Influence of External Vibration on the Gravitational Flow Characteristics of Cementitious Materials (2022-03)¶

Three-dimensional (3D) printable concretes require high plastic yield stress to retain the shape of the printed layers, however, to enhance the ease of pumping the cementitious system should have as low a plastic yield stress as possible. To address these opposing needs for printing and pumping, a vibration-based active rheology-controlled system which temporarily reduces the plastic yield stress during pumping has been designed. To study the response of the rheological properties of the cementitious system and its response to vibrations, a test setup which can simulate the vibration that occurs during pumping has been developed. An EN445 flow cone was modified by mounting a frequency-controlled vibration setup. The effect of vibration on the flow initiation, flow topology, and flow rate of cementitious systems with three different water-to-binder ratios, two pozzolans (silica fume and metakaolin), and multiple dosage levels of high-range water reducer and viscosity modifying agents was studied. Results from this study suggest a strong correlation between plastic yield stress, and the frequency and amplitude of vibration with implications for 3D printing.