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.

该项目的目的是将硅酸钙（C-S-H）的化学成分和分子结构与材料的粘弹性机械性能联系起来。 C-S-H是控制混凝土特性的波特兰水泥的主要结合水合产物。如果在生产C-S-H期间可用氧化铝（通常来自铝硅酸盐补充胶结材料），C-S-H能够将铝掺入作为宾客离子，从而产生钙铝硅酸盐水合物（C-A-S-H）。氧化铝融合可以通过增加四面体链长的长度来改变其分子结构，这种变化可在C-S-H层之间促进交联。通过应用多尺度的静态和动态机械测试，其中包括一种新型的纳米力学特征技术，动态纳米识别技术将在该项目期间进行测试的主要假设是确定C-A-S-H的粘弹性是否比C-S-H低于C-S-H，因为这种增加的聚合增加了。为了将化学成分和分子结构与粘弹性特性相关联，在实验室中，相纯的C-S-H和C-A-S-H将通过不同的组合物合成，并使用先进的技术（例如核磁共振）（NMR）来表征局部原子环境，X射线衍射（XRD），以检测Crystalline Complase for Crystalline Chopase for Bulase Cropersction（X-Rayscement）和X-Rayscressction（X-Rayscress和X-ray flycressction）。此外，机械测试之前和之后的NMR表征的组合将表明在粘弹性变形过程中分子结构是否有任何变化，知识将是变化的。混凝土是世界上使用最广泛的建筑材料，其生产与大约5％的全球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减少产生的混凝土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，它也可以减少混凝土中的波特兰水泥含量，从而减少其温室气体排放。这项研究与教育计划充分融合，包括（a）多尺度培训材料的高级化学机械特征的研究生，（b）将研究结果纳入研究生级别的课程，以及（c）在才华横溢的中学生中对工程和可持续建筑产生热情。