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Towards the Formulation of Robust and Sustainable Cementitious Binders for 3-D Additive Construction by Extrusion

Published

Author(s)

Dale P. Bentz, Scott Z. Jones, Isaiah R. Bentz, Max A. Peltz

Abstract

Additive construction by extrusion (ACE), also known as 3-D printing, is becoming a new paradigm for concrete construction. While significant cost and manpower savings are projected, many issues remain to be solved before ACE can be viewed as a mainstream technology. Among these is the formulation of a robust and sustainable binder that meets the demanding rheological and mechanical performance requirements of an ACE application. This paper investigates the development of such a binder by exploring binary blends of cement with limestone powder at various proportions, supplemented with the incorporation of a retarder/accelerator admixture combination. Performance is chiefly characterized by applying a Bingham fluid model to characterize the rheological parameters of yield stress and plastic viscosity and by assessing hydration via isothermal calorimetry measurements. Matching the surface area of the limestone powder to that of the cement that it is replacing affords the opportunity to regulate rheology via water content adjustments, while engineering the cement:limestone powder ratio to provide the desired mechanical properties. The utilization of the retarder/accelerator combination produces a paste with a long pot life (stable rheology) that can be quickly stiffened via the injection of the accelerator (and retarded paste) into a static mixer just prior to the printer’s exit nozzle. Thus, these pastes demonstrate the potential to provide a robust and sustainable binder for ACE applications.
Citation
Construction and Building Materials
Volume
175

Keywords

3-D printing, accelerator, additive construction by extrusion, hydration, isothermal calorimetry, open time, retarder, rheology
Created April 30, 2018, Updated November 10, 2018