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 compared to the atomic-scale changes observed in pure (N,K)-ASH geopolymer gels.
