Abstract

This paper describes how 3D-printed formwork can be used to facilitate the integration of functional features in structurally optimised concrete slabs. The weight of concrete slabs represents the largest portion of the weight of a concrete framed, multi-storey building. Despite this significant share, slabs are usually designed as monolithic, oversized boxes due to various construction constraints. Optimised design alternatives, featuring funicular shapes, differentiated ribs, profiled soffits and hollow sections use significantly less material and can moreover integrate building services within the thickness of the slab, such as heating, cooling and ventilation. Nevertheless, both the optimised external geometry and the internal network of functional voids present very complex fabrication challenges for concrete. This is because standard commercial formwork systems are not suitable for bespoke designs. To address this limitation, this research demonstrates how fused-deposition 3D printing can be used for the fabrication of custom formwork for a functionally integrated concrete slab. The resulting prototype efficiently uses material and integrates provisions for an active beam ventilation system within the standard structural depth of the slab (Fig. 1). All these intricate geometric features are achieved with an ultra-lightweight 3D-printed formwork, which weighs less than 15 kg for the 660 kg concrete slab.