Collaborative Research: A Multi-Physics Approach to Advance Sustainable Engineering Materials

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Geopolymers have tremendous potential to be used as a sustainable material for structural engineering applications. Compared to portland cement concrete, geopolymers are more durable and less energy- and resource-intensive to manufacture due to their use of waste by-product materials. However, their widespread adoption is hindered due to a lack of understanding about geopolymer formation. Using a nondestructive microwave technique coupled with materials characterization methods, geopolymer reaction mechanisms can be studied and modeled, especially those involving water. The outcomes of the project will provide material design tools for geopolymers to become a staple material used to build the nation?s future sustainable structures. This research will also improve the prediction of strength, durability, and early-age properties of current structural materials such as portland cement concrete and advance other future materials with similar compositions. Further, the microwave-based assessment technique evolved from this project will enable in-situ evaluation of materials that undergo a hardening reaction after placement in the field thereby offering structural health monitoring and enhancing the construction quality control. This work will also include mentoring a diverse team of researchers and development of outreach activities that support the success of Native American, minority, female, and undergraduate students.This research will advance the fundamental understanding of geopolymer reaction mechanisms, which is critical for the advancement of viable geopolymer compositions for use as sustainable structural materials. Microwave techniques will be used to discern changes in material properties through dielectric measurements. Dielectric mixing models will be corroborated with multi-scale materials characterization techniques to quantify changes in water binding and corresponding phase composition transformations in geopolymers. This multi-physics approach will culminate in two new material models. The first model will link the phase formation mechanisms that occur during geopolymerization reaction with setting, rheological, and mechanical behavior. The second model will extend Powers Model for cement hydration to alkali-activated materials. Such a model will allow materials engineers to optimize geopolymer microstructures based on composition and curing inputs. These models can be extended for other materials with calcium-silicate chemistries and variable water binding. This work will also lay the groundwork for in-situ test methods suitable for assessment of geopolymer maturity, thereby offering structural health monitoring and improved quality control.