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

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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.