Thixotropic structural build-up study for 3D concrete printing

Abstract

The novel development of 3D Concrete Printing (3DCP) technologies offers extraordinary advantages over conventional Building and Construction (B&C) practices. Its various benefits include an increase in architectural design flexibility, reduction of work-place safety hazards, elimination of unsustainable formworks and more. Yet despite the benefits, real-time 3DCP processes will demand a precise control over rheological/thixotropic structural build-up properties of the material at hand. This signifies a need for studies to be conducted, so as to provide critical insights on how different parameters (both printing and material) correlate with varying compositions of concrete admixture (e.g., accelerating agents and Superplasticizers). In this paper, innovative methods of material testing have been proposed, evaluated, and performed in an attempt to characterize deformative behavior and mechanical properties of freshly mixed cementitious mortar as a function of time. Contrary to the Bingham flow curve model [7], which characterizes visco-elasto-plastic fluids based on shear yield strength and plastic viscosity, this project aims to investigate vertical buildability rates of the concrete material via its compressive yield strength, so that relations can be identified for optimization of admixture selection. A series of compressive load tests have also been conducted to demonstrate the possibilities of simulation studies with 3DCP, which can potentially allow for early predictions of failure prior to large scale concrete printing.