ABSTRACT
This paper discusses the design, fabrication, and assembly of the 'Eggshell Pavilion', a reinforced concrete structure fabricated using 3D printed thin shell formwork. Formworks for columns and slabs were printed from recycled plastic using a pellet extruder mounted to a robotic arm. The formworks were cast and demoulded, and the finished elements were assembled into a pavilion, showcasing the architectural potential of 3D printed formwork. The Eggshell Pavilion was designed and fabricated within the scope of a design studio at ETH Zurich. The structure was designed using a fully parametric design workflow that allowed for incorporating changes into the design until the fabrication. The pavilion consists of four columns and floor slabs. Each column and floor slab is reinforced with conventional reinforcing bars. Two different methods are used for casting the columns and floor slabs. The columns are cast using 'Digital casting systems', a method for the digitally controlled casting of fast-hardening concrete. Digital casting reduces the hydrostatic pressure exerted on the formwork to a minimum, thereby enabling the casting of tall structures with thin formwork. The floor slabs are cast with a commercially available concrete mix, as the pressure exerted on the formwork walls is lower than for the columns. In this research, 3D printed formwork is combined with traditional reinforcing, casting, and assembly methods, bringing the technology closer to an industrial application. Supplementary Information: The online version contains supplementary material available at 10.1007/s41693-023-00090-x.
ABSTRACT
Concrete construction harms our environment, making it urgent to develop new methods for building with less materials. Structurally efficient shapes are, however, often expensive to produce, because they require non-standard formworks, thus, standard structures, which use more material than is often needed, remain cheaper. Digital fabrication has the potential to change this paradigm. One method is Digital Casting Systems (DCS), where the hydration of self-compacting concrete is controlled on the fly during production, shortening the required setting time and reducing hydrostatic pressure on the formwork to a minimum. This enables a productivity increase for standard concrete production. More importantly, though, it enables a rethinking of formworks, as the process requires only cheap thin formworks, thus, unlocking the possibility to produce optimised structural members with less bulk material and lower environmental cost. While DCS has already proven effective in building structural members, this process faces the challenge of moving into industry. This paper covers the next steps in doing so. First, we present the benchmark and expectations set by the industry. Second, we consider how we comply with these requirements and convert our fast-setting self-compacting mortar mix into a coarser one. Third, we present the next generation of our digital processing system, which moves closer to the industrial requirements in terms of size and the control system. Finally, two prototypes demonstrate how DSC: (a) increases standard bulk production by 50% and (b) can be cast into ultra-thin formworks. We discuss the results and the short-term industrial concerns for efficiency and robustness, which must be addressed for such a system to be fully implemented in industry.
