This study employed core specimens taken from a 24-year-old concrete bridge to investigate the ITZ spatial variation. As the lowest hardness component in the concrete, the ITZ was determined by height differences with other components caused by polishing. An automatic method for identifying the ITZ was developed based on 3D images with horizontal and vertical resolutions 1.75 μm and 0.41 μm, respectively. The thicknesses of ITZ and height differences between ITZ and mortar were statistically analysed, and a copula joint distribution model was established to describe these characteristics. The results showed that thicknesses at beam end and midspan were 47.62 μm and 42.95 μm, and height differences were 24.38 μm and 19.98 μm, respectively, indicating that the ITZ degradation in beam end was more severe. However, the correlation coefficients for the joint distribution at beam end and midspan were nearly identical (0.7197 and 0.7111, respectively), showing a relative stable relationship between the ITZ thickness and hardness.

中文翻译：

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使用 3D 图像扫描对老化桥梁混凝土界面过渡区进行空间变异分析


本研究采用取自一座已有 24 年历史的混凝土桥梁的核心样本来研究 ITZ 空间变化。作为混凝土中硬度最低的组分，ITZ是通过抛光引起的与其他组分的高度差来确定的。基于水平和垂直分辨率分别为 1.75 μm 和 0.41 μm 的 3D 图像开发了一种自动识别 ITZ 的方法。对ITZ的厚度以及ITZ与砂浆的高度差进行统计分析，并建立了一个copula联合分布模型来描述这些特征。结果表明，梁端和跨中厚度分别为47.62 μm和42.95 μm，高差分别为24.38 μm和19.98 μm，表明梁端ITZ退化较为严重。然而，梁端和跨中节点分布的相关系数几乎相同（分别为0.7197和0.7111），表明ITZ厚度和硬度之间存在相对稳定的关系。