Additive Construction (2022-04)¶

Globally, we continue to be in a phase of strong urbanization. The numbers are striking: in the next 50 years, we will build more buildings than we did in the last 2000 years, which is the equivalent of adding an entire New York City to the world every month. Hence, we need to urgently develop strategies to build more affordable and more sustainably. One of the main challenges in construction is that buildings are usually one-of-kind solutions—adapted to their unique context. For optimized structures, large-scale complex geometries are required that are usually difficult and expensive to fabricate. Digital fabrication and especially robotic additive manufacturing are beginning to play a central role in improving productivity for these cases. Today, additive construction entails a wide variety of processes, including robotically stacking bricks, automated assembly of timber elements, actuated formwork systems, and much more. The scale can range from three-dimensional (3D)-printed connections, to facade panels, to large-scale structural elements in which the target object is bigger than the 3D printer itself. Recent developments in construction robotics allow us to scale up additive manufacturing and work not only in controlled prefab environments but also in onsite conditions. After the first issue with a focus on concrete extrusion, this second special issue concentrates on the complementary strategy: additive manufacturing of formwork. Formwork plays a major role in conventional cast concrete construction. The more complex the targeted concrete shapes are, the more labor and resource-intense is the fabrication of the formwork. A second temporary architecture for the negative mold is required. Consequently, the engineer Pier Luigi Nervi already described in 1956 the limitations of concrete construction as the ‘‘unconquerable inertia of our minds’’ and the ‘‘trivial technicality of the need to prepare wooden frames.’’ The submissions presented in this issue demonstrate the potential of additive manufacturing to overcome these limitations. 3D printing the negative molds for concrete has unique advantages compared with directly 3D printing concrete: It is possible to use well-established concrete material systems and conventional reinforcement solutions. Cast concrete usually develops superior surface qualities and material properties compared with 3D-printed concrete. Similar to the application of 3D-printed molds in other domains, one could argue that 3D printing concrete formwork combines the best of both worlds: the superior quality of cast concrete with the geometric freedom of additive manufacturing. Although the first buildings have already been constructed using 3D-printed formwork, major open research questions remain. Formwork has to withstand the concrete pressure, has to be easily removable, and should result in a high-quality concrete surface. As always in the domain of construction, the speed and cost of fabrication of 3D-printed formwork systems are crucial factors. But also the life cycle of the used materials, their recyclability, or reusability are becoming more and more relevant. This issue starts with a detailed overview of various approaches to 3D-printed formwork. It then discusses a novel robotically winding strategy for large-scale custom formwork. Fused filament fabrication is a common strategy for formwork printing. The next article investigates the chemical interactions between concrete and thermoplastic formwork to enable efficient counter-pressure casting of concrete. The final contribution does not specifically address formwork but delivers essential insights into temperature management of large-scale fused filament fabrication. I would like to thank all the authors and reviewers for their greatwork thatmade these valuable contributionspossible. This issue could not have been done without the fantastic editorial team around Skylar Tibbits and especially Anastasia Hiller. As always, your comments are welcome. For feedback and direct contributions to the journal, contact us at (3dpeo@ liebertpub.com). We are witnessing another turning point of construction, and it is our chance to determine its new direction. We need to learn to harness the full potential of additive manufacturing—toward a digital building culture and a more diverse and sustainable built environment.