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

这项教师早期职业发展（Career）计划的拨款将用于开发新的内部固化剂，用于创造具有更高强度和耐久性的高性能混凝土。高性能混凝土容易出现龄期早期收缩，随后在体系内部形成裂缝，导致混凝土结构强度和寿命显著降低。为了解决这个问题，在混凝土混合物中加入充满水的内部固化剂。随着混凝土的固化，这些药剂释放了储存的水分，促进了固化反应，消除了早期的收缩和开裂。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（水基果冻状材料），不仅释放水以促进内部固化，而且在化学上增强固化反应并改善最终的混凝土微观结构。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和替换为具有更高性能的混凝土，并在混凝土的使用寿命期间降低经济和环境成本。因此，这项研究项目的结果将直接有利于美国经济以及普通民众的福祉和安全。该项目还将为工程专业学生提供克服基础设施材料性能障碍所需的多学科教育和培训，并提高社会对材料研究如何解决基础设施建设中重要挑战的认识。一种新型的水凝胶型内部固化剂的创造，可以同时增强固化反应和改善混凝土微观结构，只有在对分子水平结构-性能关系的基本理解的基础上，通过自下而上的合成设计才有可能。目前迫切需要确定用于高性能混凝土的水凝胶基内部固化剂的材料特性如何受到水凝胶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。为了解决这一关键需求，研究团队将定制合成模型高吸水聚合物-火山灰复合水凝胶，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-水泥混合物的和易性，以及由此产生的内部固化混凝土的微观结构和强度。研究活动将包括流变物理实验，以确定水凝胶-水泥混合物的局部流动剖面，以及早期混合物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.