Evaluation of Early-Age Concrete Structural Build-Up for 3D Concrete Printing by Oscillatory Rheometry

This paper addresses the material buildability challenge in extrusion-based 3D Concrete Printing (3DCP) applications, since this is paramount to increase production rates of vertical elements such as columns. We utilized oscillatory rheology to determine the early-age structural build-up curves of 3DCP mixes comprising White Ordinary Portland Cement (OPC), Calcium Aluminate Cement (CAC), limestone filler, sand, viscosity modifying agent, retarder, and a plasticizer. Such curves served as basis to verify whether a geometry is printable, allowing for tuning the printing process parameters. The material characterization approach is validated through a case study, in which a column was designed – defining the structural build-up requirements – and printed using a robot-based 3DCP at a 0.68 m/h vertical build rate. Such case study and lessons thereof provide valuable insights into the link between design, material properties and 3DCP process parameters, setting the basis for a comprehensive study on the early-age structural build-up measurements to support 3DCP mix design.