Recently there was news that the first public building in Germany was opening in Dresden Carbonbeton arises. A sports hall. What is carbon concrete?
This is a concrete in which carbon fiber materials are used as reinforcement instead of steel rods. Do you know what reinforced concrete looks like?
Not really.
Reinforced concrete is a relatively old story. It was originally called reinforced concrete and was introduced by a Frenchman in the 19th century. Monier was the man’s name (pronounced: Monjé). I pondered for a long time why reinforcements in reinforced concrete were always referred to as monier iron, with “ie”. Now I know: That’s because people couldn’t pronounce the name correctly. However. In any case, you have steel rods or grids and, at some distance, formwork made of wooden panels, for example, and the concrete is then poured into them. Concrete is quite strong. One of the oldest known concrete buildings is the Pantheon in Rome. The ancient Romans built it and it is still standing, although it has had to deal with earthquakes from time to time. However, the concrete itself does not have much tensile strength.
What does that mean?
If you bend an unreinforced concrete slab a lot, it will simply break. Steel, on the other hand, has high tensile strength and can absorb the stress when bending. But it has two well-known disadvantages: it is heavy and it can rust. And since in many reinforced concrete buildings the load eventually leads to cracks through which water penetrates, often mixed with de-icing salts in the case of roads, corrosion occurs on the steel – and at some point the structure is no longer load-bearing. We just experienced that in Berlin with the Elsenbrücke at Treptower Park. It was built from prestressed concrete during the GDR era. Back then, no one expected the heavy goods traffic and the traffic density that we have had since the fall of the Wall. In general, the lifespan of concrete buildings is nowhere near as long as initially assumed. Some don’t even last as long as their creators live.
Dr. Schmidt explains the world
Stephanie Schoell
As a polymath of the nd editorial team, the science journalist Dr. Steffen Schmidt has an answer to almost every question – and if he doesn’t, he answers another one. All episodes can be listened to on: dasnd.de/schmidt
Okay, but what can carbon concrete do that reinforced concrete cannot?
It’s much lighter, and carbon fiber doesn’t rust. But the material is comparatively expensive. The carbon fibers do not need such a thick protective layer to protect them from rust because there is none. This has a big advantage in terms of wall thickness, except in terms of sound insulation. The first applications were renovations of existing buildings.
The material is not only interesting for new buildings.
Several bridges in Germany have been renovated using carbon concrete. Second point that will be of more interest to architects: With the relatively flexible carbon fiber mats, you can build structures that would be much more complex with reinforced concrete. This could be interesting in the medium term for 3D printing of houses, because there have been problems incorporating reinforcement during printing. But that is a thing of the future.
You said the material was very expensive. How do you even get carbon fiber?
Carbon fiber is made by carbonizing carbon-containing fiber materials, a bit like making coke.
Is that environmentally friendly?
Nope. Carbon fibers could be virtually climate-neutral if suitable natural fibers were used. Or if one were to use the adhesive from wood, lignin, which is currently a waste material in paper production. But this is not yet ready for industry. It is more environmentally friendly in that you need much less cement. In construction, the greatest damage to the climate comes from the production of cement and brick as building materials.
Has there been research into this for a long time?
Quite a while now. It is a branch of the textile concrete development. Dresden and Aachen are world leaders in this regard. There were probably some difficulties in developing suitable approval procedures for construction law.
Because there were no standards for it yet?
Exactly. It started that way with concrete too. The Victoriastadt in Lichtenberg, which is named after the English Queen Victoria, was originally built from concrete, which was then called English concrete. And experimentally. At that time this part belonged to Rummelsburg and not to Berlin. So the Berlin building regulations did not apply. This newfangled building material would not have been allowed for entire houses within Berlin. They then tried it out outside the city gates.