Using In Situ Chemical and Structure Mapping of Calcium Sulfoaluminate Cement to Control Hydration

世界上使用最广泛的建筑材料是混凝土，因为它的耐久性、经济性和灵活的形式。由于混凝土无处不在，它对资源产生了相当大的需求。这意味着，即使混凝土的耐久性和可持续性稍有改善，也会带来巨大的社会效益和经济效益。需要性能更好的新型水泥，同时也需要减少生产资源。硫铝酸钙水泥就是一个很好的例子。与传统水泥相比，这些水泥生产所需的二氧化碳和能源减少了50%。这些水泥能够在三个小时内获得与传统水泥一个月获得的强度相当的强度。此外，这些材料在干燥时表现出较少的裂纹。然而，还需要了解并最终控制硫铝酸钙水泥的水化速度。本项目旨在通过使用3D原位结构和化学成像技术来表征纳米和微米尺度的水化反应的变化，从而了解这组水泥。还可以考察添加剂对这些水化反应改性的影响，并对其进行相应的改性。这些发现将用于以更低的成本和能源消耗生产性能更好的混凝土。此外，还将通过扩展现有的以基础工程为导向的课程，为在线和课堂教学创建新的教案，提高未被充分代表的小学生对STEM领域的认识水平。研究将使用多个长度尺度的3D原位结构和化学成像技术，并结合微观结构建模来表征、量化和了解前12小时硫铝酸钙水泥反应的结构、化学和性能。这些水泥可以在几个小时内获得使用强度，并有可能将混凝土的碳足迹减少50%。这项工作旨在利用纳米和微米级的3D原位成像技术，了解水泥颗粒溶解和随后形成早期水化产物过程中发生的结构和化学变化。还将使用机械测试、等温量热法和X射线衍射法来评估整体变化。接下来，这些相同的实验方法将被用来研究添加剂如何改变水合物的速率、结构和化学。最后，将努力了解这些反应发生的机制，并与国家科学和技术研究所合作开发能够指导设计和预测早期混凝土性能的计算模型。这项工作将提高混凝土的经济性、可持续性和力学性能。

The most widely used construction material in the world is concrete, due to its durability, economy, and flexible form. Because concrete is so ubiquitous, it creates a sizable demand on resources. This means that even modest improvements in the durability and sustainability of concrete would lead to great societal and economic benefit. New cements are needed with improved performance that also require reduced resources to manufacture. Calcium sulfoaluminate cements are a good example of this. These cements have a 50 percent reduction in the carbon dioxide and energy required for their production when compared to traditional cement. These cements are capable of gaining comparable strengths in only three hours that traditional cements gain in a month. Furthermore, these materials show less cracking from drying. However, work is needed to understand and ultimately control the rate of hydration of calcium sulfoaluminate cements. This project aims to understand this group of cements by characterizing changes in the hydration reactions at nano and micro length scales using 3D in-situ structure and chemistry imaging techniques. The effects of additives on these hydration reactions modifying can also be examined and modified accordingly. These findings will be used to produce concretes with improved properties at lower costs and energy consumption. Also, the awareness level of STEM fields will be raised with underrepresented elementary students through the extension of an existing elementary engineering-oriented curriculum with the creation of new lesson plans for both online and in class delivery.The research will use 3D in-situ structure and chemistry imaging techniques at multiple length scales in combination with microstructural modeling to characterize, quantify, and understand the structure, chemistry, and properties of calcium sulfoaluminate cement reactions over the first 12 hours. These cements can gain service strengths in only a few hours and have the potential to reduce the carbon footprint of concrete by 50 percent. This work aims to understand changes in the structure and chemistry that occur in the dissolution of cement particles and the subsequent formation of early age hydration products by using 3D in-situ imaging techniques at the nanometer and micron scale. Bulk changes will also be evaluated by using mechanical testing, isothermal calorimetry, and X-ray diffraction. Next, these same experimental methods will be used to study how additives change the rate, structure, and chemistry of the hydrates. Finally, efforts will be made to understand the mechanisms by which these reactions occur and collaborate with the National Institute of Science and Technology to develop computational models that are able to guide the design and predict performance of early concrete properties. This work will improve economy, sustainability, and mechanical properties of concrete.