Gravity induced flow to characterize rheological properties of printable cement-based materials

This paper presents testing methods based on the deformation and fracture of fresh cementitious materials only subjected to their own weight. These new methods are dedicated to the study of cementitious materials designed for 3D printing of concrete in order to verify rheological requirements related to the process. The first testing methods consists in measuring the tip deflection of a fresh cementitious materials, horizontally extruded, and allows for the determination of apparent elastic modulus of the material, while the second test consists in measuring the tensile strength of material filament leaving the nozzle of a vertical downward extruder. Both methods are based on the video capture of the deformation of the materials loaded by gravity, and provide results that are in agreement with tests performed with conventional testing machines (tensile and unconfined compression tests). This work shows the potential of the video capture of the gravity induced deformation of cementitious materials to describe behavior of cementitious materials at fresh state or for the in-line control of the 3D concrete printing process.

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