Shape stability of 3D printable concrete with river and manufactured sand characterized by squeeze flow

Abstract

Without formwork support, shape stability is one of the most critical properties of 3D printable concrete. This study evaluated the influence of the substitution of river sand by manufactured sand (0%, 15%, 25%, 35%, 50%, 75%, and 100% by volume) on the shape stability of freshly printed concrete. Shape stability was measured by squeeze flow tests with two different loading modes including an increasing force mode and a constant force mode. In the increasing force squeeze flow test, the elastic and plastic behaviors of mixtures were analyzed, while in the constant force squeeze flow test, modified yield stress was derived, with the consideration of the strength correction factor. Furthermore, two series of square wall layouts were printed and the failure patterns (either plastic collapse or elastic buckling) were well predicted by the squeeze flow. In addition, results demonstrated that the substitution of river sand by manufactured sand enhanced the shape stability of the 3D printable concrete, which closely related to the packing fraction of aggregate.