Multiscale modeling of ion transport and ASR induced damage in concrete structures
Multiscale modeling of ion transport and ASR induced damage in concrete structures
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DOI：
10.21012/fc10.234933
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发表时间：
2019-06
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影响因子：
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通讯作者：
T. Iskhakov
中科院分区：
文献类型：
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作者：
T. Iskhakov
碱-硅反应（ASR）是大坝、路面等混凝土结构中的一种有害膨胀反应，严重限制了其结构寿命。二氧化硅存在于所谓的“反应性”聚集体中，与孔隙流体中的钙、羟基和碱离子发生反应，形成亲水的碱-硅胶。凝胶填充集料和水泥浆中预先存在的微裂缝，并在水分存在的情况下膨胀。凝胶压力诱导的微裂纹扩展在宏观尺度上表现为膨胀。所谓的慢-晚ASR损伤机制始于骨料尺度，导致混凝土以微裂缝的形式退化，微裂缝从骨料开始，最终扩展到水泥浆体。为了预测混凝土路面的损伤和膨胀曲线，采用了多尺度方法。以线弹性断裂力学和微孔力学为特征的微裂纹过程通过平均场均匀化进行了放大。该模型还考虑了宏观尺度上完整和受损混凝土中的湿碱运移以及微观尺度上碱离子向骨料中的扩散，以解释外部碱和水分供应对混凝土路面耐久性的影响。通过与实验测量结果的比较，说明了多尺度化学力学模型在不同尺度下的能力。
Alkali-Silica Reaction (ASR) is a detrimental expansive reaction in concrete structures, such as dams and pavements, which substantially limits their structural lifetime. Silica present in the so-called ”reactive” aggregates reacts with calcium, hydroxyl and alkali ions of the pore fluid to form a hydrophilic alkali-silica gel. The gel fills pre-existing microcracks in the aggregates and the cement paste and swells in the presence of moisture. The gel pressure induced microcrack growth manifests itself as an expansion at the macroscale. The so-called slow-late ASR damage mechanism initiates at the aggregate scale, leading to concrete degradation in the form of microcracks, which starts in the aggregates and eventually propagates into the cement paste. In order to predict damage and expansion profiles in a concrete pavement a multiscale approach is adopted. The microcracking process that is characterized by linear elastic fracture mechanics and microporomechanics is upscaled by means of mean-field homogenization. Moisture and alkali transport in intact and damaged concrete at the macroscale as well as the diffusion of alkali ions into the aggregate at the microscale is also considered in the model to account for the influence of external alkali and moisture supply on the durability of concrete pavements. The capabilities of the multiscale chemo-mechanical model at different scales are illustrated by comparison with experimental measurements.