Triaxial Compressive Behavior of 3D Printed PE-Fiber-Reinforced Ultra-High-Performance Concrete (2024-10)¶

The layered deposition process of 3D concrete printing can lead to reduced mechanical properties at the interfaces between filaments. To address this limitation, external confinement devices, such as fiber-reinforced polymer (FRP) wrapping, have been proposed to enhance the strength of 3D-printed concrete concrete. Achieving this requires a solid understanding of the triaxial mechanical performance of 3D-printed concrete. This study presents an experimental investigation of the triaxial compressive behavior of 3D-printed PE fiberreinforced ultra-high performance concrete (3DP-PEUHPC). A total of 16 pairs of concrete cubes were prepared, including mold-cast and 3D-printed specimens, and subjected to uniaxial and triaxial compression tests. The results revealed that the 3D-printed specimens exhibited either column-type or diagonal shear failures under triaxial compression. Weak bonding was observed at both filament-fusion and layer-fusion interfaces, with these weaker bonding interfaces, particularly when aligned parallel to the axial load, showing susceptibility to stress concentration and crack initiation. This led to a reduction in load-bearing capacity of the 3D-printed specimens compared to the mold-cast specimens. Importantly, as confining stresses increase, the difference in compressive strength between 3D-printed and mold-cast specimens decreases, highlighting the effectiveness of confinement in mitigating the directional weaknesses inherent in 3D-printed concrete. This paper also presents a modified model for predicting the axial stress-strain relationship of 3DP-PEUHPC under confinement, providing insights into the mechanism of FRP confinement on the compressive strength of 3D-printed concrete structures.