Deformation-Based Buildability Assessment of 3D Printed Concrete and Its Numerical Simulation (2026-04)¶

Buildability of 3D printed concrete depends on the ability of previously deposited layers to sustain increasing self-weight during printing. This study used digital image correlation (DIC) to monitor vertical and out-of-plane displacements in 3D printed wall elements made with normal-weight and lightweight mortars, with and without steel fibers, at different times after mixing. A failure initiation height was defined from the point at which the displacement response deviated from its initial linear trend, allowing impending failure to be identified before visible collapse. Combined interpretation of vertical and out-of-plane displacement histories enabled distinction between plastic collapse and buckling-dominated failure. The normal-weight mortars showed plastic collapse at earlier printing times and transitioned to buckling-dominated failure with increasing time after mixing, whereas the lightweight mortars exhibited higher buildability and predominantly buckling-dominated failure. The addition of a small fiber volume slightly reduced buildability in the lightweight mixture. Finite element simulations using time-dependent elastoplastic material properties were used to interpret vertical deformation trends rather than predict failure height. The simulations agreed well with measured displacements for plastic-yielding cases but overpredicted vertical displacements in buckling-dominated cases because out-of-plane instability was not included. These results show that DIC-based displacement tracking provides a non-contact framework for assessing buildability, detecting failure initiation as an early warning signal before visible collapse, and interpreting fresh-state failure mechanisms in 3D printed concrete.