CAREER: Water-based Gels containing Polymer and Cement-like Particles for Improved Curing of High-Performance Concrete

这项学院早期职业发展(Career)计划拨款将导致开发新的内部固化剂，用于创造提高强度和耐久性的高性能混凝土。高性能混凝土容易出现早期收缩和随后在系统内部形成裂缝，导致混凝土结构的强度和使用寿命显著降低。为了解决这个问题，在混凝土混合料中加入了充满水的内部固化剂。当混凝土养护时，这些试剂释放储存的水并推动养护反应，消除早期收缩和裂缝。该奖项支持对基于水凝胶的内部固化剂的化学和物理结构的基础研究，以开发新的复合水凝胶(水基类凝胶材料)，这种复合水凝胶不仅可以释放水分来促进内部养护，而且还可以在化学上增强固化反应，并改进由此产生的混凝土微观结构。这些新的内部固化剂将使混凝土具有更高的强度和耐腐蚀性，从而使美国老化的基础设施得以修复，并在混凝土的更长寿命内更换为具有更好性能并降低经济和环境成本的混凝土。因此，这一研究项目的结果将直接惠及美国经济以及普通民众的福祉和安全。该项目还将为工科学生提供所需的多学科教育和培训，以克服基础设施材料的性能障碍，并提高社会对材料研究如何应对基础设施建设中的重大挑战的认识。只有在对分子级结构-性能关系有基本了解的基础上，通过自下而上的合成设计，才能创造出一种新型的水凝胶内部固化剂，同时增强固化反应并细化混凝土微观结构。高性能混凝土中使用的水凝胶基内固化剂的材料性能如何受到水凝胶的分子结构以及水凝胶与混凝土和孔隙流体的相互作用的影响是迫切需要确定的。为了满足这一关键需求，研究小组将定制合成高吸水性聚合物-火山灰复合水凝胶模型，以确定复合水凝胶的物理和化学结构如何直接控制水凝胶的膨胀机制和机械性能、水凝胶-水泥混合物的工作性以及由此产生的内部养护混凝土的微观结构和强度。研究活动将包括流变实验，以确定水凝胶-水泥混合料的局部流动情况，以及早期混合料微观结构变化的先进成像。

This Faculty Early Career Development (CAREER) Program grant will lead to the development of new internal curing agents to be used for the creation of high-performance concrete that has increased strength and durability. High-performance concrete is prone to early-age shrinkage and the subsequent formation of cracks within the system, resulting in concrete structures with significantly reduced strength and lifetime. To combat this problem, water-filled internal curing agents are added to the concrete mixture. As the concrete cures, the agents release the stored water and fuel the curing reaction, eliminating the early-age shrinkage and cracking. This award supports fundamental research on the chemical and physical structure of hydrogel-based internal curing agents in order to develop new composite hydrogels (water-based jelly-like materials) that not only release water to promote internal curing but also chemically enhance the curing reaction and refine the resulting concrete microstructure. These new internal curing agents will result in concrete with increased strength and corrosion resistance, allowing for the aging infrastructure in the U.S. to be repaired and replaced with concrete that has greater performance and reduced economic and environmental costs over the increased lifetime of the concrete. Therefore, results from this research project will directly benefit the U.S. economy as well as the well-being and safety of the general population. This project will also provide engineering students with the multidisciplinary education and training required to overcome performance barriers in infrastructure materials as well as increase societal awareness of how materials research can address important challenges in infrastructure construction.The creation of a new class of hydrogel-based internal curing agents that simultaneously enhance the curing reaction and refine the concrete microstructure is only possible through bottom-up synthetic design informed by a fundamental understanding of molecular-level structure-property relationships. There is a critical need to identify how the material properties of hydrogel-based internal curing agents used in high-performance concrete are influenced by the molecular structure of the hydrogel and the interactions of the hydrogel with the concrete and pore fluid. To address this critical need, model superabsorbent polymer-pozzolan composite hydrogels will be custom synthesized by the research team to determine how the physical and chemical structure of the composite hydrogels directly controls the swelling mechanisms and mechanical properties of the hydrogels, the workability of hydrogel-cement mixtures, and the resulting microstructure and strength of internally cured concrete. Research activities will involve rheophysical experiments to determine local flow profiles of hydrogel-cement mixtures as well as advanced imaging of microstructural changes in early-age mixtures.