The Effect of Alumina Substitution on Viscoelasticity of Calcium Silicate Hydrate

氧化铝替代对水合硅酸钙粘弹性的影响

• 批准号: 1300917
• 负责人: Paramita Mondal
• 金额: $ 30万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1300917&HistoricalAwards=false
• 关键词: Effect; Alumina; Substitution; Viscoelasticity; Calcium

The objective of this project is to link the chemical composition and molecular structure of calcium silicate hydrate (C-S-H) to the viscoelastic mechanical properties of the material. C-S-H is the main binding hydration product of portland cement that governs properties of concrete. If alumina is available during the production of C-S-H, typically from alumino-silicate supplementary cementitious materials, C-S-H is able to incorporate aluminum as a guest ion, producing a calcium aluminosilicate hydrate (C-A-S-H). Alumina incorporation is seen to alter its molecular structure by increasing the tetrahedral chain length, a change that is seen to promote crosslinking between C-S-H layers. By applying a multiscale static and dynamic mechanical testing that include a novel nanomechanical characterization technique of dynamic nanoindentation, the main hypothesis that will be tested during this project is to determine whether C-A-S-H is less viscoelastic than C-S-H due to this increased polymerization. To relate chemical composition and molecular structure with viscoelastic properties, phase-pure C-S-H and C-A-S-H will be synthesized in the lab with varying composition and characterized using advanced techniques such as nuclear magnetic resonance (NMR) for local atomic environment, X-ray diffraction (XRD) for detection of crystalline phases, and X-ray fluorescence (XRF) for bulk chemical composition. Furthermore, a combination of NMR characterization before and after mechanical testing will indicate if there are any changes in molecular structure during viscoelastic deformation, knowledge that will be transformative.If the hypothesis that alumina substitution in C-S-H reduces creep is proved right, this research will lead to a new method of controlling the viscoelasticity of concrete that can ultimately lead to longer life of concrete structures. Concrete is the most widely used construction material in the world and production of it is associated with approximately 5% of the global CO2 emissions. Thus, any increase in the longevity of concrete structure will mean reduction in the amount of concrete produced and associated greenhouse gas emission. In addition, the main source of alumina in C-S-H is usually fly ash, a waste material that also reduces the portland cement content in concrete and thereby reduces its greenhouse gas emission. The research is well integrated with educational plans, including (a) training graduate student in advanced chemo-mechanical characterization of materials at multiscale, (b) incorporating research findings into graduate level classes, and (c) generating enthusiasm for engineering and sustainable construction among talented middle school students.

本项目的目的是将水合硅酸钙（C-S-H）的化学组成和分子结构与材料的粘弹性力学性能联系起来。C-S-H是波特兰水泥的主要粘结水化产物，控制混凝土的性能。如果在C-S-H的生产过程中氧化铝是可用的，通常来自铝硅酸盐补充胶凝材料，则C-S-H能够掺入铝作为客体离子，产生水合铝硅酸钙（C-A-S-H）。氧化铝掺入被认为是通过增加四面体链长来改变其分子结构，这种变化被认为是促进C-S-H层之间的交联。通过应用多尺度静态和动态力学测试，其中包括一种新的纳米力学表征技术的动态纳米压痕，主要假设，将在这个项目中进行测试，以确定是否C-A-S-H是较低的粘弹性比C-S-H由于这种增加的聚合。为了将化学组成和分子结构与粘弹性联系起来，将在实验室中合成具有不同组成的纯相C-S-H和C-A-S-H，并使用先进技术进行表征，例如用于局部原子环境的核磁共振（NMR），用于检测结晶相的X射线衍射（XRD）和用于本体化学组成的X射线荧光（XRF）。此外，力学测试前后的核磁共振表征组合将表明粘弹变形过程中分子结构是否发生任何变化，这将是变革性的知识。如果C-S-H中氧化铝替代降低蠕变的假设被证明是正确的，这项研究将带来一种控制混凝土粘弹性的新方法，最终可以延长混凝土结构的使用寿命。混凝土是世界上使用最广泛的建筑材料，其生产与全球约5%的二氧化碳排放量有关。因此，混凝土结构寿命的任何增加都意味着混凝土生产量和相关温室气体排放量的减少。此外，C-S-H中氧化铝的主要来源通常是粉煤灰，这是一种废料，也减少了混凝土中的波特兰水泥含量，从而减少了其温室气体排放。该研究与教育计划很好地结合在一起，包括（a）培养研究生在多尺度材料的高级化学机械表征，（B）将研究成果纳入研究生水平的课程，以及（c）在有才华的中学生中产生对工程和可持续建设的热情。