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 totalweight while improving their functional performance. However, the resulting non-standard geometries are difficult andwasteful to fabricate with conventional formwork strategies. This paper presents the novel fabrication method of mineralfoam 3D printing (F3DP) of bespoke lost formwork for non-standard, material-efficient, lightweight concrete elements. Manyinnovative formwork studies have shown that stay-in-place formwork can help to reduce waste and material consumptionwhile adding functionality to building components. Foams are particularly suitable for this application because of their highstrength-to-weight ratio, thermal resistance, and good machinability. F3DP allows the waste-free production of geometricallycomplex formwork elements without long lead times and production-specific tooling. This paper presents the materialsystem and robotic F3DP setup with two experimental case studies: a perforated facade panel and an arched beam slab. Bothcases use concrete as structural material and strategically placed custom-printed foam elements. In this first preliminarystudy, concrete savings of up to 50% and weight reduction of more than 60% could be achieved. This is competitive withstandardized solutions such as hollow-core slabs but, in contrast, allows also for non-standard element geometries. Additionalfunctionality, such as programmed perforation, acoustic absorption, and thermal insulation, could be added through thestay-in-place formwork. Moreover, the challenges and future developments of F3DP for sustainable building processes arediscussed. 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 ofhigh-performance building components.