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

Oklahoma State University, Stillwater OK

Investigators

Abstract

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.