湿热-疲劳作用下水性环氧树脂桥梁混凝土裂缝演化

为探索湿热地区桥面板混凝土裂缝结构的演化规律，设计了湿热-疲劳耦合加载试验，借助扫描电子显微镜(scanning electron microscope, SEM)和Image-Pro Plus软件，分析了荷载单因素及湿热-疲劳耦合作用下桥面板混凝土裂缝结构参数的变化规律，揭示了混凝土细观裂缝的演化过程和水性环氧树脂混凝土的改性机理。结果表明：在荷载单场作用下，裂缝面积密度随作用次数单调增加，裂缝沿长度方向延伸和闭合交替变化，裂缝宽度则呈压缩和扩张交替变化；在湿热-疲劳耦合下，混凝土细观裂缝结构演化过程为压缩变形、扩展和贯通3个阶段。水性环氧树脂混凝土组裂缝面积密度、最大长度和宽度相比基准组分别降低了23.44%、33.19%和26%,分形维数减小了0.017。水性环氧树脂在混凝土内部形成的柔性聚合物膜桥联于微裂缝之间，能有效抑制混凝土细观裂缝的延伸与扩展，提高桥面混凝土耐久性。

Crack Evolution of Waterborne Epoxy Resin Modified Bridge Concrete under Hygrothermal Environment and Fatigue Load

In order to explore the evolution of the crack structure of bridge concrete in hygrothermal environment, a coupling test under hygrothermal environment and fatigue load was designed. With the help of scanning electron microscope(SEM) and Image-Pro Plus software, the changes in crack structure parameters of bridge concrete under the fatigue load, the hygrothermal environment and fatigue load were analyzed, which aimed to reveal the evolution process of concrete tiny cracks and the modified mechanism of waterborne epoxy bridge concrete. The results show that the crack area density increases with the number of load repetitions, the cracks extend and close alternately along the length direction, and the cracks compress and expand alternately along the width direction. The evolution of concrete tiny cracks under the coupling test is in three stages: compression deformation, extension, and penetration. Compared with the control group, the crack area density, maximum length, and width of the waterborne epoxy concrete are reduced by 23.44%, 33.19%, and 26%, respectively, and the fractal dimension is reduced by 0.017. The flexible polymer membranes formed by the waterborne epoxy resin inside the concrete bridges between tiny cracks, which can effectively restrain the extension and expansion of tiny cracks of concrete, and improve the durability of bridge concrete.