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Title: Microstructural Packing, Rheology, and Ram Extrusion Characteristics of 3-D-Printable Cementitious Binders

Author(s): Sooraj Nair, Aashay Arora, Hussam Alghamdi, Narayanan Neithalath

Publication: Web Session



Appears on pages(s):



Date: 10/15/2018

Cementitious binders amenable to extrusion and layered 3D printing are formulated by ensuring appropriate particle size distributions using fine limestone powder or a combination of limestone powder and microsilica or metakaolin. Mixtures were proportioned with and without a superplasticizer to enable different particle packings at similar printability levels. A microstructural packing coefficient, based on simulated fresh paste microstructure is defined, which is well-related to rotational and extensional rheological parameters of the pastes. This parameter is shown to be useful in selecting preliminary material combinations for layer-wise printable pastes. Extrusion rheology experiments, where the ram extruder is moved at different velocities and the corresponding extrusion force recorded, are used in conjunction with a phenomenological model to better understand extrusion printing of cementitious materials. The extensional yield stress and die wall slip shear stress extracted from the model, critical in extrusion-based 3D printing, show good correlation with microstructural packing.