Identification of Reactive Aggregates Using Neutron Diffraction and Development of Methods to Reduce the Alkali-silica Reaction Expansion

摘要碱-硅反应（ASR）是由活性硅质骨料与高碱性混凝土孔隙溶液反应生成膨胀性碱硅酸盐凝胶，该凝胶可吸水膨胀。许多水坝、钢筋混凝土桥梁和路面都需要连续的维修或更换，因为这种有害反应会导致裂缝。多年来，人们对ASR引起的混凝土劣化进行了研究，但是，对这种膨胀的机制的理解仍然有限。该提案的目的是对导致ASR的岩石进行全面研究，然后开发减少这种膨胀的化学混合物。调查将在不同的尺度上进行，从分子到工程水平。理论模型将通过严格的实验研究进行验证，以定量表征岩石聚集体，其微观结构，以及由此产生的凝胶。洛斯阿拉莫斯国家实验室的飞行时间中子衍射装置将是研究岩石中矿物组分整体变形特性的一项重要技术。我们还将对这些岩石和混凝土样品进行化学和物理测试，以建立一种全面可靠的方法来识别混凝土结构的活性岩石。将研究新的化学外加剂以减少或消除混凝土中的膨胀。本研究成果将为集料和混凝土科学和工业提供重要信息。

Abstract The alkali-silica reaction (ASR) involves reactive siliceous aggregates and highly alkaline concrete pore solution producing an expansive alkalisilicate gel, which can imbibe water and then expand. Many dams, reinforced concrete bridges, and pavements require continuous repair or replacement because of cracks caused by this deleterious reaction. Concrete deterioration caused by the ASR has been investigated for many years, however, an understanding of the mechanisms underlying this expansion is still limited. The objective of this proposal is to establish a holistic study of the rocks that causes ASR and then develop chemical admixtures that reduce this expansion. The investigation will be done at various scales, from the molecular to the engineering level. The theoretical model will be validated through rigorous experimental research to quantitatively characterize rock aggregates, their microstructure, and the resulting gel. An important technique to study the bulk deformation properties of mineral components in rocks will be the time-of-flight neutron diffraction facilities at Los Alamos National Laboratory. We will also perform chemical and physical tests on these rocks and on concrete samples to establish a comprehensive and reliable methodology to identify reactive rocks for concrete structures. New chemical admixtures will be studied to reduce or eliminate the expansion in concrete. The results of this research will provide critical information for the aggregate and concrete science and industry.