Abstract The interfacial transition zone (ITZ) between cement paste and aggregates in concrete plays an important role in the macro-mechanical properties of concrete. It generally exhibits as a weak link, restricting the material resistance of concrete. The present work aims at proposing a numerical bridge from mesostructure features to macro-mechanical properties based on the extended finite element method (XFEM) and interfacial constitutive. For this end, first, a traction-separation constitutive reflecting the softening and dilatation behavior of ITZ is developed. Second, the two-phase configuration model, i.e., cement paste/aggregate with ITZ inserted as the interface, is adopted to characterize the concrete constituent distribution. Also, by using a unified framework of strong discontinuous displacement mode in XFEM, three states of ITZ, i.e., sticking, semi-separation and complete disengagement, can be captured naturally. Third, the elaborated XFEM approach for inclusion problem is verified by analyzing a plate with a single inclusion under tension, and the merits of the ITZ constitutive model are also verified by analyzing the traction and deformation evolution of ITZ suffering complex compression and shear. Finally, the approach is applied to investigate the effect of ITZ factors such as the initial stiffness, strength, and energy release rate on the macro-mechanical properties of concrete.

中文翻译：

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中尺度混凝土界面脱粘本构模型和XFEM模拟

摘要 混凝土中水泥浆体与骨料之间的界面过渡区（ITZ）对混凝土的宏观力学性能起着重要作用。它通常表现为薄弱环节，限制了混凝土的材料阻力。目前的工作旨在基于扩展有限元法 (XFEM) 和界面本构提出从细观结构特征到宏观力学特性的数值桥梁。为此，首先，开发了反映 ITZ 软化和膨胀行为的牵引分离本构。其次，采用两相配置模型，即以插入ITZ为界面的水泥浆体/集料，表征混凝土成分分布。此外，通过在 XFEM 中使用强不连续位移模式的统一框架，ITZ 的三种状态，即，粘、半分离、完全脱离，可自然捕捉。第三，通过分析受拉具有单个夹杂物的板来验证详细的 XFEM 方法来解决夹杂物问题，并通过分析受复杂压缩和剪切的 ITZ 的牵引和变形演化来验证 ITZ 本构模型的优点。最后，该方法用于研究初始刚度、强度和能量释放率等 ITZ 因素对混凝土宏观力学性能的影响。并通过分析受复杂压缩和剪切的ITZ的牵引和变形演化，验证了ITZ本构模型的优点。最后，该方法用于研究初始刚度、强度和能量释放率等 ITZ 因素对混凝土宏观力学性能的影响。并通过分析受复杂压缩和剪切的ITZ的牵引和变形演化，验证了ITZ本构模型的优点。最后，应用该方法研究初始刚度、强度和能量释放率等 ITZ 因素对混凝土宏观力学性能的影响。