Processing of Set-on-Demand Solutions for Digital Fabrication in Architecture (2019-09)¶

Digital fabrication with concrete holds potential to rationalize the production of large-scale mass-customized shapes in architecture. However, these digital technologies have manifold requirements for concrete compared to ordinary casting due to the relatively long production time combined with the need for fast strength build-up after placing. Thus, first, a large retarded batch of concrete is prepared to provide extended open time for fabrication. Then, the retarded concrete is accelerated on demand in small increments over the course of the experiment. This paper discusses suitable set on demand compositions to increase the buildability of three specific processes, Smart Dynamic Casting (SDC), Digital Casting (DC) and layered extrusion as they have similar requirements for concrete during fabrication. SDC and DC need low yield stress upon acceleration for casting and all three of them require consistent, rapid strength evolution for building. Two significantly different material compositions, a SCM and an UHPFRC are studied using two formulated accelerators. The overall hydration and strength build-up kinetics are investigated with calorimetry, slow penetration and uniaxial compression measurements. It was found that the rate of yield stress evolution can be customized with both mortars by using different dosages of accelerator and that the onset of strength build-up depends on the type of mortar formulation. The proposed acceleration method is a promising approach to increase the fabrication speed and the possible building height for a given mix design in applications like SDC, DC or layered extrusion.