3D Printing with Waste from Marble Quarries

Researchers from ETH Zurich and SUPSI's Institute of Earth Sciences have developed a 3D printer that uses a waste byproduct material derived from stone processing. Researchers Francesco Ranaudo from the Block Research Group and Pietro Odaglia from the chair of Digital Building Technologies provide insight into the innovation and the connection between a Ticino stone quarry and the Venice Biennale.

What does stone granulate have to do with digital fabrication?

Digital fabrication and additive manufacturing technologies are continuously evolving and broadening the range of usable materials. Our project introduces stone aggregates with granulometry in the 0-4 mm range, as a viable material for the 3D printing of large-scale, structurally sound components for construction applications. Around 80% of the printed volume is made up of recycled aggregates, mitigating waste disposal issues and the demand for new materials.

Why is the disposal of construction and quarry waste a problem?

Each year, the extraction, processing, and transport of billions of metric tons of construction material take place globally. A significant proportion of waste from construction (up to 40% ) goes directly into landfill. This research has developed a potential to convert part of this waste material into high-value construction products. Our partners at the Cava di Arzo quarry in Ticino are deeply ingrained in the socio-economic fabric of the region, and are strongly interested in developing new markets and improving their business impact. This partnership and these technologies provide constructive solutions for sustainably managing their waste.

Researchers Pietro and Francesco on the printed slab on site in the Ticino quarry in front of the mobile 3D printer.

You both are researchers in the NCCR DFAB with different areas of expertise, your research is interdisciplinary. What are you contributing to the project?

Francesco: The 3D printed elements from this new process achieve very good mechanical properties in compression, but are limited in tension. Moreover, the printer is limited in the size of the elements than can be produced. My research investigates optimised structures, that make use of weaker and yet more sustainable materials like recycled marble granulate. For this project, I designed a structural floor discretised in 17 parts that can all be produced within our 3D printer's dimensions. Thanks to the funicular (compression-only) geometry of our structural designs the blocks can be assembled without the use of any mortar, reinforcing or complex connections.

Pietro: With my experience in computer aided manufacturing and through access to the labs and facilities of ETH, I was able to design our technology from the ground up. I developed the 3D printing process, including hardware, software, and material integration. Through collaborations and support from several specialist colleagues within the NCCR we were able to tackle many of the most considerable challenges. Our "slicer" software helps manage the most relevant printing parameters, including how to prepare jobs for our complex hardware configurations (i.e.: how to instruct 8 nozzles which are all moving on a rotating axis). What we present today is the result of 4 years of research, 3 prototypes, and countless iterations of material testing.

The printer was manufactured in-house but is now able to be used on-site in a mobile container. What is the difference between in-lab or on-site printing?

Many fabrication processes require specific environmental parameters, such as temperature and humidity, creating challenges to operate outdoors or on-site. While developing our process, we have aimed to minimise these restrictions. The outcome is a versatile and transportable printing unit that can function either inside with the comforts of a controlled environment or be shipped to a construction site for in-situ operations.

The 3D printing process, including hardware, software and material integration, was designed and developed by Pietro Odaglia.

What is the biggest challenge in 3D printing with this material?

Our method is based on Binder Jetting (BJT), 3D printing that uses a binding compound to selectively bond the material layer after layer to create specific solid geometries. Due to the coarse material as aggregate we went through many development iterations for the material system, actuators, printheads, and the recoaters. The main printing parameters such as resolution, production rate, linear speed, and binder flow rate are all affected by the broad granulometric profile of the material mix.

Pietro, this innovation is based on a common 3D printing. How is this process different from more conventional applications of BJT?

The binder being used was developed as part of Vera Voney's Ph.D. research at the Chair of Sustainable Construction. It is a two component binder using a granular base and an activating liquid alkali solution. The solution is dispensed through nozzles, layer by layer to bind the conglomerate via geopolymerisation. The result is a durable 3D printed part, with excellent mechanical capacity and resistance to weather and fire.

Is this a sustainable 3DP process because it uses waste material? or is this title not possible due to the binder, for example?

Sustainability is a widely discussed and challenging topic to quantify. This question was at the forefront of our efforts and development decisions. In this work we designed a printing process that can use virtually any particle material and bind it with an inorganic compound. This allows most of the volume of our manufactured components (currently 80%) to be sourced from any industry that produces granular waste or byproducts ( such as stone extraction). While both components of the binder have relatively low environmental impact, we are actively researching ways to further minimise this, but already our innovations create new opportunities for increased circular material economy with granular materials.

The Slab is on show at Palazo Mora during the Architecture Biennale.

This year you are presenting a funicular floor printed with this new material system at the Venice Architecture Biennale . What does this contribution mean to you?

Ribbed, funicular structures have been present throughout the history of Architecture and Engineering. In 2016 the Block Research Group exhibited our first ribbed funicular floor slab using 3D printing in the Venice Biennale. This year we update the concept and showcase how we can further refine such structures and optimise sustainability by exploiting widely available, low-performance waste materials to produce such novel construction components.

You recently completed the prototype. What is the next step?

The fabrication of this prototype gave us new insight on several aspects of the process. We will continue to further develop and improve the production processes and technologies. Our latest mechanical tests show compression strengths above 30 MPa after only 7 days, significantly shorter than concrete (28 days): and with this knowledge we feel that we can work to dramatically increase the speed of production. Additionally we plan to undertake mechanical load testing of the 3D printed slab currently exhibited in Venice - and compare it with the previous prototype slabs tested by BRG. Such testing of similar components enables comparison to many previous iterations, and we are able to contextualise our structural developments. Finally, we are in discussion with several companies to develop industry capability for industrial production. Our ultimate goal is to effectively transfer and deploy this innovation for construction applications in the future.

The mobile 3D printer is used in the Cava di Arzo quarry in Ticino, Switzerland.

Pictures by Pietro Odaglia

This research is supported by Innosuisse.