I recently returned from the “3D Concrete Printing Symposium” at TU Eindhoven, and I would like to share an brief overview of the event as well as some thoughts about 3D Concrete Printing (3DCP). The sole idea of this article is to disseminate some general knowledge on 3DCP so as to support the uptake of this technology by the construction industry.

To start with, the symposium hosted about 160 participants — including representatives from the European 3DCP scene — and comprised 17 presentations from academic and industrial members. The complete list of presentation can be found here: TU/e Symposium. While some might have thought that the 17 talks was rather too much for a one-day symposium, the presentations covered complementary topics — ranging from material development and parametric design strategies to automation in construction and structural design aspects on 3DCP; hence, the audience got some good knowledge basis about 3DCP, let alone a clear picture of the challenges involved in the entire 3DCP process.

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TU/e sets the scene with the presentation: “3DCP State of the Art”. (Photo: Courtesy of R. Wolfs, TU/e)

From a 3DCP material outlook, Saint Gobain Weber Beamix shared the steps in the development of a custom 3DCP mortar — starting with their initial studies performed around mid-2000’s (with an interesting video of their early tests, see below) and further developments towards fine tuning the mortar’s rheological parameters, hydration reactions, strength development and volume changes (shrinkage). In principle, their mixture combines CEM I 52.5R, fine sand, and limestone filler — not surprisingly, the mixture also has a number of admixtures that were not specified. Unfortunately, for those who would like to get hands on the product, the so-called custom 3DCP mortar is not yet in the market and the company did not go into details about the potential market price of their custom formulation.

3D Concrete Printing using mortar extrusion.

From a 3DCP reinforcement strategy stance, the presentations from both Bekaert and TU Eindhoven demonstrated an example of how reinforcement can be included in the 3DCP process — sharing some details about how reinforcement cables were added into the fresh mortar printing (or extrusion) process and the mechanical performance of reinforced 3DCP. More details can be found in: “3D printing concrete with reinforcement”. Furthermore, the design aspects of 3DCP are also discussed in the following articles:a) 3D printing of reinforced concrete elements: Technology and design approach and b) Rethinking reinforcement for digital fabrication with concrete.

While the reinforcement solution presented in the symposium is known to some of those following 3DCP, there still exists challenges to overcome — especially when it comes to adding reinforcement perpendicularly to the printing direction. In any case, the Bicycle Bridge project presented by BAM Infra Nederland (in collaboration with several partners, see video below) sets a milestone in the design of 3DCP structures. At present, the main challenge for large-scale applications is that the bridge had to be designed using a “design by testing” approach due to the lack of technical standards. As a result, the total project costs cannot be compared to that of well-established precast concrete element production. Details of the 3DCP printing and assembly processes are available in: “3D-geprinte betonnen fietsbrug

3D Printed Concrete Bicycle Bridge: “Design by testing”.

From a standardization outlook, note that this topic was only slightly discussed during the symposium (in fact, we could make a symposium for that topic alone), it is to my understanding that in a medium-to-long term, where technical standards will encompass the design aspects on 3DCP, the production costs of 3DCP structures is likely to reduce. Consequently, 3DCP will compete against existing construction methods — especially for those concrete elements with unusual shapes. Until then, the construction industry has a crucial role that is to keep investing in independent demonstration projects that showcase the potential of 3DCP, while focusing on the product valorization aspects that can derive from the use of the technology. At the same time, national and international R&D funding programs should stimulate the development of interdisciplinary projects that connect universities, research institutes and industry to enable the further development of 3DCP from a fundamental perspective, e.g. material characterization, numerical modeling of material properties development, elaboration of new reinforcement strategies, to mention a few aspects.

From a technology application standpoint, besides the project results presented by BAM Infra Nederland, CyBe Construction shared their experience with 3DCP and lessons learned from several projects, e.g. the R&Drone laboratory in Dubai, the 3D Housing 05 Villa in Milan. They also shared their upcoming projects — one of which is taking CyBe “back to the desert”, more details on their project will be announced soon. Together with other leading companies in the 3DCP business, CyBe is doing a great job in promoting the potential of 3DCP technology and gradually redefining construction — and their various successful applications is a proof to that.

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3D Housing 05 in Milan. (Source: 3DUp Technical Visit in May, 2018)

From a architectural design perspective, StudioRAP discussed the design process of a modular 3DCP Taxi Stop — this project is being developed in collaboration with Bruil and the City of Rotherdam. Basically, a custom developed form-finding algorithm contributed to determine the optimal shape of the printed construction. The 3DCP structure features a hyperbolic shape, as depicted in the video below, and consists of five concrete modules that are post-tensioned after assemblage. The final results of this project will be featured in late-autumn 2018. Complementary details about the structural design, the form-finding process and general lessons from the project can be found in “Design Process of a 3D-Printed Concrete Water Taxi Stop”.

Form-finding algorithm in action. (Source: StudioRAP)

From a broader perspective, it is clear that the main contribution from events such as this symposium is on the awareness it brings to the engineering community on the fact that 3DCP is a technology that is still in progress. Such awareness is key, since there is a lot of imprecise information about the s3DCP technology and its true potential out there. As stated in the presentation “Potential of 3D Concrete Printing” (by Vertico): “most people think that 3D Concrete Printing will solve everything”, and I could not agree more; especially when I think about the broader audience of people that are not fully informed on 3DCP and the true details of the applications that have been publicized so far. With this thought in mind and in collaboration with the 3DUp project participants and the Danish Technological Institute, we created a rather simple questionnaire to identify how far the public perception is from the actual state-of-the-art of 3DCP technology; so, go ahead and submit your answers to these six 3DCP questions:

Online Questionnaire:What about 3D Concrete Printing?

To complement on your knowledge on 3DCP, I invite the readers to check a recently published paper: 3D printing using concrete extrusion: A roadmap for research. This is an open-access paper written in collaboration with researchers and companies working with 3DCP. The idea was to provide a spectrum of future research exploration in this emerging field and to shed light on the growing number of projects and applications of 3DCP technology over the past few years — some of which are depicted in the chart below.

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Evolution of the number of 3DCP projects and application up to late-2017. (Source: Buswell et al. 2018)

To conclude, I would like to say that the recipe for success in the 3DCP development and market uptake lies in the strong collaboration between universities, research institutes and industry. Such collaboration allows for promoting not only the scientific 3DCP developments but also the uptake of the technology and product valorization. After all, we must work together to deploy 3DCP technology in a robust manner, while providing education to engineers and adding value to construction products rather than simply force 3DCP into standard applications that rely on well-established and efficient construction technologies.

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