Fast Complexity (2020-07)¶

Although slabs are major concrete consumers, they are mostly flat, oversized, monolithic boxes with significant embodied energy. The state of the art shows how computational design can lead to structurally efficient, lightweight, functionally integrated, and aesthetically accomplished slabs. However, these non-planar geometries are fabricated using complex formwork solutions involving multiple digital fabrication processes and manual concreting. This paper puts forward a novel fabrication method for the construction of materially lean concrete slab systems using two different Additive Manufacturing (AM) processes: Binder Jetted (BJ) formwork and 3D Concrete extrusion Printing (3DCP). A reusable formwork is fabricated first, using the BJ, and the loadbearing part of the slab element is then directly 3D-printed on top. This method combines the essential advantages of the two fabrication techniques: the high precision of BJ and the higher fabrication speed characteristic to 3DCP. The described 3DCP process uses a set on demand concrete that is activated inline, immediately before leaving the extruder-tool. A technical innovation is identified in dynamically varying the amount of activator for changing contour length.