2023-10-24 06:30:29
The company XtreeE, a French specialist in large-scale off-site 3D printing, is working with the CNRS and the École des Ponts ParisTech to develop a new type of 3D printed material reinforced with long fibers. More resistant and offering great freedom of form, this new type of concrete, whose industrialization is planned for 2024, will also be more respectful of the environment. Romain Duballet, founder of XtreeE, answered our questions regarding this work.
Romain DUBALLET, Managing Director of XtreeE (credit: XtreeE – Charlène Yves)
XtreeE was created in December 2015, following a research project with the Paris-Malaquais school of architecture.
This pioneer of large-scale 3D printing develops and deploys industrial 3D printing systems for construction around the world.
Romain Duballet is co-founder and Managing Director.
He is also Director of the Specialized Master in Digital Building Design at École des Ponts ParisTech.
Engineering techniques: In a press release[1], you mention an innovation partnership concerning the use of fibers in concrete. What is it regarding ?
Romain Duballet: We are in fact working on the development of a new type of material reinforced by long fibers, in partnership with the CNRS and the École des Ponts ParisTech. The trials are currently being carried out within the Navier Laboratory (CNRS/École des Ponts ParisTech/Gustave Eiffel University). The study is the subject of a thesis[2] co-funded by XtreeE and the CNRS; it is directed by Jean-François Caron, Director of Research at the École des Ponts ParisTech.
More than a material, it is in fact a new process: the coextrusion of a cementitious matrix material and fibers. To obtain concrete reinforced with long fibers, we unwind a reel containing fibers during printing. These fibers can be of various natures, but must respect certain specifications to achieve the desired resistance.
Among the multitude of materials tested (carbon, basalt, glass, steel, etc.), carbon fibers seem to be the most viable and quickest solution to industrialize, because it is the most advanced material in terms of standardization and acknowledgement.
The carbon fiber composite concrete obtained is anisotropic. It has inherent tensile strength and durability, without the need to combine it with other materials like steel. Because you should know that the number 1 problem of concrete durability is linked to the corrosion of steel, itself caused by the carbonation of concrete.[3]. No longer using steel reinforcements therefore avoids any corrosion problems.
XtreeE 3D printing equipment mounted on a robot arm (Credit: ENPC – Charlène Yves)
What can you do with fiber-reinforced concrete printing?
The use of long fibers makes it possible to print parts that we might not obtain until now, to increase the range of possible shapes and therefore to access other markets.
As the mortar is fresh during printing, the difficulty is to be able to print without the structure collapsing before setting. Adding fibers reinforces the resistance in the fresh state and therefore increases the possibilities in terms of shapes.
On the other hand, as fiber drawing increases tensile strength, it also becomes possible to print thin shells that are structural in themselves.
It is therefore a new way of designing concrete which complements our current activities, but which is not intended to replace them.
What are these other activities?
XtreeE offers large-scale 3D printing technology. Although the process itself is multi-material, until now, we have mainly focused our efforts on materials such as concrete and mortars. From high-performance concretes at the start, we have gradually extended the scope of our research to other compositions, in particular low-carbon concretes.
One application of printing technology is so-called permanent formwork, a method of printing a thin concrete skin which will then be filled with another material, for example concrete obtained by traditional casting. You should know that when you need a massive product, it is not at all interesting, in terms of cost and time, to produce it entirely by printing.
This application of permanent formwork has now reached the industrialization stage, since prefabrication factories are already operational in France. This is particularly the case of Spie Batignolles, which is equipped with two XtreeE machines and supplies its sites with printed permanent formwork. The achievements are large-scale: post formwork for the Aubervilliers swimming pool and lintel formwork for the rehabilitation of the Schuman residence in Poitiers, for example.
You mentioned low-carbon concrete. To what extent does XtreeE printing technology reduce CO impact?2 books ?
Firstly, our machines not only allow us to work with materials with a low environmental impact but also to create lightweight structures. A third very important area of impact reduction is the localization of resources. In this sense we are working to develop printable materials from locally sourced raw materials. Furthermore, you should know that the implementation with traditional methods of low-carbon concrete poses many technical problems. Our machines, for their part, allow unprecedented control of pumping, adjuvantation and setting, which makes them tools particularly suited to working with these innovative materials.
As far as fibering is concerned, reinforcing concrete with carbon fibers avoids steel corrosion problems and therefore ultimately allows the quantities of clinker in mortars to be considerably reduced.
We are therefore gradually moving towards obtaining a low-carbon fiber material, even if our efforts are for the moment mainly focused on the robustness of the process, because the industrialization of the “long fiber” solution is planned for 2024. !
[1] Available at this address
[2] In continuation of the work carried out within the framework of two other theses concerning fiber reinforcement
[3] Natural CO capture2 with time
Image credit of one: ENPC – Charlène Yves
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