Experimental and numerical study on the inter-layer shear behavior of 3D printed concrete

3D printing of concrete offers numerous advantages for the fabrication of architectural and structural components, such as cost-effectiveness, time savings, and enhanced quality. Although the potential of this technology has been widely demonstrated, it appears necessary to continue scientific research, as traditional testing methodologies for conventional concrete have been adapted to investigate phenomena of 3D printed concrete (3DPC) elements. This study aims to address this need by focusing on evaluating the inter-layer shear behavior of hardened 3DPC. A novel test method, adapted from masonry and concrete testing, was employed to conduct push-out tests on 3DPC specimens. The test set-up aims to induce shear forces along inter-layer surfaces under varying levels of normal compression (i.e., confining stress). The experimental results allowed the assessment of the shear behavior of the inter-layer surface in terms of interface shear strength, shear stiffness, cohesion, and friction angle. Additionally, non-linear finite element analyses (NLFEA) were conducted and validated against experimental results, providing valuable/effective tools for structural modeling of 3DPC elements. Both smeared crack and discrete crack approaches to non-linear fracture mechanics demonstrated good agreement with experimental observations. The comparison was effective regarding pre-peak and post-peak behavior, interface shear strength, cohesion, and friction angle.