
Approximately half of the Block Research Group atop of their 3D sand printed floor structure. Philippe Block (right) is joined on the front row by Dr Tom van Mele, co-director of BRG (centre) and Dr Matthias Rippmann, post-doctoral researcher at BRG who developed the floor prototypes (left).
A tonne of weight rests proudly on a two-centimetre-thick curved shell floor, 3D printed in sand material, achieved only thanks to the formal freedom 3D technology enables.
Accomplished with the ExOne S Print machine, the Block Research Group (BRG) from ETH Zurich STEM University was inspired to rediscover, and reimplement, forgotten techniques that were harnessed hundreds of years ago to construct some of the finest examples of architecture in the world.
The introduction of reinforced concrete in the 19th century saw architects focus more on the material they used, rather than the structure’s geometry, to ensure its strength. Back then it was a development that might have saved a lot of time and effort. Why worry about the complexity of complex geometry, when you can revel in the simplicity of using more material?
As we’ve progressed through to the Digital Age, where technology’s influence in every industry continues to grow, nothing has changed, and structures are all too often produced with a materials-driven strategy. Prof. Dr Philippe Block, who leads the BRG, and contributes to the tonne of weight atop of the 2 m x 1.4 m 3D sand printed floor structure, is a traditionalist, not for the sake of it, but because giving proper consideration to the geometry of the assembly produces some impressive results.

BRG’s 3D sand printed floor with rib-vaulted geometry.
The team designs the complex geometry of the floor's structure on proprietary software that is a speciality of the BRG. Block and his team demonstrate how a weak material like sand can hold close to 1,500kg. He explains if you were to take a chunk of the structure out, you could snap it like a chocolate bar. But as a whole, the rib-vaulted geometry provides sufficient strength per construction guidelines, and with less material used, achieves a 70% weight reduction compared to a typical concrete slab. It’s an old technique, tried and tested, and then forgotten about, or just ignored generation after generation. Thanks to the curious brains of researchers, like Block, and the advancements in tech, like 3D printing, it might finally be remembered.
“To us, it is interesting to use 3D printing, and use these 3D printed models, to demonstrate something that we’ve forgotten how to do – to get strength through geometry rather than through material capacity,” Block tells TCT.
He continues: “We can rapidly generate full-scale prototypes of our new ideas, load test them and demonstrate that you can walk on it, which immediately convinces people. You can put your entire team on it, and it’s even more convincing.”
Of course, it’s only architects who need coaxing. The general public will trust a floor to be safe, wherever it is. In New York’s Grand Central Terminal, the Oyster Bar is sheltered with a vaulted ceiling made of 15cm thick unreinforced tiles. Above them, millions of New Yorkers walk, unaware that a space the size of a small ruler separates them from the atmosphere of a quaint restaurant below.

Block Research Group, ETH Zurich.
BRG’s 3D sand printed floor is made up of five segments.
Block, then, has reason to be optimistic that his group’s 3D sand printing method has potential. The team will showcase the sand printed floor structure on-site as of 2018, and will make the computational framework used to generate the structure’s geometry open source this summer.
Additionally, Block and his team will be using wax 3D printing, a collaboration with Laing O’Rourke’s FreeFAB, to produce the moulds to cast a unit of 5 x 5 m, 2 cm thick, unreinforced concrete floor for the NEST Building in Zurich. Their hope is that it will be a stepping stone in the journey to using an efficient structure in the future. While in this project the material will differ, the geometry remains the key component, and that’s the takeaway from ETH Zurich’s research.
“Many people in 3D printing on a construction scale or architectural scale are suggesting that we are far off from relevant applications because the material is not strong enough,” Block says. “But the material is not strong enough because we haven’t coupled geometries that are in line with what the material is suitable for. If you want to 3D print a structure that stands up because of bending, then these 3D printed materials are going to be useless. However, when you discover a geometry that can activate compression, and that can safely carry all the loads to the supports in compression, then suddenly we have geometries that are highly compatible.”
And when that happens, a stepping stone can become a destination.