Zhao Yun-Chuan, Lei Hong-Gang, Guo Lang-Kuo, Lu Guo-Yun
College of Civil Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
School of Materials Science and Engineering, Tongji University, Shanghai 201804, China.
Materials (Basel). 2023 Feb 21;16(5):1766. doi: 10.3390/ma16051766.
Strengthening concrete structures with ultra-high performance concrete (UHPC) can both improve the bearing capacity of the original normal concrete (NC) structure and prolong the service life of the structure due to the high strength and durability of UHPC. The key to the synergistic work of the UHPC-strengthened layer and the original NC structures lies in the reliable bonding of their interfaces. In this research study, the shear performance of the UHPC-NC interface was investigated by the direct shear (push-out test) test method. The effects of different interface preparation methods (smoothing, chiseling, and planting straight and hooked rebars) and different aspect ratios of planted rebars on the failure mode and shear performance of the pushed-out specimens were studied. Seven groups of push-out specimens were tested. The results show that the interface preparation method can significantly affect the failure mode of the UHPC-NC interface, which is specifically divided into interface failure, planted rebar pull-out, and NC shear failure. The critical aspect ratio for the pull-out or anchorage of planted rebars in UHPC is around 2. The interface shear strength of straight-planted rebar interface preparation is significantly improved compared with that of the chiseled and smoothened interfaces, and as the embedding length of the planted rebar becomes longer, it first increases greatly and then tends to be stable when the rebar planted in UHPC is fully anchored. The shear stiffness of UHPC-NC increases with the increase of the aspect ratio of planted rebars. A design recommendation based on the experimental results is proposed. This research study supplements the theoretical basis of the interface design of UHPC-strengthened NC structures.
采用超高性能混凝土（UHPC）加固混凝土结构，既能提高原有普通混凝土（NC）结构的承载能力，又因UHPC的高强度和耐久性而延长结构的使用寿命。UHPC加固层与原有NC结构协同工作的关键在于它们界面的可靠粘结。在本研究中，通过直接剪切（推出试验）试验方法研究了UHPC-NC界面的抗剪性能。研究了不同界面处理方法（打磨、凿毛以及植直筋和弯钩筋）和不同植筋长径比对推出试件破坏模式和抗剪性能的影响。测试了七组推出试件。结果表明，界面处理方法能显著影响UHPC-NC界面的破坏模式，具体分为界面破坏、植筋拔出和NC剪切破坏。UHPC中植筋拔出或锚固的临界长径比约为2。直筋植筋界面处理的界面抗剪强度比凿毛和打磨界面有显著提高，且随着UHPC中植筋锚固长度的增加，其先大幅增加，在植筋完全锚固时趋于稳定。UHPC-NC的抗剪刚度随植筋长径比的增加而增大。基于试验结果提出了设计建议。本研究补充了UHPC加固NC结构界面设计的理论基础。
