It seemed wildly unbelievable at first: 3D printing large-scale structures strong and stable enough to serve as offices, villas or even entire apartment buildings. However, since the concept of additive construction first started to translate from idea into physical reality, numerous examples have materialized to demonstrate that 3D printing buildings is not only feasible, but it may even be better than traditional techniques in some regards.
As this emerging technology begins to evolve, new players and processes are taking shape, such as the large binder jetting–style system of D-Shape and the numerous gantry-style printers from small startups and DIY engineers. In France, a startup called XtreeE has developed its own technology for additive construction. Working with partners Dassault Systèmes, LafargeHolcim and ABB Robotics, the firm demonstrated just how capable that technology is by 3D printing a 4-m-tall (13.1 ft), concrete pavilion.
While Dassault Systèmes developed a 360-degree video with a great overview of the XtreeE Pavilion’s construction, Philippe Morel, president of XtreeE, provided ENGINEERING.com with his own insight on the project, as well as the impact of 3D printing on the architecture, engineering and construction (AEC) industry overall.
The Founding of XtreeE
Outside of XtreeE, Morel is the cofounder EZCT Architecture & Design Research, as well as an architect and theorist. Throughout his work, there is an emphasis on computational architecture, a field in which Morel is a thought leader. The Digital Knowledge department at the ENSA Paris-Malaquais, which he cofounded and where he directs the graduate program, explores the use of digital design and fabrication tools.
“I always worked at the intersection of architecture, engineering and technology, both on a practical level (being implied in the development of construction methods) and a theoretical level (through the publication of numerous essays in specialized magazines and academic publications),” Morel said.
XtreeE’s first 3D-printed prototype. (Image courtesy of XtreeE.)
“After being involved in many projects related to the use of 3D printing,” Morel explained, “I felt the necessity to develop new approaches that could overcome the limitations of what I saw within the existing technologies. Therefore, when I saw that we could apply for a grant thanks to the DEMOCRITE project, with a researcher named Justin Dirrenberger, I knew that we could move a step further towards large-scale 3D printing.”
Through the DEMOCRITE project, Morel and his team were able to demonstrate the ability to construct large, complex structures. The first prototype was a 2-m x 1.5-m (6.7-ft x 4.9-ft) wall with an internal structure derived from a double sine curve and capable of being filled in with such construction materials as thermal insulation.
“At the end of this highly successful academic project, we chose to work with my former students, colleagues (material scientists, computer scientists, etc.) and individual investors already active in the construction materials industry to pursue the project within some sort of a spinoff company,” Morel said. “And XtreeE was born.”
Additive Construction
XtreeE is not the first firm to embark on additive construction. Among the other players in the market working on this exciting technology are D-Shape, one of the first to attempt large-scale 3D printing for building purposes, and WinSun Global, a Chinese firm that has achieved many firsts, including the construction of the first 3D-printed apartment complex, villa and office building.
XtreeE, however, sets itself apart from these companies. “[Our process] is fundamentally different from D-Shape, as this company uses a powder bed paradigm,” Morel pointed out. “D-Shape machines hydrate a cementitious powder and use the non-hydrated powder as supports. Then when the final piece is consolidated, one has to remove the unnecessary and unused powder. This technique is great regarding the geometric freedom offered by the natural supports via the powder bed, but personally I believe it is too slow, unreliable (due to the difficulty of hydrating cementitious powder in a satisfactory and regular manner) and very unpractical (due to the fact that one has to remove the powder, clean the piece, etc.). When one is dealing with small pieces, this is fine, but when one is dealing with pieces that weigh multiple tons, it becomes a very important and tricky issue.”
He added, “Regarding WinSun, the paradigm is the same, but we believe that we can produce more accurate pieces made of ultra-high-performance concrete and with greater geometrical complexity.”
XtreeE’s 3D printing process is similar to the fused deposition modeling technology seen in many desktop 3D printing systems in that a material is extruded from a printhead. Swap out the boxy gantry for an industrial robotic arm and the thermoplastic for a viscous building material like concrete and you’ve got the foundation for additive construction.
In the case of XtreeE, the robotic arm manufacturer of choice is ABB Robotics. For the pavilion project, XtreeE outfitted the IRB 8700, ABB’s largest robotic arm, with a specialty concrete extrusion system. The concrete used by XtreeE was developed by yet another partner, LafargeHolcim, one of the largest manufacturers of building materials in the world. For XtreeE’s process to work, the cement must be both light enough and able to dry quickly enough to harden and support subsequent layers.
Therefore, XtreeE has used an experimental cement developed by LafargeHolcim R&D based on the company’s ultra-high-performance concrete, Ductal. LafargeHolcim claims that its Ductal material is 6 to 8 times stronger and lasts 2 to 3 times longer than standard concrete due to the fact that it is reinforced with metal fibers, which also allows it to survive environmental conditions.
With this technology, XtreeE was first able to 3D print a large, load-bearing structure, the 4-m-high Krypton Post, used to support the playground roof of a French middle school. Quickly increasing the scale of its structures, XtreeE then set about printing a complete pavilion.
The 3D-Printed XtreeE Pavilion
To demonstrate the ability of XtreeE’s technology to form entire buildings, the firm first created the XtreeE Pavilion. According to Morel, the design for the pavilion came from nature.
“The inspiration came both from very elementary and highly “mineral” shelters (as in many Mediterranean countries) and from natural forms,” Morel said. “Thanks to the power of computational tools, we were capable of merging these inspirations into a pavilion that makes use of advanced 3DS topological optimization tools while remaining very simple and elegant—very ‘basic.’ I strongly believe that the power of technology should be oriented towards the search of a new kind of simplicity.”
As a part of Dassault Systèmes’ startup accelerator 3DEXPERIENCELab, XtreeE uses the company’s software throughout the entire design and construction process. “It was used at each step,” Morel said, “from the very first sketches on tablet PCs to the FEM structural analyses. Having the opportunity to deal with every aspect of a project on a single platform is amazing. It makes the workflow much smoother and much more efficient.”
Due to the experimental nature of LafargeHolcim’s material, structural analysis was an important element to understanding how the concrete would behave. Such features as generative design exploration and topological optimization allowed the XtreeE team to then determine the ultimate form of the pavilion.
Unlike WinSun’s approach, which sees walls and other elements 3D printed offsite and assembled on location, XtreeE was able to 3D print the entire structure—including walls, roof and built-in seating—in one continuous process.
Building an Additive Construction Industry
Ultimately, additive construction promises some new benefits to the AEC industry. By using only the material that will actually go into the final construction of a building, 3D printing may make it possible to eliminate material waste entirely, while also limiting the need to transport supplementary and unused materials to the construction site.
Moreover, the ability to print complex geometries opens up new design ideas that aren’t possible with traditional techniques. These designs can also be optimized to cut down on energy consumption, relying on passive heating and cooling rather than electrical systems.
Another benefit, according to Morel, is the ability to produce structures on-demand and with mass customization in mind. The design flexibility allows for, not just replicating existing structures, but the creation of entirely new types of buildings.
New design techniques, however, may not be easy to incorporate into an established industry, Morel said. And while additive construction firms may have to deal with the same kind of safety and compliance issues faced by traditional companies, there is not yet a standard for 3D printing in the construction industry.
Morel explained that obstacles facing the world of additive construction include “setting new standards and showing people how beneficial large-scale 3D printing can be. For this, one has to deal with new design practices. If we just try to replicate what already exists, but through 3D printing, we will miss an amazing amount of opportunities.”
To prove just how beneficial this technology will be, XtreeE aims to 3D print a functional structure. Though he did not elaborate on what this would look like, Morel did say that he hopes that it will take shape “very, very soon,” within the next 18 to 24 months.
To get an immersive feel for what goes into 3D printing a concrete pavilion, grab your virtual reality viewer and watch the 360-degree video below.