Characterizing Paste Microstructure during Setting with Combined Raman Spectroscopy and Confocal Microscopy

本课题的研究目标是利用先进的物理和化学成像方法，探索水泥颗粒的分散、团聚和渗透机理，从微观结构层面提高对水泥凝结的认识。为了实现这一目标，拉曼光谱结合共聚焦显微镜将在新鲜水泥体上实时进行。首先将拉曼光谱应用于干水泥粉末和新鲜水泥体，以追踪早期水化过程中化学成分的变化。将开发熟料相和水化产物的拉曼文库。然后，将拉曼光谱与共聚焦显微镜相结合，对颗粒的物理分散和化学分散（化学成图）进行实时观察，研究化学成分和表面化学对颗粒絮凝的影响。物理和化学微观结构参数将使用移动窗口建模方法与凝结时间和水化热特征相关联。凝结硬化过程是混凝土结构最关键的时期，混凝土的化学、物理和机械性能在此期间发生快速变化。设置后不能进行混音、重铸或替换。因此，对混凝土的凝结特性有扎实的了解是保证材料质量和性能的必要条件。混凝土凝结是由水泥颗粒的分布、运动和连接引起的浆料凝结控制的。通过对初始水化阶段颗粒絮凝、团聚和渗透过程的现场观察，可以对膏体凝结行为有基本的认识，从而对混凝土施工过程进行控制。通过结合拉曼光谱和共聚焦显微镜，这项拟议的工作将建立一个早期水化的数据库，这将对混凝土工业，特别是化学外加剂公司有用。该数据库也将对水化/微观结构发展模型有用。教育计划注重培养本科生和研究生更好的批判性思维和研究能力。此外，还计划针对少数民族和女学生等不同群体的K-12学生开展“INSPIRE”、“E-Expo”等活动。

The research goal of this project is to enhance our knowledge of cement setting on microstructural level by exploring the dispersion, agglomeration and percolation mechanism of cement particles with advanced physical and chemical imaging methods. To achieve this goal, Raman spectroscopy combined with confocal microscopy will be conducted in real-time on fresh cement pastes. Raman spectroscopy will firstly be applied to both dry cement powder and fresh paste to trace changes in the chemical compositions during early hydration. A Raman library of clinker phases and hydration products will be developed. Then, the Raman spectroscopy will be combined with confocal microscopy to conduct real-time observation on the physical dispersion of particles together with chemical dispersion (chemical mapping) in order to investigate the influence of chemical ingredients and surface chemistry of the particle flocculation. The physical and chemical microstructural parameters will be correlated to the setting time and hydration heat signature using a moving window modeling approach. The setting and hardening process is considered to be the most critical time period for a concrete structure, during which chemical, physical and mechanical properties of the concrete undergo rapid changes. Remixing, recasting, or replacing cannot be implemented after setting. Thus having solid knowledge about the setting behavior of concrete is essential to guarantee the quality and performance of the material. Concrete setting is governed by paste setting that is caused by the distribution, movement, and connection of cement particles. An in-situ observation of the particle flocculation, agglomeration and percolation processes during the initial hydration period will provide fundamental understanding of paste setting behavior, so that the concrete construction process can be controlled. By combining Raman spectroscopy and confocal microscopy, this proposed work will build up a database on early-age hydration that will be useful to the concrete industry, specifically chemical admixture companies. This database will also be useful for hydration/microstructural development models. Educational plan focuses on training undergraduate and graduate students with better critical thinking and research skills. Outreach activities, such as INSPIRE and E-Expo, are also planned for diverse groups of K-12 students, including minority and female students.