Steel-basalt hybrid fibers reinforced cementitious composite (SBFRCC) is a potential reinforcement and repair material for engineering structures with fire risk due to its excellent mechanical properties exposed to ambient and high temperatures. However, the bonding properties between SBFRCC and existing concrete are still unclear, especially at high temperatures. To fill this gap, the bonding properties between SBFRCC and existing concrete at high temperatures were investigated based on two situations by using the slant shear and splitting tensile tests. First, the existing concrete was heated at high temperatures and then bonded with SBFRCC and strengthening concrete to form combined systems, respectively. The effects of the interface roughness, high temperature duration, and post-fire-curing on their bonding properties were investigated. Second, the existing concrete was bonded with SBFRCC and then heated at high temperatures, and the effects of fly ash substation rates on the bonding properties were studied. Besides, the backscattered-electron (BSE) was used to observe the interface between the exiting concrete and SBFRCC exposed to various temperatures. Results show that the first bonded and then heated specimens are slide-failed and separated at the bonding interface from room temperature to 600 °C, while the damage is generated within the existing concrete at 800 °C. SBFRCC has better high temperature resistance than the existing concrete. The slant shear and splitting tensile strengths between PC-A and SBFRCC are 9%–33.3% higher than that of PC-A and strengthening concrete at all temperatures. The appropriate roughness at the interface by polishing can significantly improve the bonding properties between the existing concrete and SBFRCC. The bonding strength is recovered by more than 18.2% and 29.8% after the post-fire curing of 28 and 90 d, respectively. The increase of fly ash substitution rates has a certain contribution to the bonding properties above 600 °C.

钢-玄武岩混杂纤维增强水泥基复合材料（SBFRCC）由于其暴露于环境和高温下的优异机械性能，是具有火灾风险的工程结构的潜在加固和修复材料。然而，SBFRCC 与现有混凝土之间的粘结性能仍不清楚，尤其是在高温下。为了填补这一空白，基于两种情况，通过斜剪和劈裂拉伸试验研究了 SBFRCC 与既有混凝土在高温下的粘结性能。首先，将既有混凝土高温加热，然后分别与SBFRCC和加固混凝土粘结形成组合体系。研究了界面粗糙度、高温持续时间和火后固化对其粘合性能的影响。第二，现有混凝土与SBFRCC粘结，然后高温加热，研究了粉煤灰变率对粘结性能的影响。此外，背散射电子 (BSE) 用于观察暴露在不同温度下的现用混凝土和 SBFRCC 之间的界面。结果表明，从室温到 600 °C，先粘合后加热的试样在粘合界面发生滑动破坏和分离，而在 800 °C 时，损伤是在现有混凝土内部产生的。SBFRCC比现有混凝土具有更好的耐高温性能。在所有温度下，PC-A和SBFRCC的斜剪和劈裂抗拉强度比PC-A和加固混凝土高9%~33.3%。通过抛光在界面处适当的粗糙度可以显着改善现有混凝土与SBFRCC之间的粘结性能。经过28天和90天的火后养护，粘接强度分别恢复了18.2%和29.8%以上。粉煤灰替代率的提高对600℃以上的粘结性能有一定贡献。