Bridge made of high-tech materials and flax

While the vast majority of bridges are still built of steel and concrete or even timber, the search for new, more sustainable building materials begun a long time ago. A high-tech bridge made of flax, which was created in the Netherlands as part of the EU's "Smart Circular Bridge" project, is one example of innovative bridge construction. An interdisciplinary consortium consisting of 15 partners under the leadership of Eindhoven University of Technology is responsible for the first of a total of three planned structures to be built during the project.

Participants include five universities, seven companies, and three cities as well as architect, Assoc.-Prof. Hanaa Dahy who heads up the BioMat Department (Biobased Materials and Materials Cycles in Architecture) at the University of Stuttgart’s Institute of Building Structures and Structural Design (ITKE) and specializes in the use of bio-based materials in construction. She was also able to bring her expertise to bear on the high-tech bridge built using flax: "The project as a whole provides an important stimulus to show how alternative, biomass-based and annually renewable resources can be used in the construction industry,” Dahy explains: Our aim is to use these resources to overcome major challenges such as high CO2 emissions and high energy consumption in the production of construction materials."After all, traditional construction materials, such as concrete and metal, have a negative carbon footprint and are non-renewable. At the same time, the demand for construction materials continues to grow unabated. "Timber is not and should not be used to solve our construction materials shortage. Although it does grow back, it does so comparatively slowly,” says Dahy, “and we also need the forests to sequester CO2 in our struggle against climate change.” That is why the researchers directed their attention at raw materials that regenerate rapidly on a seasonal and annual basis, and in particular at one ancient and well-known plant: flax. 

Flax, a fibrous plant, combines several properties that are beneficial to the construction industry. When combined with a special bio-resin, it forms a lightweight and highly stable material, similar to fiberglass. It is also more sustainable to build with flax. This ancient cultivated plant is found throughout Europe, which eliminates the need for global transport routes and also grows much faster than, for example, a tree. However, the researchers are not focusing solely on the bridge construction, but are also asking themselves how the bridge construction materials could be recycled at the end 
of their service lives, whereby three options are currently being considered: chemical, mechanical, or biological recycling using fungi. Overall, the flax bridge is seen as a beacon of hope for the future of construction. Dahy says that even during her doctoral degree studies, she wondered why architecture up to that point had only been based on familiar materials such as glass, concrete, and metal. "Why,” she asked herself, “ isn't anyone researching the potential use of alternative materials?

The researchers are also relying heavily on modern technology in their search for new materials for use in future construction. "We are very fortunate to find ourselves in the digital era and to have digitalized planning, design and production processes at our disposal, which can help with prefabrication and construction." Digitalization and artificial 
intelligence are also enabling major advances in materials research. The bridge, for example, is being systematically monitored in real time as part of the project, with almost 100 sensors providing data on the material's behavior on a day-to-day basis to find out how the structure behaves when 200 people walk across it at the same time and what happens at different times of the year, during storms, or under the influence of hail, and snow or how the aging process of the material proceeds in detail.Some of the project partners have developed a structural health monitoring system, which uses optical fiber sensors installed in the bridge to provide information about deformations. Acceleration sensors detect even the finest vibrations caused, for example, by wind. The data is then analyzed with the help of artificial intelligence to identify patterns in the material's behavior. At the same time, engineers can use this data to refine their 
computational and material models, which will make it easier to develop the designs for future bridges and numerous other construction projects. 

A bridge built of flax will initially be erected in Ulm in the summer of 2023 as part of the project, which will be followed by the third and final bridge a year later, which will built in Bergen op Zoom in the Netherlands. Throughout this process, the researchers intend to take account of the data and findings already obtained from previous bridge constructions with a view to developing, a sustainable construction material, step by step.