Researchers are building the first bicycle bridge from flax

A consortium of about 15 European companies and universities has for the first time built a bridge made of composite material based on linen. It can be a green alternative to steel or reinforced concrete structures.

Humans have been cultivating flax for ten millennia for use in many applications, such as textiles, ropes, sheets, paper, and linseed oil. Now we can add composite materials to that list. Flax has strong fibers, grows quickly and does not need much fertilizer or water, all of which are properties that make the plant suitable as an organic building material.

The essence

  • Flax is a good biocomposite material thanks to its strong fibers and its qualities as an agricultural crop.
  • A European project team with two universities and two companies from our country used flax as raw material for a 15 meter long pedestrian and cyclist bridge.
  • The engineers believe that it will be possible to build bigger and stronger bridges in the future.

A multidisciplinary European team, in which two Belgian universities and two companies are also participating, recently came up with a surprising application: In the Dutch town of Almere, they built a bridge partly made of linen. The project is partly funded by the EU and has a budget of 6.9 million euros.

trucks



The engineers think that in the long run we will also build flax bridges that can carry the weight of cars and trucks.

Martin Prosler

Spokesman for the Smart Circular Bridge project

The 15 meter long bridge is intended for pedestrians and cyclists and can transport up to 275 people at a time. In the German city of Ulm and in the Dutch city of Bergen op Zoom, two more pedestrian and bicycle bridges will soon be built using the same technique. “The engineers believe that in the long run we will also build flax bridges that can carry the weight of cars and trucks,” says Martin Prösler, project spokesman.

‘In times of climate change and resource scarcity, biocomposites offer the construction sector, which has a large CO2footprint and consume a lot of resources, new opportunities. They have an enormous potential for a bio-based, circular economy, “say the participants in the project” Smart Circular Bridge “.

The project is said to be ‘circular’ because the designers have already prepared for the moment when the bridge comes to the end of its life. All parts can then be recycled mechanically, chemically or biologically. The bridge is also called ‘smart’ because it contains about a hundred sensors that will provide a wealth of information about the materials’ behavior and their aging process.

Resin

The building is not only made of linen. ‘The vegetable raw material amounts to 3.2 tonnes of a total weight of 9 tonnes’, says Prösler. The flax fibers are reinforced with a special bio-resin to form a light and stable material, with properties comparable to aluminum or light steel.

3.2 tons

proportion of flax

The flax in the bridge is good for 3.2 tons of a total weight of 9 tons.

The fibers, which are woven into mats, are impregnated with a polyester resin. In the first smart circular bridge, 25 percent of that resin is based on biomass’, it reads. In future bridges, engineers hope to increase that percentage to about 60 percent.

The bio-resin consists of waste from biodiesel production and recycled PET bottles and is one of the important innovations provided by the project. The resin is important for absorbing the remaining moisture from the flax fibers. Another innovation was the development of a cobalt-free ‘accelerator’, a substance that further improves the properties of the resin.

Four Belgian partners

Eindhoven University of Technology is leading the project, in which four other universities are involved, including KU Leuven and Vrije Universiteit Brussel (VUB). The latter two contributed to the testing of the bridge’s materials and control system, respectively. The construction of the bridge was carried out by the Dutch company FiberCore Europe, while the foundation was laid by Van Hattum and Blankevoort (also in the Netherlands).

Two Belgian companies also contributed: 24SEA and Com & Sens, like VUB, contributed to the bridge’s structural health monitoring system. Tens of thousands of bridges will have to be replaced in the EU in the coming years. In some cases, biomaterials such as flax may play a role.

‘These materials have a great future,’ says Professor Rijk Blok, project manager at Eindhoven University of Technology. According to his colleague Patrick Teuffel, future bridges will be able to handle larger spans and higher loads. Although we do not dare to predict when you will drive your car over a flax bridge for the first time.

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