Nov 10, 2016 | By Alec

So why aren’t we all living in 3D printed homes yet? When you see 3D printed concrete creations, such as this 3D printed pavilion by students from TU Eindhoven, it looks like a future that is almost within reach. Not only can concrete 3D printing provide architects with immense design freedom, it can also greatly reduce labor costs – making homes more affordable for everyone. German inventor Kai Parthy, known as the filament wizard, is now working on a clever addition that should make this process even more streamlined and automated: scalable BMSF (bionic-mesh-steel-fiber) reinforcement inserts.

It’s a solution for one of the problems that is preventing 3D printing from taking over the construction industry, and goes right to the heart of concrete itself. For ‘pure’ concrete is not as strongly as we always think it is, with much of the strength coming from reinforcing steel rebar rods. This problem is the same when pouring concrete and 3D printing it. In fact, when 3D printing homes (which WinSun has been pioneering with great success) the concrete 3D printing process is almost continuously stopped to make it possible to insert reinforcing steel rebar rods in all load-bearing sections. Without it, the concrete would tear and break even under small loads. But it also means that the 3D printing process is in no way as automated as it could be.

This is where Kai comes in. Of course we know him especially for his fantastic filament creations, and the title of filament wizard is definitely deserved. In his Among his earlier creations, you can find materials such as the LayWoo-D3 wood filament, the flexible BENDLAY flex filament, the wax-like MOLDLAY and even the sponge-like LAYFOMM. Kai also pioneered the shoe sole mimicking SOLAY filament and earlier this year unveiled his LAY-AWAY series of soluble support filaments, which ensure that support is always perfectly removed without damaging the main print.

But Kai is also an all-round inventor, and just unveiled his pioneering solution for concrete 3D printing. In a nutshell, his BMSF inserts are highly flexible steel support structures that can be used throughout any (3D printed) concrete structure, can be automatically inserted and can be scaled into any shape and form. You could call it the next generation of rebar inserts, and a very cost-effective one.

As Kai explained, his solution actually builds on decades of construction efforts to make concrete more suitable for different applications. “The development of fiber concrete has been a priority for decades. Elongated fibers, made of steel or, more recently, of plastics. Unfortunately, these fibers may be used only on ground level floors and not yet for load bearing structures such as ceilings,” he says. “A big step would be the legal use of steel fibers even for ‘freeform’ buildings.”

That is essentially what these BMSF inserts are. While small pieces, they form a mesh-like structure that can be homogeneously inserted into any concrete shape. They can vary in size from 1 to 10 cm, with different wire diameters as well to ensure they fit everywhere in every xyz direction. Together, they can transform tensile forces inside the concrete and make it far more durable. If packed particularly tight, they even form what Kai calls a ‘metal foam’ covered by concrete.

They are also extremely strong. As one test with a filled plate and a compression testing machine (below) showed, they caused the concrete to crack rather than rumble. “Many cracks are a desired sign of high ductility and safety of the building. Each crack is active preventing the collapse of the concrete structure,” Kai says.

The fibers themselves can be delivered as wire coils and are cut, wound and bent into separate shapes. This also makes it highly scalable and adaptable. “The dosage of traditional fibers is limited, since they clump together in the bulk,” Kai says, adding that these BMSF inserts don’t do that. In fact, users have the freedom to create the highest load of steel arming possible (maximizing the steel/concrete ratio). “You can get near indestructible high ductile concrete, the top goal for earthquake-resistant structures,” he adds.

What’s more, the inserts can be integrated into the concrete 3D printing process. While they can of course be manually inserted into any poured concrete, Kai envisions a robotic deposition arm with two nozzles: one for the concrete, and another for depositing the mesh fibers into the concrete layers. While that will require a few more inventions, Kai could be making a huge contribution to construction 3D printing with these BMSF inserts. They are currently patent pending.

Posted in 3D Printing Materials

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