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 fiber-reinforced 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.

中文翻译：

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3D 打印 PE 纤维增强超高性能混凝土的三轴受压行为


3D 混凝土打印的分层沉积工艺会导致细丝之间界面的机械性能降低。为了解决这一限制，已经提出了外部约束装置，例如纤维增强聚合物 （FRP） 包裹，以提高 3D 打印混凝土的强度。要实现这一目标，需要对 3D 打印混凝土的三轴力学性能有深入的了解。本研究对 3D 打印 PE 纤维增强超高性能混凝土 （3DP-PEUHPC） 的三轴压缩行为进行了实验研究。总共制备了 16 对混凝土立方体，包括模铸和 3D 打印试样，并进行了单轴和三轴压缩试验。结果表明，3D 打印试样在三轴压缩下表现出柱式或对角线剪切破坏。在细丝-熔合和层-熔合界面处都观察到弱粘合，这些较弱的粘合界面，特别是当平行于轴向载荷对齐时，表现出对应力集中和裂纹萌生的敏感性。与模铸试样相比，这导致 3D 打印试样的承载能力降低。重要的是，随着围压应力的增加，3D 打印和模铸试样之间的抗压强度差异减小，凸显了约束在减轻 3D 打印混凝土固有的方向弱点方面的有效性。本文还提出了一种改进的模型，用于预测约束下 3DP-PEUHPC 的轴向应力-应变关系，为 FRP 约束对 3D 打印混凝土结构抗压强度的机制提供了见解。