According to Digital Building Technologies, researchers at the Swiss Federal Institute of Technology Zurich (ETH) and the University of Applied Sciences and Arts of Southern Switzerland (SUPSI) have developed a 3D printer designed to transform large quantities of stone waste from quarries into customizable architectural elements. The stone waste, or rock flour, in places like Ticino, can constitute up to 40% of total production. The printer was demonstrated in a case study, where it fabricated an optimized floor system using the byproduct of a marble quarry in Ticino.
Source: Digital Building Technologies.
This project offers a real-world example of how 3D printing can reduce overall construction material consumption and foster the usage of local, recycled resources. The final product, an assembly of the floor system, will be showcased at the Venice Architectural Biennale in 2023.
The team at ETH Zurich has innovated upon the existing Binder Jetting (BJT) 3D printing method. The traditional BJT, which uses a binding compound to solidify granular material layer by layer, was found to have limitations for construction use due to the brittleness of printed parts and poor fire and weather resistance. The researchers propose an alternative binder based on geopolymer – leading to a redesign of both the hardware and software known as Geopolymer Binder Jetting (GeoBJT). This system not only improves the performance of the printed parts but also allows a wider range of materials for binders and particles, and higher build-up rates. Furthermore, it employs a mobile container-based setup for on-site operation, akin to a field factory.
Manufacturing on Demand
Source: Digital Building Technologies.
Mechanical tests on the redesigned system have shown a substantial increase in the mechanical response of the printed parts, with the strength of the parts now comparable to concrete – achieving averages above 30MPa in compression and 5MPa in tension.
The chosen geopolymer binder has several advantages. It is an amorphous material synthesized by mixing an aluminosilicate source with an alkaline activator, offering strength similar to concrete but with a lower CO2 footprint. This binder is used in a jetting technique, replacing metakaolin with blast furnace slag, and integrating underused by-products like rock dust from marble quarries. Moreover, the binder has excellent moisture buffering capacity, potentially increasing building resilience during extreme heat waves.
Source: Digital Building Technologies.
For the Ticino case study, the researchers fabricated a rib-stiffened funicular floor using discrete, prefabricated components. The design was based on a previous case study and adapted to address material, fabrication, and installation constraints. The prototype consists of 17 discrete elements assembled with dry joints, forming a rectangular vaulted structure supported at its corners. The study demonstrated the potential of additive manufacturing processes in creating structurally optimized and economically feasible building components, particularly suitable for compression-dominant systems.
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Author: Edward Wakefield
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