Researchers Explore Cement Solidification in Space

This sample image from scanning electron microscopy (SEM) shows false-colored calcium hydroxide [Ca(OH)2] crystals atop hydrated tricalcium-silicate, which is the main compound of ordinary Portland cement. Image courtesy of Penn State University.

Researchers at Penn State University (University Park, Pennsylvania, USA) are collaborating with the U.S. National Aeronautics and Space Administration (NASA) (Washington, DC, USA) on a project to study how cement reacts when mixed with water in space.

According to the researchers, 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, combinations of crystalline structures grow inside the cement-based concrete. Various factors, including a reduction in gravity, can impact the shape, volume, distribution, and overall development, as well as determine the concrete’s properties. Many of these properties could influence the material’s resistance to corrosion.

While there are still knowledge gaps on the development of concrete in terrestrial environments, their goal is to examine this phenomenon in environments where there is little to no gravity. “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,” says Aleksandra Radlińska, assistant professor of civil engineering at Penn State and the project’s principal investigator.

The project 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 packets also included alcohol to halt the hydration process for some cement samples. The samples varied the type of cement, the type and number of additives, the amount of water, and the length of time until the hydration was stopped.

After these samples were tested and characterized, 28 additional samples were sent. In the second phase, cement and water were mixed as before, along with a centrifuge to simulate gravity levels on the Moon and Mars, thereby allowing researchers to determine differences in hydration reactions. The researchers believe the information gleaned from their study will further the knowledge of cement as a building material.

“It is no longer a question of if we will need to colonize other planets, but a question of when,” Radlińska says. “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.” Once the team better understands the hydration process, it plans to begin testing using materials indigenous to Mars. Though direct samples are hard to come by, the team says it recreated these materials based on the chemical composition of existing samples tested by Mars rovers. 

Source: Penn State University,