Our space ambitions have only one way to go – upwards – and this has brought scientists to the point where they have been thinking about building structures on other planets. As a part of this, many scientists have been looking at ways to build structures including houses in microgravity environments with one team at Penn State University exploring how cement solidifies in microgravity environments.
Researchers have long been studying the reaction of cement when it mixes with water here on Earth; however, there are still questions remaining and little is known about how this process plays out in space, where there is little to no gravity. The goal of this research is to better understand the complex process of cement solidification when gravity is taken out of the equation.
Having teamed with scientists at NASA, Penn State research decided to learn more about how cement reacts to microgravity environments in a two-phase study. In 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 separate 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.
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.