A rheology-based quasi-static shape retention model for digitally fabricated concrete

The shape retention capability of an extruded filament is of cardinal importance for quality 3D printed concrete elements. Not only is it a prerequisite for surface aesthetics, but it also contributes towards buildability. Optimisation of filament layer height allows for construction time and cost saving possibilities. This research develops the theoretical framework for an analytical shape retention model that predicts the maximum stable filament layer height at which no plastic yielding occurs, based only on the rheology of a material. The Mohr-Coulomb failure criterion is employed and the model simplified by conservatively negating the effect of interparticle friction. A model is also developed that determines whether sufficient friction is present to induce confinement within a filament layer. An experimental verification process via filament extrusion confirms the applicability of the model. A 6.7% difference in stable filament layer height is obtained by comparison with a finite element analysis, proffering as numerical verification for the model. (C) 2020 Elsevier Ltd. All rights reserved.