Bond performance between FRP bars and 3D-printed high-performance concrete

Utilization of 3D-printed concrete (3DPC) in construction has drawn attention in recent years, while 3DPC is inherently subjected to weak structural integrity as the layer-by-layer stacking construction introduces deficiencies in concrete. Fiber-reinforced polymer (FRP) reinforcement which is flexible in shape has been proposed to be simultaneously printed with concrete so that the drawbacks of 3DPC are mitigated. In this study, the very important topic of bond performance between 3DPC and FRP bars are investigated. Totally 108 pull-out specimens were fabricated and the key variables included concrete strength, fibres volume fraction, bar direction, and anchorage length. The test results reveal that the failure pattern of the bond of 3DPC to FRP bars was similar to that of the mould-cast concrete specimens. However, the bond strength of the 3DPC specimens was lower. Results also reveal that the effect of concrete printing direction is evident, addition of fibre volume fraction has a negative impact on the bond strength, and the alter in concrete strength only slightly affect the bond strength. The bond-slip curves based on the modified mBPE model and CMR model can well predict the experimental curves.