BAUHAUS.INSIGHTS: StimuCrete – How Adaptable Can Concrete Be?
Long-lasting, robust, malleable – concrete is the 21st century’s most important building material. The original three-material system (cement, gravel, water) has become a high-performance material with properties that can be customised through the mix formulation. But there is one problem: Once concrete has been mixed, it can no longer be adapted. This means that unwanted changes in flow behaviour or durability—caused, for example, by varying environmental conditions or fluctuations in raw materials—can no longer be corrected.
The NanoMatFutur research group led by Jr. Prof. Dr. Luise Göbel is working on making concrete smarter. The idea: Newly developed additives will alter specific concrete properties only when activated by an external or internal stimulus. This would allow fresh concrete to be adjusted flexibly, essentially »at the push of a button«, or to equip new concrete structures with self-healing capabilities.
The Federal Ministry of Education and Research (BMBF) is providing the NanoMatFutur research group with nearly 1.9 million euros in funding until 2028
Mrs. Göbel, one approach of StimuCrete is to control the behaviour of fresh concrete, such as making it solidify on demand. How does this work, and what makes it particularly useful?
For solidification at the push of a button, we add very small magnetic particles to the concrete. If these substances are then activated by an externally applied magnetic field, they can move and align themselves along the magnetic field lines. This causes the concrete to solidify in a few short minutes.
At the moment, we are researching the potential of various raw material sources, including materials that are stored in landfill sites and by-products from industrial processes, to see whether they are suitable for this application. In this way, we can connect our research to the global push for sustainable building materials.
This on-demand solidification is particularly useful for additive manufacturing processes, such as 3D concrete printing, which require almost contradictory properties from fresh concrete: While the material should have a high viscosity during the pumping process, it should also ideally solidify immediately after being deposited from the print head, allowing it to be built up layer-by-layer.
Are there other property changes that StimuCrete can induce in fresh concrete?
Absolutely. And our research aims to expand the range of possibilities even further. For example, fresh concrete should not only be able to solidify on demand, but also to re-liquefy when needed. This could be interesting, for example, if concrete mixers are delayed in transit and the concrete is already starting to set. Our methods also increase sustainability as the amount of additives used during the manufacturing process can be reduced.
The second focus of StimuCrete is to make concrete structures more durable by endowing the concrete with self-healing properties. What does this mean, exactly? And what kind of damage can the concrete repair by itself?
The idea that concrete can repair itself to a certain extent is not new, and it’s an idea being pursues by research groups around the world. Our goal, however, is to develop additives in the form of capsules that react directly to potentially damaging substances. An example of this could be chlorides contained in de-icing salts. In this case, our new capsules would release salts on contact with chlorides, which would seal cracks in the concrete from the inside out. In this way, we could prevent the penetration of other substances that might cause the reinforcement to corrode and in turn jeopardising the stability of the structure.
Can StimuCrete be used anywhere, or is it limited to specific construction methods?
There are certainly some situations that are particularly well-suited. Self-healing concrete could be especially useful in underground garages, parking structures, and bridges. Concrete that changes its viscosity through external stimuli would likely be interesting for freshly poured concrete at construction sites or automated construction methods.
Your BMBF-funded research project began this January and ends in December 2028. How would you assess your progress so far, and what are the steps you’re looking forward to in 2025?
The biggest challenge we faced this year was finding appropriate team members for the NanoMatFutur research group. In the end, I was able to put together a great, motivated, interdisciplinary team who is passionate about researching our ideas. What’s special about this team is that it covers many different specialist areas, from electrotechnical issues to the experimental realisation of polymer syntheses. In the coming year, I’m most looking forward to diving even deeper into the subject matter. We have already been able to select suitable materials from our previous screenings, which we will now continue to research. Construction (materials) research requires a comprehensive characterisation of newly developed materials. After all, these materials are meant to be used in buildings that should last for longer than 80 or 100 years.
Do you see any possibilities for making concrete even more adaptable than what StimuCrete currently envisions—perhaps in a follow-up project?
I believe that with StimuCrete, as an intelligent building material of the future, we are already pursuing very ambitious goals. After the successful completion of our BMBF project, our first task will be to transfer the developed processes into practice. This will be a major challenge in the rather conservative construction industry and requires numerous tests and administrative processes. However, the industrial and research advisory board supporting our project has already confirmed the potential of our ideas, so I am optimistic.
Mrs.Göbel, these are exciting prospects and we will certainly be asking about this again. Thank you for the interesting interview.
The BAUHAUS.INSIGHTS questions on the »StimuCrete« project were asked by freelance editor Franz Löbling.