3D Printed Recyclable Sand Formworks: A Zero‐Waste Path for Lightweight Concrete Structures

Abstract On the path to a sustainable transformation of the built environment, the concrete industry requires solutions that integrate mass customization with rigorous resource efficiency. This paper presents the results of SPP 2187 Subproject 12, which focuses on the development of an automated, zero‐waste formwork production cycle for complex lightweight concrete components. The technology utilizes Selective Binder Activation (SBA)—a powder‐bed‐based additive manufacturing process—to create water‐soluble sand formworks from a mixture of silica sand and organic binder. Key developments include a large‐scale 3D printing unit, a transparent CAD‐to‐machine‐code computational workflow, and a robust material reclamation strategy that enables near‐complete recycling of the formwork material. The technology's scalability and structural viability are validated through two prototypes: a 1.2 m functionally graded reinforced concrete beam and the Marinaressa Coral Tree, a 3.2 m tall architectural demonstrator exhibited at the 2023 Venice Architecture Biennale. The results demonstrate that this circular manufacturing approach can reduce concrete consumption by 60% while eliminating formwork waste during production and reach a production output of 34 l/h, effectively placing it within the performance range of current industrial standards.