Carbon fiber has been the go-to manufacturing material in some industries for decades. One such industry is aerospace. If it were not for carbon fiber, the Boeing 787 wouldn’t exist. Yet despite its known benefits, carbon fiber hasn’t been as widely accepted in other industries – like architecture and building construction. Yet that might be about to change.
Just prior to the onset of the coronavirus pandemic, the foundation was poured for a brand-new building on the campus of Technical University Dresden in Germany. Though construction was temporarily halted, it is back on track. Builders are constructing a two-story educational building with a shell made entirely of carbon fiber reinforced concrete.
Engineers and researchers believe that carbon fiber is a better concrete reinforcement material than steel. They intend to prove as much with this building. If their design proves to be everything they say it will be, it could mean the end of steel-reinforced concrete in Europe and, eventually, everywhere else.
Lighter and Stronger
To understand what is going on in Dresden, let’s start with the basics. According to Rock West Composites out of Salt Lake City, Utah, carbon fiber is exponentially lighter than steel and yet still stronger. It offers equal or better tensile strength as well. Thus, carbon fiber reinforced concrete allows you to build a lighter building without sacrificing strength.
This matters in certain locations where the height of new buildings is limited due by the ability of the underlying soil to support them. A lighter building material allows for larger buildings on the same footprint. And still, that is not even the half of it.
Concrete and Dead Weight
According to Building Design and Construction senior editor John Caulfield, “at least half of the concrete in a typical building component is used to protect the steel reinforcement from corrosion.” In other words, the steel reinforces some of the concrete. But as much as 60% of the concrete serves no other purpose than to protect the steel from corrosion.
Caulfield refers to this as dead weight. He is absolutely right. If 60% of the concrete in a building serves no structural purpose – i.e., holding the building up – it is doing very little other than adding weight to the structure. Turning to carbon fiber as a reinforcement material solves that problem.
Carbon Fiber Doesn’t Rust
What you and I typically think of as carbon fiber is actually a carbon fiber reinforced plastic (CFRP). Manufacturers saturate carbon fiber fabric or tow with an epoxy resin that is then cured under high heat and pressure. The finished piece is a plastic product reinforced by the carbon fiber fabric within.
Why does this matter? Because carbon fiber reinforced plastics do not rust. This suggests a significant savings in concrete. If you don’t need all that extra concrete to protect the reinforcement material from rust, you can cut concrete volume significantly. This further reduces that undesirable dead weight.
Practically speaking, it is carbon fiber reinforced concrete that will make it possible for builders to top the Dresden building with a curved roof. The architects on the project referred to the roof as a ‘twist’. It sets on top of a concrete box. If you look at the picture, you can see that the roof twists and slopes downward toward the ground alongside the box.
The design would not be practical, let alone possible, using steel rebar. The roof would simply be too heavy. It would buckle under its own weight. With carbon fiber reinforced concrete though, all sorts of interesting designs are suddenly on the table. That is why this is so important.