Concrete is one of the most consumed products in the world, with more than ten billion tonnes being produced every year. Optimising the use of concrete in prefabricated components can have a global impact in reducing material costs and the carbon footprint of buildings and infrastructure. However, optimisation algorithms often result in highly complex geometries which cannot be traditionally fabricated in concrete.
In order to overcome this limitation, binder-jet 3D-printing is used to fabricate the necessary formwork. The resulting sandstone formworks are suitable for casting concrete in any shape, regardless of geometric complexity. In order to reinforce such geometries, rigid bars are replaced with small steel fibres, six to ten millimetre long.
The demonstrator was developed through the SIMP (Solid Isotropic Modelling with Penalisation) topology optimisation algorithm of Simulia ABAQUS. The main goal of the optimisation process was to reduce material to a 0.18 set fraction of the initial volume while minimising the stress of the slab under uniform surface load. Boundary conditions were set to four simple supports located close to the corners. The 1.8 x 1 x 0.15 m design domain was discretised into 83,072 nodes with a volume of approximately 3.4 cm³ each.
The resulting design was fabricated using a nine millimetre thin 3D printed formwork, stabilised with a synthetic surface infiltration agent. Due to the optimised topology, the resulting concrete slab, weighing ~120 Kg, is 70 % lighter than a standard concrete solid slab covering the same area.
The project demonstrates a hybrid fabrication process in which a precious, smart fabrication process is used minimally, only where necessary, while the structural performance is provided by concrete, which is cast in a conventional manner. Digital fabrication is only used to produce a minor proportion of the final product, but has a major impact on its performance and behaviour.
