounds, also scarce on the moon.

Urea breaks the hydrogen bonds between molecules, which reduces friction and allows the molecules to slide past each other more easily. A powder of silica and aluminum oxide, a substitute for moon dust, is the main ingredient in the scientists’ cement, its chemical content is similar to that of fly ash, a main component of common cement mixes, but with larger grains. and crystalline. The team mixed that powder with powdered urea purchased from a chemical supply company, not distilled from actual urine, along with a little water to make the cement; Compared to two other superplasticizers used in construction on Earth, urea performed very well, researchers say.

The mix held its shape under light weight and withstood temperature changes, extruding the cement through a tube and stacking several layers on top of each other using a 3D printer made a tiny, stable wall, they reported. It is planned to test the cement in more extreme temperatures and in a vacuum chamber that mimics the moon’s lack of atmosphere; then the next step would be to scale the wall to a more realistic size, they also want to investigate if future astronauts would have to purify their urine or if they could use urine on the cement directly.