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Filigree structures: Using concrete efficiently with 3D printing.
Is this what the bridge of the future will look like? Visualisation: Yinan Xiao, Noor Khader – ITE/Braunschweig, design: Pierluigi D’Acunto, Ole Ohlbrock – ETH Zurich.

Concrete consists of cement, water and different aggregates. It is cheap, available in large quantities, easy to process and durable. Reasons enough why no other material is used so frequently worldwide. Nevertheless, concrete has a problem: according to the International Energy Agency (IEA), the construction and building sector is responsible for around 40% of global greenhouse gas emissions. Concrete production alone is responsible for around 8% of global carbon dioxide emissions and releases more CO2 than the entire transport sector. In order to reduce the environmental impact of concrete, scientists at the Technical University of Braunschweig are researching how the immense material consumption in construction can be reduced.

To reduce material requirements, energy consumption and waste, the researchers are using additive manufacturing processes such as 3D printing. By only placing concrete in the component where it is actually needed, they say, 50 to 70% of material can be saved. According to a TU press release, the Institute for Building Materials, Solid Construction and Fire Protection (iBMB) and the Institute for Structural Design (ITE) are going one step further. In the project Beyond 3D Printing – A novel spatial printing technology for lightweight spaceframe concrete structures, funded by the Volkswagen Foundation, the researchers led by professors Dirk Lowke, Harald Kloft and Norman Hack are developing a 3D injection printing process (Injection 3D Concrete Printing) to produce lightweight spatial structures. “In concrete construction in particular, it is common to have solid concrete walls. However, we want to achieve a light, dissolved construction method that is more familiar from wood or steel,” explains Professor Lowke.

In the process, a concrete strand is injected into a carrier medium. The difficulty: The carrier fluid must be perfectly matched to the concrete and the robotically controlled process to keep the material in the desired position. Rock powder suspension looks like a mud pack and forms a grid-like structure when drained. “The concrete components are suitable for bridges or roof support structures, for example,” he said. The parts are to be manufactured in the factory and assembled on site. “Besides the CO2 saving potential, we can also create new possibilities in architecture with our process, namely complex geometries without spatial restrictions.” The project team is also researching the integration of reinforcement so that the structure is as load-bearing as possible.

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