SusChEM: Nanostructural Stability of Alkali-Activated (N,K)-ASH Geopolymer Cements for Sustainable and Resilient Civil Infrastructure

本研究旨在通过推进替代水泥材料的材料科学来提高基础设施的可持续性，从而减少与波特兰水泥制造相关的生态影响。这项工作的结果涉及新型地质聚合物水泥的长期耐久性，应有助于确保下一代民用基础设施建筑材料的弹性和使用寿命性能。此外，这项研究旨在为新型废物和雨水基础设施建设材料的科学和工程奠定技术基础，这些材料利用了碱活化材料中可能形成的二级（沸石）结构的污染物去除潜力。波特兰水泥的生产约占全球二氧化碳排放量的8%。虽然PI（和其他人）的初步研究表明，基于粉煤灰和偏高岭土的碱活化地质聚合物水泥可以提供波特兰水泥的耐用低碳替代品（特别是用于水利基础设施应用），但对地质聚合物水泥中（N，K）-ASH凝胶的实际物理和化学降解机制知之甚少。了解和控制这些机制是确保地质聚合物基胶凝材料在民用基础设施应用中广泛使用之前的可持续性和长期耐久性的关键下一步。本研究的具体目标是调查（N，K）-ASH地质聚合物凝胶纳米结构在物理和化学环境压力下的时间依赖性稳定性。（N，K）-ASH凝胶的纳米结构稳定性的基础知识是必要的，以生产可持续的，耐用的地质聚合物为基础的替代品，以传统的波特兰水泥。该研究计划分为三个实验阶段。在第一阶段，合成（N，K）-灰地质聚合物凝胶的结构和性能将在纳米，微米和介观尺度上进行表征。在第二阶段，将结合魔角旋转核磁共振、傅里叶变换红外光谱和定量X射线衍射来研究（N，K）-ASH凝胶在（1）去离子水、（2）二氧化碳和（3）酸性介质存在下的原子级降解。在第三阶段，将研究偏高岭土基（N，K）-ASH凝胶的物理和化学降解，并将其与纯（N，K）-ASH地质聚合物凝胶中观察到的原子尺度变化进行比较。

This research aims to enhance infrastructure sustainability by advancing the materials science of alternative cementitious materials that reduce ecological impacts associated with Portland cement manufacture. The results from this work, which concerns the long-term durability of novel geopolymer cements, should aid in ensuring the resiliency and service-life performance of next-generation civil infrastructure construction materials. Furthermore, this research aims to lay the technical foundation for the science and engineering of novel waste- and stormwater infrastructure construction materials that leverage the pollutant removal potentials of secondary (zeolitic) structures that may form in alkali-activated materials. Manufacture of portland cement is responsible for approximately 8 percent of global carbon dioxide emissions. While preliminary research by the PI (and others) has shown that fly ash- and metakaolin-based alkali-activated geopolymer cements can provide a durable, low-carbon alternative to Portland cement (especially for water infrastructure applications), the actual physical and chemical degradation mechanisms of (N,K)-ASH gels in geopolymer cements are poorly understood. Understanding and controlling these mechanisms is a vital next step to ensure both the sustainability and long-term durability of geopolymer-based cementitious materials prior to their widespread use in civil infrastructure applications. The specific objective of this research is to investigate the time-dependent stability of (N,K)-ASH geopolymer gel nanostructures in the presence of both physical and chemical environmental stressors. Fundamental knowledge on the nanostructural stability of (N,K)-ASH gels is necessary to produce sustainable, durable geopolymer-based alternatives to conventional portland cement. The research program is organized into three experimental phases. In Phase I, the structure and properties of synthetic (N,K)-ASH geopolymer gels will be characterized at the nano-, micro-, and mesoscale. In Phase II, atomic-scale degradation of (N,K)-ASH gels in the presence of (1) deionized water, (2) carbon dioxide, and (3) acidic media will be investigated using a combination of magic angle spinning nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and quantitative x-ray diffraction. In Phase III, the physical and chemical degradation of metakaolin-based (N,K)-ASH gels will be investigated and comparedto the atomic-scale changes observed in pure (N,K)-ASH geopolymer gels.