Enhancing Printable Concrete Thixotropy by High Shear Mixing

Abstract

Our results show that the storage elastic modulus as a function of time increases at a higher rate for the cement paste mixed at higher versus lower mixing intensity. Hence, higher mixing appears to be enhancing thixotropy. Using calorimetry analysis we find that higher mixing decreases the setting time and enhances the peak of the heat flow. By analyzing the nanoparticles present in the suspending fluid of the cement paste, we show, in accordance with literature, that an appropriate combination of mixing energy and super-plasticizer dosage promotes hydration by scratching hydrates from the surface of cement particles, stabilizing them in the suspending fluid and hence generating additional nucleation surfaces. These results open the door for the design of printing heads including high-shear micro mixers allowing for a faster liquid-to-solid transition of the printable material.

From analytical methods to numerical simulations: A process engineering toolbox for 3D concrete printing

“…It has, for example, been shown that the mechanical properties of cementitious materials depend on the energy of mixing [6,7]. Moreover, high-shear mixing can induce the crushing of solid particles, which can lead to enhanced structural build-up rates in the fresh state, thus proving useful in ensuring global stability of the printed system at early ages [8]. However, a high level of process control is required to enable this.…”