In Germany, researchers at the TU Braunschweig are working on the development of a new, specific 3D printing process. Instead of currently available technologies, they are instead using syringes to design more complex shapes. To do this, the researchers inject a fine-grained concrete into a non-hardening carrier liquid (more precisely a suspension of crushed limestone). The latter acts as a matrix that supports the structure; 3D injection concrete printing could introduce such complicated constructions that would otherwise not be producible.
When we think of 3D concrete printing, we often think of extrusion: a robotic arm deposits successive layers of material until the final structure is created. This is the most widely used method to date. However, some players are interested in 3D injected concrete printing, which is the process of injecting a liquid material into another material with certain properties. The first material is kept stable in the second, which allows users to create more complex structures. For example, the French start-up Soliquid, which has developed a process for printing concrete parts in a gel matrix. One of the co-founders, Amaury Thomas, is a co-author of this study.
In their work they explain that Injection 3D Concrete Printing (I3DCP) can be divided into three categories: Injection of a fine-grained concrete into a non-hardening carrier liquid; Injection of a non-hardening suspension into a fine-grained concrete; Injection of a fine-grained concrete with certain properties into concrete with different properties. The team chose the first category and therefore injected their material into a liquid, in this case ground limestone.
In the article, the researchers added: “To better understand the underlying physical mechanisms, we are conducting experiments that vary the rheological properties of the carrier fluid, the concrete flow rate and the nozzle displacement velocity. In this study, we use a ground limestone suspension as the carrier fluid. We investigate the influence of the rheological properties of the carrier fluid on the positional stability of the injected concrete in small-scale compression tests. Based on this, we develop an analytical model that describes the positional stability as a function of the rheological properties. “
As the pictures show, the structures printed in 3D using this process appear to be formally more complex: Instead of a block of material, there are concrete strands that interlock. This method could be used in particular in the aerospace industry to imagine innovative lightweight structures for space. At least that’s what the researchers are aiming for – you can find their entire study HERE.
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