EAGER: Computed Tomography of Early Age Structure of Hydrated Portland Cement

这一早期概念探索性研究奖助金(AGER)项目推进了X射线计算机断层扫描(CT)技术的应用，以前所未有的方式观察水泥微观结构：未受干扰的湿样品随时间变化的三维图像。虽然CT正在成为一个强大的工具，可供越来越多的研究人员使用，但文献仍然很少。概念验证实验证明了这些新工具的力量，为水泥水化和微观结构发展提供了深刻的新见解。该项目的主要目标是开发用于水化硅酸盐水泥时间研究的实验方法。此类实验需要高分辨率、高精度的样品架以确保随时间的空间配准，需要特殊的密封样品架以防止蒸发，需要特殊的样品制备技术以确保样品代表散装水泥，以及成像协议以帮助进行相分割。这项拟议的研究将使用基于大学的纳米级X射线计算机断层扫描(由NSF大型设备拨款资助)和阿贡国家实验室同步辐射X射线计算机断层扫描。同步加速器CT分辨率高，但不适合学生长期学习。大学的CT为学生提供了长期学习的优越途径，但存在X射线通量较低的问题。这一急切的项目针对的是几乎没有开展过的工作，在实验方法方面几乎没有先例，但在理解水化硅酸盐水泥等多孔固体的复杂微观结构方面存在巨大的潜力。微观结构和材料建模的研究对帮助我们了解水泥和混凝土的性能、耐久性、生命周期性能和可持续性具有广泛的影响。毫无疑问，提高对材料的理解有可能改进建筑材料，延长已建成基础设施的使用寿命。本项目将获得的高分辨率三维图像为控制混凝土材料特性的孔隙网络和相的分布提供了重要的洞察。这些知识将导致新的产品和工艺，将改善未来的混凝土材料。

This EArly-concept Grant for Exploratory Research (EAGER) project advances the use of X-ray computed tomography (CT) to view cement microstructure like never before: three-dimensional images of undisturbed wet samples as a function of time. While CT is emerging as a powerful tool that is available to more and more researchers, the literature remains sparse. Proof of concept experiments have demonstrated the power of these new tools to provide profound new insights into cement hydration and microstructure development. The primary objectives of this project are the development of experimental methods for time studies of hydrating Portland cement. Such experiments require high resolution, high precision sample holders to assure spatial registration over time, special sealed sample holders that prevent evaporation, and special sample preparation techniques to assure that samples are representative of bulk cement, and imaging protocols to assist in segmentation of phases. The proposed study will use university-based nano-scale X-ray computed tomography (funded by an NSF large equipment grant) and Argonne National Lab synchrotron x-ray computed tomography. The synchrotron CT offers high resolution, but is not ideal for long term studies by students. The university CT offers superior access for students for long term studies, but suffers from being lower x-ray flux. This EAGER project aims where little work has been conducted, little precedent has been developed for experimental methods, but great potential exist to advance the science of understanding the complex microstructure of porous solids like hydrated portland cement.Study of microstructure and material modeling have broad impacts in helping us understand cement and concrete properties, durability, life cycle performance, and sustainability. There is no question that improved understanding of materials has potential to improve building materials and extend the service life of the built infrastructure. The high resolution 3-dimensional images that will be acquired in this project provide important insight into the pore network and distribution of phases that control material properties of concrete. Such knowledge will lead to new products and processes that will improve concrete materials in the future.