A Rheological Model for Concrete Additive Manufacturing (2024-10)¶

The advent of 3D construction printing has ushered in a revolutionary era, demanding deeper insights into the understanding of cementitious fluid materials. Despite notable progress in additive manufacturing technologies, traditional rheological models (i.e., Bingham Plastic and Herschel-Bulkley) due to asymptotic behaviors of its plastic viscosity term fall short in describing the fluid mechanical properties of 3D printable concrete. This poses substantial challenges to achieving precise control and consistency in its boundless possibilities of mix design formulation. In this paper, we introduce an original rheological model that broadly characterizes the physiomechanical behaviours of non-Newtonian fluids, with a primary emphasis on thixotropic 3D printable cementitious pastes. Contrary to conventional representations, it is successfully demonstrated and validated herein that flow characteristics of 3D printable concrete may be described by two distinct viscosity terms, both of which collectively defines an upper and lower bound apparent viscosity with respect to a proposed activation function.