Jul 31, 2018 | By Thomas

Researchers at ETH Zurich have realized an 80 m² lightweight concrete slab at the DFAB House, making it the world’s first full-scale architectural project to use 3D sand printing for its formwork.

Last year a team from ETH Zurich university in Switzerland started a three-storey house project called DFAB House. Unlike construction projects that use only a single digital building technology, such as 3D printed houses, the DFAB House will be the first house in the world to be designed, planned and built using predominantly digital processes.

Construction of the DFAB HOUSE is moving forward rapidly. Now the team has completed what is known as the Smart Slab, a lightweight concrete slab spanning 80m2 at the DFAB House. Just 20 mm thick at its thinnest point, the slab combines the structural strength of concrete with the design freedom of 3D printing. For the Smart Slab project, the researchers did not produce the building components themselves with 3D printing but rather the formwork – i.e. the mold.

The structural principle of the Smart Slab is a hierarchical grid of post-tensioned ribs cantilevering from the Mesh Mould Wall. (Photograph: ETH Zurich / Andrei Jipa)

The 80 m2, 15 tonne ceiling consists of eleven concrete segments and connects the lower floor with the two-storey timber volume above. One of the advantages of using 3D printing for the mold instead of using layered concrete process is that high performant fibre-reinforced concrete can be used and the structure can be fabricated in the precision of millimetres.

The Smart Slab was developed by the research group of Benjamin Dillenburger, Assistant Professor for Digital Building Technologies at ETH Zurich. The research group developed a new software to fabricate the formwork elements, which is able to record and coordinate all parameters relevant to production. In addition to basic data such as room dimensions, the researchers also entered a scan of the curved wall which acts as the main support for the concrete ceiling. The software allows them to adapt the geometry of the slab so that at each point it was applied only as thick as structurally necessary to support the force flow.

“We didn’t draw the slab; we programmed it,” says Mania Aghaei Meibodi, Smart Slab project lead and senior researcher in Dillenburger’s group. “It would not have been possible to coordinate all these aspects with analogue planning, particularly with such precision.”

The ceiling features an organic ornamental structure with different hierarchies. The main ribs carry the loads, while the smaller filigree ribs are mainly used for aesthetic appeal and acoustics. The lighting and sprinkler systems are also integrated into the slab structure. Their size and position were similarly coordinated with the planning software.

Complex geometric features articulating the concrete surface of the Smart Slab. (Photograph: ETH Zurich / Demetris Shammas)

Several industry partners were involved in creating the Smart Slab. One produced the high-resolution, 3D-printed sand formworks, which were divided into pallet-sized sections for easier printing and transport. Another partner fabricated the timber formwork by means of CNC laser cutting, which gives shape to the upper part of the Smart Slab and leaves hollow areas that reduce material and weight and create space for electrical cables. The third company brought together the two types of formwork, spraying the fibre-reinforced concrete onto the sand formwork to produce a ribbed surface of the lower concrete shell and casting the remaining concrete into the timber formwork.

The 3D sand printer used for the fabrication of the formwork. The printer has a build volume of 8 cubic meters and a resolution of a fraction of a millimeter. (Photograph: ETH Zurich / Tom Mundy)

Post-processing of the 3D printed formwork parts. Unconsolidated sand particles are being removed from the print bed. (Photograph: ETH Zurich / Tom Mundy)

An oil-based release agent facilitates the removal of the formwork once the concrete hardens. (Photograph: ETH Zurich / Andrei Jipa)

Glass-fibre reinforced concrete being sprayed on the 3D printed formwork in several consecutive layers. (Photograph: ETH Zurich / Andrei Jipa)

The formwork parts are assembled seamlessly and prepared for concreting. (Photograph: ETH Zurich / Andrei Jipa)

It took two weeks to harden the concrete. The 11 individual concrete segments were transported to the DFAB House. A crane placed the concrete elements onto the load-bearing wall, where the prestressing took place. Workers pulled steel cables lengthwise and crosswise through the concrete support and into the channels already inserted in the formwork. Tensioning the cables massively increases the system’s load capacity.

The final and largest segment of the Smart Slab - weigthing almost 2.5 tonnes - being installed on site. (Photograph: ETH Zurich / Andrei Jipa)

“It was spectacular to see on the construction site how seamlessly our elements fitted with each other and with the existing components of the DFAB House,” says Dillenburger. “We owe this in part to the outstanding interdisciplinary collaboration with our partners. The meticulous work that we had invested into planning completely paid off.”



Posted in 3D Printing Application



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aa wrote at 8/2/2018 10:49:19 AM:

No. It is still too primitive. We have to change fundamental paradigm. ETH or C.A.S.T are quite close but not enough.

aa wrote at 8/2/2018 3:54:23 AM:

no. it is quite nice but still too primitive. but i know how to do this. look. how many news give to us this nice website? (i thank you for that) and what? what really change? almost noting because we are still in the wrong paradigms it is new, better way. please, remember my words - for exemple cities will have higher biomass than national parks... when you need to buy table and chair you will go shopping with no car, two bigger pockets that fit volume of two cola can is enough

Ben432 wrote at 7/31/2018 2:16:49 PM:

It looks like we are ready to print habitats on Mars.

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