(565d) 2D-Stationary Computational Printing of Cement-Based Pastes.

The 3D printing of cement-based materials requires two primary paste characteristics: (1) extrudability, (2) resistance to deformation under layering load. To study the range of properties that effect printing outcomes, a computational strategy has been developed that captures the dynamics of 2D slices at a stationary location along the print path. It is well known that the rheology of cement paste is time-dependent and coupled to both the physical and chemical (hydration) behavior of cement particles. Thus, 3D printing of cement pastes is related to rheological (flow) characteristics of the material, e.g. yield stress, plastic viscosity, and time-dependent effects. To target optimal paste design parameters and correlate rheological properties to printability, this work introduces an efficient new computational printing strategy for predicting the flow behavior of cement pastes. A rheometer and a mini conical slum flow test were used to experimentally establish fluid properties and to calibrate rheological models prior to conducting computational experiments. The relative importance of rheological properties such as yield stress, and plastic viscosity were quantified and correlated with printed hollow cylinder benchmark objects. The layer height of printed objects was compared to 2D-stationary computational printing outcomes. Finally, based on the relationship of experimentally determined rheological measures of printing pastes to computational printing constructs, optimal rheological properties were suggested for scaling purposes.