Swedish research paves the way for textile-reinforced concrete

By reinforcing concrete with textiles instead of steel, it is possible to use less material and create slender, lightweight structures with a significantly lower environmental impact. The technology to use carbon fibre textiles already exists, but it has been tricky to produce a basis for reliable calculations for complex and vaulted structures.

Researchers from Chalmers University of Technology in Sweden have now come up with a method that they say makes it easier to scale up analyses and thus facilitate the construction of more structures made of textile-reinforced concrete.

"A great deal of the concrete we use today has the function to act as a protective layer to prevent the steel reinforcement from corroding. If we can use textile reinforcement instead, we can reduce cement consumption and also use less concrete − and thus reduce the climate impact," said Karin Lundgren, who is professor in concrete structures at the Department of Architecture & Civil Engineering at Chalmers.

It is already well understood that using alternative binders in concrete instead of cement, such as clay or volcanic ash, it is possible to further reduce embedded carbon. But, so far, it is unclear how well such new binders can protect steel reinforcement in the long term.

"You could get away from the issue of corrosion protection by using carbon-fibres as reinforcement material instead of steel, because it doesn't need to be protected in the same way. You can also gain even more by optimising thin shell structures with a lower climate impact," said Prof Lundgren.

In a recently published study in the journal Construction & Building Materials*, Prof Lundgren and her colleagues describe a new modelling technique that was proved to be reliable in analyses describing how textile reinforcement interacts with concrete.

"What we have done is to develop a method that facilitates the calculation work of complex structures and reduces the need for testing of the load-bearing capacity," she said.

One area where textile reinforcement technology could significantly reduce the environmental impact is in the construction of arched floors. Since the majority of a building’s climate impact during production comes from the floor structures, it is an effective way to build more sustainably. A previous research study from the University of Cambridge shows that textile reinforcement can reduce carbon dioxide emissions by up to 65 percent compared to traditional solid floors.

Method that facilitates calculations

A textile reinforcement mesh consists of yarns, and each yarn consists of thousands of thin filaments (long continuous fibres). The reinforcement mesh is cast into concrete, and when the textile-reinforced concrete is loaded, the filaments slip both against the concrete and against each other inside the yarn. A textile yarn in concrete does not behave as a unit, which is important when you want to understand the composite material's ability to carry loads. The modelling technique developed by the Chalmers researchers describes these effects.

"You could describe it as the yarn consisting of an inner and an outer core, which is affected to varying degrees when the concrete is loaded. We developed a test and calculation method that describes this interaction. In experiments, we were able to show that our way of calculating is reliable enough even for complex structures," said the professor.

The work is now continuing to develop optimisation methods for larger structures.

*The article Textile reinforced concrete members subjected to tension, bending, and in-plane loads: Experimental study and numerical analyses is written by Adam Sciegaj, Sebastian Almfeldt, Fredrik Larsson and Karin Lundgren. At the time of the study, the authors were active at Chalmers University of Technology and Gdansk University of Technology in Poland.  The research projects that form the basis of the article are funded by the Swedish Research Council.

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