CONCR3DE co-founder Eric Geboers talks 3D printing stone, Notre-Dame and scaling

A couple of weeks ago, a Dutch 3D printing startup named Concr3de came onto our radar when it demonstrated how its unique stone additive manufacturing technology could reproduce a damaged piece of Notre-Dame de Paris using materials sourced from the cathedral’s burnt and damaged structure.

Like many other media outlets, this caught our attention for a number of reasons. For one, with all the discussions surrounding the destructive Notre-Dame cathedral fire and future restoration efforts, the prospect of a 3D printed solution was undeniably exciting. For another, while we’ve seen sand and concrete 3D printing for architectural applications, the ability to precisely 3D print stone materials is less usual. All that to say, we wanted to know more,

We recently caught up with Concr3de co-founder Eric Geboers who gave us a look into Concr3de’s unique 3D printing technology and its aspirations in the 3D printing and architecture sectors.

Concr3de’s origin story

Concr3de was founded in 2016 by Geboers and Matteo Baldassari, two Delft/Rotterdam-based architects who set out with the common goal of creating a way to produce unique and affordable designs for the architecture and construction industries, among others.

“I studied in Delft and Matteo in Rome, Italy,” Geboers explains. “We both had our own companies: I was designing and producing furniture pieces on a small production scale and Matteo worked as a tutor in Delft as well as an architect for a few design companies. He also had a company of his own, working with robotic architecture. We got together and were basically looking for a way to make a technology that could affordably transform digital geometries into durable physical geometries.”

“We wanted to work with inkjet printing, which we like because it gives you a lot more freedom than standard FDM,” he adds. “You can print more complex shapes and it gives a nicer finish. With that in mind, we started off by buying an old ZCorp 3D printer which we hacked until it was almost destroyed. We also realized that we wanted to print stone materials that could be customized and that would be durable and affordable, and we realized we had to develop the 3D printer from scratch, as well as software, inks and powder materials.”

Like a printing stone

The resulting technology developed by Concr3de is a unique inkjet platform that utilizes industrial stone byproducts and a chemical binder to build up durable stone structures. Presently, the company has two 3D printing platforms: the Armadillo White and Armadillo Black. The former is an open system that is ideal for research applications and developing new materials, while the latter can be integrated into studios or offices for prototyping or production.

“What exists in the market now for binder jetting is basically sand printing for metal casting—like what voxeljet and ExOne do—and gypsum or plastic printing—like what HP and 3D Systems offer. These all work with a kind of glue that binds particles together and is then sintered or removed,” says Geboers. “Instead of gypsum and glue, we use industrial waste materials, such as powders from marble or granite quarries, which we mix with a special cement-like material.

“We then print a chemical top of a layer of this powder material, which binds the particles together through a chemical reaction. It’s inorganic chemistry: there are no plastics or resins involved in the process. The final product is really stone.”

“The cool thing is is that after printing, we dip the part in water and then it’s done,” he continues. “We don’t need sintering, which makes the process quite cheap. It usually takes 1 day to harden, 28 days to fully cure until the printed part is completely inert—there are no hazardous materials in it.”

Industrial byproducts

Though using industrial byproducts as a material base is affordable, it also comes with certain challenges. As Geboers explains, it is essential that the powders supplied by the quarries have the right chemistry and dimensions for optimal printing.

“We need the right size and shape of grain,” he says. “We can’t just take in any kind of dust or powder, it needs to be very specific in terms of dimensions. When we receive the powders, we mix them with our cement-like material in the right proportions for printing.”

Perhaps one of the most interesting things about Concr3de’s 3D printing technology is its ability to print a broad range of materials, including customized stone powders. Currently, the company has three materials on offer—grey granite, white Carrara and foundry sand—though it is always experimenting with new combinations. For the Notre-Dame project, for instance, the gargoyle was 3D printed using a mixture of limestone and ash.

Geboers  explains: “We’ve gotten pretty good at tweaking the materials, because we experiment so much. Right now, we are working with granite, Carrara marble, basalt and other natural stone materials. We can also customize certain colours or finishes for clients.”

Stone printing applications

In terms of applications, Concr3de is mainly working in the research area right now as well as working closely with clients to explore its stone 3D printing technology.

“Most of the things we do are collaborations,” says Geboers. “Our technology does require specific knowledge, especially for developing your own materials. Right now, we’re working on research applications with universities. We also do a lot of prototyping with architects and designers. For example, we recently had a project at the Salone del Mobile design fair in Italy last month.”

There is also the potential for construction applications. As the Concr3de co-founder elaborates: “Our technology could be used for printing finishing touches for buildings, like a wall panel or piece of furniture. But you could also print a hollow piece and cast a material inside of it to use a structural element, like a column.”

Notre-Dame and restoration

As evidenced by the proposal to help rebuild the Notre-Dame cathedral, restoration and cultural preservation are high up on the list of Concr3de’s applications. Prior to the Notre-Dame project, the company’s unique AM technology was also used to 3D print a piece of a reproduction Palmyra Arch—whose original was famously destroyed by ISIS in Syria.

“What you see now is that a lot of restoration isn’t happening, either because it is too expensive or the skills are lacking,” Geboers says. “People are not doing the sort of craftsmanship that they used to. In Holland, for example, there are maybe three stone masons left. So that’s something that is really interesting to us because there is potential to restore things with new technologies.

“It also comes with challenges, such as the ethical question of what is allowed; can you restore historical artifacts with new technologies? But 3D printing is much cheaper and faster for restoration applications, and there is a lot that can be done with it.”

A stepping stone to large-format

In addition to continually experimenting with new stone materials, the Concr3de team is also working on enlarging its 3D printing technology to open up new applications.

Geboers explains: “Right now, the technology works at a relatively small scale—a prototyping scale. When you scale it up to a larger volume, however, it gets really interesting. We are working on that now and because the materials we take in are cheap and we work at room temperature (there are no complex heating or cooling elements involved) it’s very possible. Within a year, we hope to have a larger 3D printer with a build volume of up to 2 cubic meters. This will open up lots of unique opportunities in architecture, art and design.

“We’re looking to work with people who are interested in large scale printing and who want to get involved in this stage of development. It is important for the customer to give input into the design of the machine.”