Eggshell: Ultra-Thin Three-Dimensional Printed
Formwork for Concrete Structures

Joris Burger,1,* Ena Lloret-Fritschi,1,2,* Fabio Scotto,1,2 Thibault Demoulin,2 Lukas Gebhard,3
Jaime Mata-Falco´ n,3 Fabio Gramazio,1 Matthias Kohler,1 and Robert J. Flatt2
1Department of Architecture, Chair of Architecture and Digital Fabrication, ETH Zurich
2Department of Civil, Environmental and Geomatic Engineering, Physical Chemistry of Building Materials, Institute for Building
Materials, ETH Zurich
3Department of Civil, Environmental and Geomatic Engineering, Institute of Structural Engineering, Concrete Structures and Bridge
Design, ETH Zurich

Concrete is a material favored by architects and builders alike due to its high structural strength and its ability to take almost any form. However, to shape concrete structures, heavy-duty formwork is usually necessary to support the fresh concrete while curing. To expand geometrical freedom, three-dimensional (3D) printed concrete formwork has emerged as a field of research.

This article by Joris Burger, Ena Lloret-Fritschi, Fabio Scotto, Thibault Demoulin, Lukas Gebhard,
Jaime Mata-Falcon, Fabio Gramazio, Matthias Kohler, and Robert J. Flatt, presents one possible application, a novel fabrication process that combines large-scale robotic fused deposition modeling 3D printing with simultaneous casting of a fast-hardening, set-on-demand concrete.

This fabrication process, known as ‘‘Eggshell,’’ enables the production of nonstandard concrete structures in a material-efficient process. By casting a fast-hardening concrete in a continuous process, lateral pressure exerted by the fresh concrete is kept to a minimum. In this way, a 1.5-mm-thin thermoplastic shell can be used as a formwork, without any additional support.

Geometries of different scales are tested in this article to evaluate the feasibility of the Eggshell fabrication process in an architectural context. An array of printing materials are also tested, and several different reinforcement concepts are analyzed.

The findings are used to produce a full-scale architectural demonstrator project. This article shows that a wide range of concrete geometries can be produced in a material-efficient fabrication process, paving the way toward mass customization and structural optimization within concrete architecture.

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