Digital concrete fabrication

The object features the terrains of the areas of each campus in the corresponding colors of the concrete used for each of them.

The 3D terrain data has been sourced from the geodata of the swiss topography office website. Those data consist of a height map converted into a 3D mesh using QGIS with the DEMto3D plugin. The final object has been modeled in Blender.

A detailed guide on how to generate the terrain model is available here.

Being a new project for the Fablab SUPSI, we started prototyping with different processes.

From the 3D printed brick model, the vacuum forming was the first attempt to create a negative shape to pour the concrete into. The sharp edges and the vertical sides of the object weren't ideal for that technology. We did some testing, but this option got scrapped quite quickly.

The solution adopted was to create a silicon mold. The great advantage of silicone is that it captures every detail of the object, is elastic and flexible, facilitates the removal of the concrete once dry, and can be reused many times.

We built a fromwork with the laser cutter and a structural box for the pouring to create the silicon mold.

The goal was to build the object with two different concrete colors, representing the color of the respective campuses (one is gray, the other reddish).

For the gray one, there was no problem; it was just regular portland concrete. We added some iron oxide powder to the sand and cement mix for the red side.

We simplified the mix from the initial test that included some glass fibers and round stones (max 8-10mm in size) because, being a small display object, those elements tended to ruin the overall look and polish.

The final recipe was simple, 2kg of fine sand, 1.7kg of cement, and 0.8L of water. We added 35 grams of iron oxide to the red concrete.

The setup and production of 25 bricks have been carried out in about two weeks. We produced five bricks daily thanks to the five silicone molds we created.

The more significant part consisted of learning and creating a process to efficiently and successfully produce the bricks. Here are the steps we went through:

1) Designing the object in 3D, prototyping the process, and testing the concrete mix

2) Designing and building the formwork to create the silicon molds

3) Pouring the concrete into the molds and let them dry

4) Sending the bricks and covering them with a protective layer (paraloid B72 at 2.5% in acetone)

5) Gluing the laser-cut text plates

6) Documenting the whole process with a video