3D concrete printing: A lower bound analytical model for buildability performance quantification

Concrete structures are 3D printed in the plastic state, therefore emphasis should be placed on the rheological characterisation of these materials to ensure that they are appropriate for 3D printing as well as for quality control. In this research, an analytical model based on the novel rheological characterisation of a material is presented as a method for quantifying the buildability performance of a 3D printable concrete/mortar. Structural instability of a freshly printed object e.g. elastic buckling is not accounted for as this model is only based on physical nonlinearity, in particular plastic yielding. The failure mechanism is based on the Mohr-Coulomb failure criterion, and incorporates Tresca and Rankine limit functions, dependent on the degree of confinement. The model is considered a lower bound theorem as stress redistribution occurs in the printed filament layers. The model is verified via an experimental study that yields a conservative error of < 10%.