Using concrete for space colonies

During the first phase, the team sent 120 pre-packaged samples to the International Space Station (ISS), a working science lab in space. Sample packets included two or three separated compartments containing cement and water, or cement, water and alcohol (the latter was used to stop the hydration reaction at given time interval). While in orbit, an astronaut onboard the ISS was tasked with hydrating each sample by bursting the water packet into the cement packet and then halting the hydration at a given point using the alcohol for certain samples. This series of experiments varied the type of cement, the type of additives, the number of additives, the amount of water, and the length of time until the hydration was stopped. The samples were then returned to the Marshall Flight Center in Huntsville, Alabama and then transported to Penn State where they are currently being tested and characterized in detail.

During the second phase, the researchers sent 28 additional samples to the ISS. In this phase, the astronauts mixed the two-compartment samples as they did in the first phase but then used a centrifuge to simulate three gravity levels. These gravity levels included the Moon, Mars, and 0.7-g, which is in between the other two. This phase of the study will help the team determine the differences in the hydration reaction based on varying levels of gravity.

“All planets vary in their gravity levels,” Radlińska said. “Mars is only one third of the Earth’s gravity, but there is still some gravitational force.”

Once the results have been compiled, this research will be helpful in understanding how to use cement as a building material in space, but the knowledge gleaned will also be beneficial to improving Earth-based cement and concrete processing. Concrete is the single most widely used human-made material in the world, with global production reaching roughly 10 billion tons per year — and it has a carbon footprint to match. Even a slight improvement in the process could have huge implications on the sustainability of cement-based infrastructure.

“There is a lot of carbon dioxide emitted into the atmosphere during cement production,” said Radlińska. “The more we understand those early stages of hydration, which we don’t on Earth yet because it’s a very complex process, the more we can improve it.”

Once the team has a better understanding of the hydration process of traditional, portland-based cement, it would like to begin testing the process using materials indigenous to Mars. Though direct samples are hard to come by, the team can recreate these materials based on the chemical composition of existing samples tested by the Mars rovers.

“That’s why this research is so important,” said Radlińska. “Once we’ve run the research in space, we know the principles, and we can further test the materials on Earth. … The next stage of industrial development will be colonization of space and civil engineers will play a crucial role.”