Effect of printing parameters in 3D concrete printing : printing region and support structures

Abstract

3D concrete printing can be used to build many complex structures. However, due to its material properties in the fresh state, it is difficult to construct overhanging structures without supports. In order to unleash the true capability of 3D concrete printing, a support structure is required to support any overhanging fresh material, which is usually removed during post-processing. This study demonstrates the feasibility of adjusting the printing parameters to print the main structure and support structure using a single type of building material. It was found that the solidity ratio, which is defined as the ratio between actual and expected filament sizes, was significantly affected by the nozzle travel speed and material volume flow rate. Furthermore, a gap distance characterisation test was carried out to find the maximum distance that the filament can cross over without a significant slump. The results were combined to determine the different printable regions for different operations. An overhang structure was printed to verify the results obtained for the different printing operations. This technique allows complex structure to be built without the need for human intervention throughout the printing process.