Alkali‐silica reaction (ASR) causes severe degradation of concrete. The mechanical property of the ASR product is fundamental to the multiscale modeling of concrete behavior over the long term. Despite years of study, there is a lack of consensus regarding the structure and elastic modulus of the ASR product. Here, ASR products from both degraded field infrastructures and laboratory synthesis were investigated using high‐pressure X‐ray diffraction. The results unveiled the multiphase and metastable nature of ASR products from the field. The dominant phase undergoes permanent phase change via collapsing of the interlayer region and in‐planar glide of the main layer, under pressure >2 GPa. The bulk moduli of the low‐ and high‐pressure polymorphs are 27±3 and 46±3 GPa, respectively. The laboratory‐synthesized sample and the minor phase in the field samples undergo no changes of phase during compression. Their bulk moduli are 35±2 and 76±4 GPa, respectively. The results provide the first atomistic‐scale measurement of the mechanical property of crystalline ASR products.

中文翻译：

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静水压缩下碱硅反应产物的力学行为和相变。

碱二氧化硅反应（ASR）导致混凝土严重降解。从长远来看，ASR产品的机械性能对于混凝土行为的多尺度建模至关重要。尽管进行了多年的研究，但关于ASR产品的结构和弹性模量仍缺乏共识。在这里，我们使用高压X射线衍射研究了降解现场基础设施和实验室合成的ASR产品。结果揭示了该领域ASR产品的多相和亚稳态性质。在> 2 GPa的压力下，主相通过中间层的塌陷和主层的平面滑移而发生永久性相变。低压和高压多晶型的体模分别为27±3 GPa和46±3 GPa。实验室合成的样品和田间样品中的次要相在压缩过程中不会发生相变。它们的体积模量分别为35±2 GPa和76±4 GPa。结果提供了对晶体ASR产品力学性能的首次原子尺度测量。