In early February 2022, German ESA astronaut Matthias Maurer tested how freshly poured concrete behaves under conditions of zero gravity on the International Space Station (ISS), and how this can contribute to environmental protection. The experiment ‘MASON / Concrete Hardening’ is a joint project of the German Aerospace Center (DLR), the University of Cologne, and the University of Duisburg-Essen.

Global CO₂ emissions amount to around 38 gigatons (38,000,000,000 tons). Of this figure, three gigatons are produced in the manufacture of cement alone. Cement, in turn, is the essential component of concrete, currently the most important building material. Optimizing its use by means of better processes could contribute to reducing its carbon footprint.

‘The material concrete has been used by humans for thousands of years, and yet still holds riddles for us. We want to clarify some of these questions together with Matthias Maurer on the ISS,’ said Professor Dr Matthias Sperl at the DLR Institute for Materials Physics in Space.

Why concrete experiments on the ISS?

Concrete is not a material easily associated with space travel. However, research on board of the ISS can be conducted under conditions of prolonged weightlessness, providing insights into the behaviour of materials that are only possible to a very limited extent in terrestrial laboratories.

In addition to the mixing ratio and reinforcements (armouring), the curing of the material is decisive for the strength of concrete. The setting process determines the arrangement of the components inside the concrete as well as the distribution of trapped air bubbles.

On Earth, curing is strongly influenced by gravity. For materials research, it is therefore of great interest to investigate how this mixture of sintered lime and clay plus sand and water behaves without this influence. ‘In the computer tomography images, you can see at first glance that the samples from Earth differ from those from the ISS due to the different distribution of air bubbles and pores,’ said Dr Karsten Tell from the University of Cologne’s Institute for Theoretical Physics. The new findings allow the researchers to better understand chemical and physical processes, and can be used to optimize mixing ratios, which ultimately save valuable resources.

Concrete’s solidification and drying process can take weeks and months. That is why research on the International Space Station is so important – only here can the same conditions of zero gravity (G) be permanently achieved.

The data obtained during Matthias Maurer’s experiments also provide the basis and reference values for further experiments in terrestrial laboratories. Here, artificial weightlessness is created for shorter periods of time in so-called ‘clinostats’.

‘If we succeed in simulating weightlessness, a large number of experiments could be carried out more quickly, easily and cheaply in the future,’ Professor Dr Martina Schnellenbach-Held of the University of Duisburg-Essen’s Institute of Solid Construction (IfM) remarked. She and her team made the experiment possible by developing a special concrete mixer that meets the strict safety precautions for the ISS: a hand-sized mixer that is operated manually.

How to build on the Moon and Mars

‘MASON’ (Materials Research in Microgravity on Concrete) has a cosmic component as well as terrestrial applications. If humanity realizes its plans to establish a permanent settlement on the Moon or Mars, the stations must be built of solid material, primarily to protect them from small meteorites and cosmic radiation.

The formulae used for construction projects on Earth to calculate the statics of buildings always assume the Earth’s gravitational force of 1 G. On the Moon, however, gravity is one-sixth less. It is not certain that a simple conversion would result in a stable construction. Therefore, the data obtained within the framework of ‘MASON’ are literally an important building block.

On the Moon and Mars, essential components of concrete are not available, so astronaut Maurer is also conducting experiments on samples made of artificially produced lunar dust.

Partnerships and funding

The German Space Agency at DLR supports the scientific work at the University of Cologne and the University of Duisburg-Essen with funding from the Federal Ministry of Economics and Climate Protection (BMWK).

Media contact:
Dr. Karsten Tell
Institute for Theoretical Physics
University of Cologne
+49 220 3601 1006
karsten.telluni-koeln.de

Press and Communications Team:
Jan Voelkel
+49 221 470 2356
j.voelkelverw.uni-koeln.de

More information / video:
https://youtu.be/J2kL--y6ftk