University Researchers Explore Cement Solidification in Space

A scanning electron microscope shows a 3 mm-thick sample of hydrated tricalcium-silicate, which is the main compound of ordinary Portland cement, with false-colored portlandite crystals sitting on top. Image courtesy of NASA and Penn State University (Juliana Neves and Peter Collins).

Researchers at Penn State University (University Park, Pennsylvania, USA) have collaborated with NASA on a project to study how cement reacts when it’s mixed with water in space. By investigating how cement behaves in microgravity environments, researchers hope to learn more about the complex solidification process that results in the formation of concrete.

The microstructural development of Portland cement, a basic ingredient of concrete, occurs in three phases: the addition of water to cement to create a cement paste; the transition between hardened phase and coarse aggregate; and the formation of the aggregate itself, otherwise known as concrete. During the transitional phase, elaborate combinations of crystalline structures grow inside the cement-based concrete. Various factors, including the reduction or absence of gravity, can impact the shape, volume, distribution, and overall development of these structures, as well as determine the properties of the concrete.

While there are still knowledge gaps when it comes to the microstructural development of concrete in terrestrial environments, the goal of the Penn State team is to examine this phenomenon in environments where there is little to no gravity present. “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,” said Aleksandra Radlińska, assistant professor of civil engineering at Penn State and the principal investigator of the concrete solidification project.

The project led by Radlińska was conducted in two phases. In the first phase, 120 pre-packaged samples containing cement and water in varying amounts were sent to NASA’s International Space Station (ISS) to be mixed together. Some of these packets also included alcohol to halt the hydration process for some cement samples. After these samples were tested and characterized by Penn State researchers, 28 additional samples were sent to ISS. In the second phase, cement and water were mixed as before, along with a centrifuge to simulate gravity levels on the Moon, Mars, and 0.7-g, thereby allowing researchers to determine differences in hydration reaction between the varying environments.

Penn State researchers believe that the information gleaned from their study will further our knowledge of cement as a building material both in space and on Earth. Moreover, the ramifications of this cement solidification project will not only be felt by present-day inhabitants of concrete structures but will have long-term consequences for future generations as well. “It is no longer a question of if we will need to colonize other planets, but a question of when,” Radlińska said. “Once we begin sending humans on missions to the Moon and Mars, we will have to provide them with safe environments to stay in for the duration of their mission.”

Source: Penn State News,