Mineral composites: stay-in-place formwork for concrete using foam 3D printing

Abstract

Optimizing the shape of concrete construction elements is significant in reducing their material consumption and total weight while improving their functional performance. However, the resulting non-standard geometries are difficult and wasteful to fabricate with conventional formwork strategies. This paper presents the novel fabrication method of mineral foam 3D printing (F3DP) of bespoke lost formwork for non-standard, material-efficient, lightweight concrete elements. Many innovative formwork studies have shown that stay-in-place formwork can help to reduce waste and material consumption while adding functionality to building components. Foams are particularly suitable for this application because of their high strength-to-weight ratio, thermal resistance, and good machinability. F3DP allows the waste-free production of geometrically complex formwork elements without long lead times and production-specific tooling. This paper presents the material system and robotic F3DP setup with two experimental case studies: a perforated facade panel and an arched beam slab. Both cases use concrete as structural material and strategically placed custom-printed foam elements. In this first preliminary study, concrete savings of up to 50% and weight reduction of more than 60% could be achieved. This is competitive with standardized solutions such as hollow-core slabs but, in contrast, allows also for non-standard element geometries. Additional functionality, such as programmed perforation, acoustic absorption, and thermal insulation, could be added through the stay-in-place formwork. Moreover, the challenges and future developments of F3DP for sustainable building processes are discussed. Further studies are required to verify the findings. However, considering the urgent need for resource-efficient, low embodied-carbon solutions in the construction industry, this work is an important contribution to the next generation of high-performance building components.

Robotic 3D Printing of Geopolymer Foam for Lightweight and Insulating Building Elements

“…Several print path designs were developed in this research of F3DP with cement-free mineral foams for large-scale building elements with solid infill. 15 Direction-continuous spiral, contour-perpendicular zigzag, and alternating direction-parallel zigzag infill schemes were considered as options for the present study. However, to demonstrate the potential of this research for larger modular wall structures, the scale of printed elements had to be increased significantly while maintaining a low mass for lightweight manual assembly.…”

“… 14 Sintered mineral foams were utilized with F3DP to show their potential combined with concrete for facade and beam structures. 15 The energy-intensive sintering step could be omitted using set-on-demand geopolymer-hardened mineral foam to 3D print the functional stay-in-place formwork of a ribbed concrete slab prototype. 16 …”

Foamwork: Challenges and strategies in using mineral foam 3D printing for a lightweight composite concrete slab

“…This idea has already been researched in a pilot study using sintered mineral foams for a composite facade shading panel 7 and an arched beam floor system. 8 In the current study, the material and robotic fabrication system are improved. The fabrication of 24 freeform stay-in-place formwork components is demonstrated at higher precision due to the implementation of machine vision and 3D scanning.…”