Abstract Concrete inherently contains pores and microcracks that can adversely impact its mechanical properties and long-term durability. However, characterising microcracks is difficult due to their complex, multiscale and three-dimensional (3D) nature. This paper presents an evaluation of 3D imaging techniques for characterising microcracks induced by different mechanisms. Seven cement pastes, mortars and concretes subjected to drying shrinkage, autogenous shrinkage and freeze-thaw cycles were investigated using focused ion beam nanotomography (FIB-nt), broad ion beam serial section tomography (BIB-SST), laser scanning confocal microscopy (LSCM) combined with serial sectioning and X-ray microtomography (μCT). The study shows that the characteristics of microcracks vary significantly depending on exposure conditions. Yet there is no single technique that can capture the entire size range of microcracks from sub to tens of μm within a sufficiently representative sampling volume. The achievable image volume and resolution, and the advantages and disadvantages of each technique are compared and discussed.

中文翻译：

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用于表征水泥基材料微裂纹的 3D 成像技术

摘要 混凝土固有地含有孔隙和微裂纹，会对混凝土的力学性能和长期耐久性产生不利影响。然而，由于微裂纹的复杂、多尺度和三维 (3D) 特性，很难对其进行表征。本文对用于表征由不同机制引起的微裂纹的 3D 成像技术进行了评估。使用聚焦离子束纳米断层扫描 (FIB-nt)、宽离子束连续断层扫描 (BIB-SST)、激光扫描共聚焦显微镜 (LSCM) 研究了七种水泥浆、砂浆和混凝土经受干燥收缩、自收缩和冻融循环) 结合连续切片和 X 射线显微断层扫描 (μCT)。研究表明，微裂纹的特征因暴露条件而异。然而，没有一种技术可以在足够具有代表性的采样体积内捕获从亚微米到数十微米的整个微裂纹尺寸范围。比较和讨论了可实现的图像体积和分辨率，以及每种技术的优缺点。