Abstract

One of the critical factors that govern the technology of concrete self-healing evaluation at laboratory scale is the crack induction pattern within the concrete sample. Within the various techniques of inducing artificial cracks, such as the flexural testing or splitting testing methods, there are limitations of inducing the microcracks homogenously throughout the entire volume of the concrete sample. In this study, an innovative technique is utilised to induce the microcracks at a controlled damage level to further study the self-healing phenomena in concrete at the laboratory scale. By placing a concrete sample into an ad-hoc fabricated steel mould and applying fractional compressive strength, the axial-circumferential pressure induces microcracks in the concrete sample, homogenously. A Finite Element Model was also built to investigate the hypothesis on the cracking pattern at various damage levels; jointly, experimental work was conducted with X-ray µCT images to reconstruct the three-dimensional sections at the various damage levels. Qualitative analyses in relation to the two test methods were conducted. Furthermore, quantitative analyses on the individual—artificially generated—cracks were conducted in terms of the crack size crack geometry variation and the orientation of the newly formed cracks. Results revealed that the proposed crack-inducing methodology is highly efficient to induce uniform cracks in the sample, assisting for the evaluation of concrete self-healing process. The novel method can be adapted to identify the optimised strategies for enhancing the structural performance of concrete, thus facilitating the safe operation of concrete infrastructure.

Graphic abstract

中文翻译：

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混凝土样品内部受控损伤方法的有限元-显微X射线耦合检查

摘要

在实验室规模上控制混凝土自我修复评估技术的关键因素之一是混凝土样品中的裂纹诱导模式。在各种诱导人工裂缝的技术中，例如挠曲测试或劈裂测试方法，存在在混凝土样品的整个体积中均匀地诱导微裂纹的局限性。在这项研究中，采用了一种创新技术来在可控的损伤水平下诱发微裂纹，从而进一步研究了实验室规模的混凝土中的自愈现象。通过将混凝土样品放入临时制造的钢模中并施加分数抗压强度，轴向周向压力会均匀地引起混凝土样品中的微裂纹。还建立了一个有限元模型来研究在不同损伤水平下裂纹模式的假设。共同地，用X射线µCT图像进行了实验工作，以重建各种损伤水平下的三维截面。相对于两种测试方法进行了定性分析。此外，根据裂纹尺寸，裂纹几何形状变化和新形成的裂纹的方向，对人工产生的裂纹进行了定量分析。结果表明，提出的裂纹诱导方法在样品中诱导均匀裂纹方面非常有效，有助于评估混凝土的自愈过程。可以采用这种新方法来确定用于增强混凝土结构性能的优化策略，

图形摘要