This study presents a homogenization approach to understand and simulate the heterogeneous expansion of irregularly shaped aggregate induced by alkali-silica reaction (ASR). The analysis employs a cubic representative volume element (RVE) containing a single reactive aggregate with an arbitrary shape embedded in a mortar matrix. At the aggregate level, ASR expansion is characterized by applying a homogeneous volumetric strain inside the internal structure of the reactive aggregate based on a first-order reaction kinetics. On the RVE scale, ASR expansion is formulated as a series of diffusion processes involving the formation of ASR products and their resulting expansion. By discretizing the RVE, a homogenization approach was proposed to link the homogeneous expansion rate at the aggregate level with the heterogeneous expansion strain at the RVE level. The model captures the heterogeneity of ASR expansion produced by reactive aggregate with arbitrary geometries by assigning anisotropic expansion capacity in different directions as a function of aggregate volume and size. The model was calibrated and validated using experimental data from literature. Results demonstrate that ASR expansion increases with aggregate size in the expansion direction for a given aggregate volume, and also with overall aggregate volume for a constant aggregate size in expansion direction. In addition, the simulations show that ASR-induced cracks in the mortar matrix initially form around the surface of reactive aggregate, particularly along the major axis (the direction of the maximum aggregate length) and around sharp corners of the irregularly shaped aggregate.

中文翻译：

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碱-二氧化硅反应诱导的不规则形状聚集体膨胀：来自数值建模的见解


本研究提出了一种均质化方法来理解和模拟碱-二氧化硅反应 （ASR） 诱导的不规则形状聚集体的非均质膨胀。该分析采用立方代表体积单元 （RVE），其中包含嵌入砂浆基质中具有任意形状的单个反应性骨料。在聚集体水平上，ASR 膨胀的特征是基于一级反应动力学在反应聚集体的内部结构内施加均匀的体积应变。在 RVE 尺度上，ASR 膨胀被表述为一系列扩散过程，涉及 ASR 产物的形成及其由此产生的膨胀。通过离散 RVE，提出了一种均质化方法，将聚集体水平的均质膨胀速率与 RVE 水平的异质膨胀应变联系起来。该模型通过将不同方向的各向异性膨胀容量分配为骨料体积和大小的函数，捕获了具有任意几何形状的反应性骨料产生的 ASR 膨胀的异质性。该模型使用文献中的实验数据进行了校准和验证。结果表明，对于给定的聚合卷，ASR 扩展随扩展方向的聚合大小而增加，对于扩展方向的恒定聚合大小，ASR 扩展也随总聚合卷的增加而增加。此外，模拟表明，ASR 诱导的砂浆基体裂缝最初在反应骨料表面周围形成，特别是沿长轴（最大骨料长度的方向）和不规则形状骨料的尖角周围。