预制键槽UHPC-混凝土界面黏结性能研究

UHPC永久性模板与普通混凝土的界面黏结性能是两者协同作用的关键,研究不同键槽类型、混凝土强度和养护条件等因素对UHPC-混凝土界面黏结性能的影响。结果表明:键槽可以提高UHPC-NC界面黏结强度,其中B型键槽机械联锁作用贡献最大。劈裂拉伸试件界面中心轴线的应变大于两侧应变,界面裂缝从水平拉应变开始向压应变区域扩张。复合试件键槽的存在使得裂缝在混凝土内部由一端延伸至另一端,并非两端向内发展。随着后浇混凝土抗压强度的提高,界面劈裂抗拉强度增幅降低。蒸汽养护导致初始收缩变形较大,应力集中区域比标准养护试件更大。复合试件界面劈裂抗拉强度可以通过混凝土立方体抗压强度和拟合参数c计算得出。提出了最优永久性模板键槽参数和养护条件。

Study on Bonding Performance of the Interface Between Precast Keyway UHPC and Post-cast Normal Concrete

The interfacial bonding performance between ultra-high performance concrete(UHPC) permanent template and ordinary concrete (NC) is the key to their synergistic effect. The effects of diffe-rent keyway types, concrete strength, and curing conditions on the interfacial bonding performance of UHPC-NC were studied. The results indicate that keyway can improve the bonding strength of UHPC-NC interface, with B-type keyway mechanical interlocking contributing the most. The strain of the central axis of the interface of the splitting tensile specimen is greater than that of the two sides, and the interface crack expands from the horizontal tensile strain to the compressive strain region. The existence of keyways in composite specimens causes cracks to extend from one end to the other inside the concrete, rather than developing inward from both ends. As the compressive strength of post poured concrete increases, the increase rate of the interfacial splitting tensile strength decreases. Steam curing specimens result in a larger initial shrinkage deformation and a larger stress concentration area than standard curing specimens. The interfacial splitting tensile strength of composite specimens can be calculated from the compressive strength of concrete cubes and the fitting parameter c. The optimal permanent template keyway parameters and maintenance conditions are proposed.