Influence of concrete interfaces on the damage and pull-out behavior of 3D-printed concrete structures

Abstract

This research examines the pull-out behavior of steel reinforcement bars embedded within 3D-printed concrete (3DPC) specimens. A finite element model (FEM) incorporating cohesive elements was developed and validated through experimental data to assess the impact of printed concrete-to-concrete interfaces on the pull-out behavior of 3DPC. A detailed analysis of the interfaces’ influence on the 3D printed specimens revealed the peak load and slip behavior, failure mechanisms, and damage criteria. Additionally, a thorough investigation was conducted on how interfacial bond strength, layer and strip dimensions, print angle, and effective length of bond impact on pull-out behavior of 3DPC. The results reveal that 3DPC demonstrates reduced initial stiffness compared to cast specimens, maintaining consistent stiffness in both the X and Y directions. The mold-cast specimen demonstrates a 9.38 % higher load-bearing capacity than the interlayer 3D printed specimen and a 25 % higher load-bearing capacity than the interstrip 3D printed specimen. The percentage difference between the experimental and simulated results for these specimens is less than 5 %, indicating good agreement. The study shows that the peak load changes with the print angle, initially decreasing from 0° to 30° and then rising from 30° to 90°, with the maximum load occurring at 90°. Specimens printed at a 30° angle exhibit the highest damage due to increased stress concentrations, while those printed at 90° experience lowest damage because of more effective stress distribution. Additionally, increasing the layer size significantly enhances peak load capacity, with larger layers improving load distribution and structural support. Ultimately, specimens with a 50 mm bond length demonstrate the highest peak load and the lowest slip, indicating superior load-bearing capacity and bond performance. In contrast, shorter bond lengths result in lower peak loads and greater slip values. In conclusion, this study provides a foundation for future research on 3DPC modeling, particularly regarding concrete interfaces.