Effect of Printing Parameters on Print Quality and Fracture Propagation Behavior of 3D Printed Concrete

3D concrete printing, an additive manufacturing technology using cementitious materials for large-scale structures, has received a lot of attention recently. 3DCP offers many advantages, including material savings, labor efficiency, and increased flexibility in structural modeling. However, despite the extrusion of carefully designed materials to build the structure, the layered filament system unavoidably creates layer interfaces and inter-filament voids. When manufacturing 3D printed concrete, the method of fabrication, printing parameters, e.g. nozzle geometry and extrusion speed, need to be taken into account. The influence of the printing parameters that determine the arrangement of the layer interfaces in printed concrete, i.e., the print paths, on the fracture propagation behavior of printed specimens has hardly been investigated. Moreover, few studies have adequately assessed the internal structure and print quality of printed concrete using non-destructive testing methods. Mechanical fracture at the layer interface, which is a minute region in printed specimens, was evaluated using acoustic emission techniques in this study. Also, the applicability of elastic wave tomography was investigated for evaluating internal quality. The results show that AE activity during bending failure reveals the influence of the layer interface arrangement of the printed specimen on its fracture propagation behavior. Additionally, elastic wave tomography visualizes the internal structure of printed specimens with different inter-filament void structures, achieved by varying the extrusion volume.