Graduate Thesis Or Dissertation
 

Reactivity Testing of Waterglass and the Investigation into an Alternative Binder Enhanced with Cellulose Nanocrystals

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/8p58pn50v

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  • Most of the concrete in the world is produced using hydraulic cement (ordinary portland cement, OPC) and siliceous or alumino-siliceous supplementary cementitious materials (SCM). Due to the shift in focus toward environmental sustainability within the construction industry, alkali-activated cementitious systems (AAC) have gained significant attention to reduce the carbon footprint created by OPC clinker production. The use of AAC commercially is happening more frequently; however, it is limited by material availability. Increasing the number of available clinker-free options can help make their uses more feasible in more cases. This thesis explores the reactivity of waterglass and a new silica-based AAC binder. The chemical reactivity of waterglass, a type of sodium silicate, is investigated initially. Measuring the reactivity of waterglass requires procedural changes to the current reactivity tests. The interpretation of the reactivity test data also requires updated theoretical counterparts for comparing the test outputs to establish the degree of reactivity. A developed approach demonstrates how the quantified reactivity is used in thermodynamic calculations to predict the reaction products and paste properties. A new silica-based alternative binder using waterglass, calcium hydroxide, limestone, and potassium hydroxide solution is developed based on the thermodynamic models. The initial hurdles are high porosity, low workability, and low flexural strength. Various mixture characteristics are explored, along with the additions of silica fume and cellulose nanocrystals (CNCs). Silica fume is found to help increase strength and reduce porosity. CNCs show multi-faceted functionality, working as a water-reducer and a retarder to improve mechanical properties. This study of silica-based AAC results in a binder with a maximum flexural strength of 6.9 MPa, a 353% improvement from the initial results. Porosity is reduced by 22%, and the required w/s is reduced by 25%.
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  • Pending Publication
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  • 2022-10-06 to 2023-05-07

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