Influence of print paths on mechanical properties and fracture propagation of 3D printed concrete

Abstract

When constructing concrete structures using 3D printing, it is important to consider the anisotropy due to the printing process. The print path influences the formation of layer interfaces and inter-filament voids, and the fracture propagation behavior of the printed specimen. In this paper, the fracture propagation behavior of printed mortar specimens under compressive, tensile, and bending stresses is evaluated for different print paths. X-ray computed tomography visualizes the interior of printed specimens and shows that the pressure during material extrusion elongates the intra-filament voids. The inter-filament void structure is influenced by the print path, forming an aligned structure in one direction or a complex lattice-like structure. Anisotropy in the deformation direction under compressive stress, which is influenced by the inter-filament void structure, is assessed by 3D scanning. Under tensile stress, Digital Image Correlation (DIC) visualizes that tensile stress is concentrated in the layer interface, causing cracks to propagate along the layer interface. Under bending stress, DIC evaluates the effect of the print path on fracture propagation behavior. The results show that the mechanical properties and fracture propagation behavior of printed specimens are affected by the arrangement of the layer interface and inter-filament void, which is governed by the print path. (200 words)