Analysis of anisotropic behavior in 3D concrete printing for mechanical property evaluation

The rapid expansion of automated construction methods is pivotal in meeting the burgeoning demand for housing. However, ensuring these methods comply with design codes and regulatory standards requires a deep understanding of the material design process. In addition, the use of lightweight concrete is essential in 3D Concrete Printing (3DCP) to reduce the significant weight of printed structures while understanding the strength and behavior of these materials. There are concerns about the layer-by-layer deposition of concrete during printing, as weaker bonding between layers may undermine structural integrity. This study explores the anisotropic behavior of concrete and its impact on mechanical properties. Samples extracted from printed blocks were tested in various orientations, including comparisons with LWC containing Expanded Polystyrene (EPS). The mixtures were selected to evaluate the impact of lightweight aggregates on anisotropic behavior and compare them to normal-weight concrete. The results demonstrate that the timing between layer depositions significantly influences strength. Notably, cracks observed between filaments indicate weaker interlayer bonding, a condition exacerbated by delays between printing each layer, which notably affects flexural and shear strengths. These findings highlight that such delays increase the anisotropic coefficient, underscoring the importance of meticulous attention during the design process. A micro-model was utilized to analyze the 3DCP in detail, employing the Concrete Damage Plasticity (CDP) and interaction-separation law in Abaqus. The numerical analysis exhibited a strong correlation with experimental tests.