Experimental Characterization and Theoretical Modeling of the Bonding Behavior Between FRP Bars and 3D Printed Strain-Hardening Cementitious Composites (2026-02)¶

3D printed strain-hardening cementitious composites (3DP-SHCC) have become a hotspot in engineering structures due to the excellent toughness and high-efficiency construction, while the bonding behavior between 3DP-SHCC and FRP bars remains unclear. In this study, a systematic pull-out test is designed and conducted to investigate the effects of FRP bar types (i.e., basalt, carbon, and glass FRP bars) and placement directions on the anisotropic reinforcement bonding properties of 3DP-SHCC under the given FRP bar diameter and anchorage length, putting an emphasis on the failure patterns, bond stress-slip curves, and bonding strength. The results suggest that although the failure patterns have minor variation with FRP type and placement direction, there are significant differences in the damage morphology and formation mechanism of the bonded interfaces of the three types of FRP bars. Moreover, the carbon FRP bars perform the best bonding behavior with 3DP-SHCC, with the X- and Y-direction bonding strength being 16.70 and 15.71 MPa, respectively, which are only about 10% lower than that of the steel rebars. In contrast, the bonding strength of glass FRP bars is only around 24.01–26.00% of the basalt FRP bars within the measured placement directions, partly owing to the relatively round geometry of glass FRP bars. Based on the thick-walled cylinder model, a novel bond-slip constitutive model is proposed to predict the bonding behavior of FRP bars in 3DP-SHCC, the predictions of which match well with experimental results.