New Making Projects

Experiments with concrete and 3D printing

How can I challenge the material properties of an old media? In this case, how can I take an ancient material like concrete – used extensively by the Romans – and test the boundaries of what is conceivably possible? Initial thoughts drove me to where I have seen concrete used before, particularly in building construction and the use of rebar to create reinforced concrete. The way in which steel and concrete support each other and cancel the others weakness shows why it is important for there to be amalgamations of material. Concrete has a relatively low tensile strength, but when joined with steel – which has excellent ductility – the concrete structure then has the tensile strength of steel within.

With this in mind, I considered how it could be possible to take concrete, and create forms which shouldn’t really be made with it. How could I take a particular aspect of one material and combine it with another so they are both supportive and dependant on each other? 3D printing ‘skeletons’ (or frames) is a great way to generate quick, complex and delicate forms. On the other hand, concrete is used in its masses as tough, strong, building blocks to establish towers which loom over cities. When combined we get objects which are fragile yet stiff, convoluted yet solid. The idea seems paradoxical yet interesting.

I made some test pieces which would give an indication of how both concrete and 3D printed skeletons would combine. I printed out a simple sheet of PLA with 5mm² holes in a grid pattern. Having holes makes the form much quicker to print. Dipping the PLA in fine aggregate concrete for different times – 3 seconds, 5 seconds, 10 seconds, 10 seconds with mixing – had changed adhering effects on the plastic, although not much of a difference. In each case, the holes were filled and ‘fleshed’ out, but the smoothest and best result came from mixing. I printed a Meshmixer version of the Stanford bunny which also had a lattice effect, but with holes around 10mm². This time, the gaps were too large for concrete to fill, resulting in only the frame being coated.

The first fully closed form to be made was a simple cylindrical cup shape. As with before, I used Meshmixer to lower the resolution and turn the solid piece to a mesh-like frame before 3D printing. Adhering concrete filled all the holes and gave it a solid, complete skin.

To test the boundaries, I created a helix form in fusion and then used meshmixer to turn the stl into a frame, then printed it. This form was a challenge as it consisted of compound curves and overhangs – neither of which are commonly possible with only concrete. Using gloves, I mixed the concrete by hand, then spread it over the 3D printed frame, resulting in a complex form made from concrete.

I’m not sure what the real life practicalities of this method of making is, but initial findings show the concept works and so can be pushed even further.