Browsing by Subject "geopolymer"
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Item Effect of Water-Solids Ratio on the Compressive Strength, Degree of Reaction and Microstructural Characterization of Fly Ash-Waste Glass-Based Geopolymers(2017-04) Jansen, MatthewOn a global scale, the production of portland cement is responsible for approximately 5% of carbon emissions. In an effort to reduce carbon emissions, alternative binders are being implemented into the cement industry. Geopolymer technology combines aluminosilicate sources with an alkali solution to create a binder that has the potential to completely eliminate the need for portland cement in concrete. There has been limited research regarding the effect that the water-solids ratio (similar to water-cement ratio) has on geopolymer performance. For that reason, this research focused on the effect of the water-solids ratio on compressive strength, degree of reaction, and microstructure of fly ash – waste glass-based geopolymer mortars. Geopolymer mortars made of varying levels of fly ash and waste glass were produced. Three water-solids ratios were examined for each mixture, and compressive strength, degree of reaction, and microstructure characteristics were investigated in an effort to discover trends. Results showed that the water-solids ratio had an effect on compressive strength, but not a significant effect on degree of reaction. When comparing mixture compositions, mixtures containing fly ash seemed to be more sensitive to the water-solids ratio. Unreacted particles and different types of zeolites, depending on the mixture composition, were observed during microstructural analysis. Locations where particles seemed to have been “pulled-out” of the geopolymer paste were also observed in mixtures with higher water-solids ratios. However, more research is required to confirm these conclusions.Item Waste Glass as a Primary Precursor and Secondary Aluminosilicate Source in Geopolymer Mortars(2018-10) Haapala, KyrstynWidespread use of concrete as a construction material has led to concerns with the level of CO2 emissions from the production of portland cement. This has led to the development of alternative cements; geopolymers are one of these binders and the focus of this research. Geopolymers are formed through the combination of an aluminosilicate source and an alkaline activator. One of the largest contributions to CO2 emissions associated with geopolymers comes from the production of sodium silicate, which is commonly used as an activator. One of the primary goals of this research was to reduce or eliminate the need for sodium silicate in geopolymers by investigating the use of waste glass as a primary precursor or a secondary aluminosilicate source. Two types of geopolymers were produced where waste glass was used both as the main aluminosilicate source (Phase I) and as a supplement to fly ash (Phase II). Three activators with varying ratios of sodium silicate to sodium hydroxide (SS/NaOH) were considered and mixed with various glass sources to determine the effect of glass composition on performance. Fresh properties and compressive strength were measured, and SEM imaging was completed. Curing time, curing temperature, and calcium content were also investigated. Overall, including sodium silicate as an activator reduced the strength of glass-based geopolymers. A SS/NaOH of 1:1 (SiO2/Na2O = 0.95) was found to be optimal to activate the fly ash sources. Waste glass could not fully replace sodium silicate in activating fly ash and had limited success as a partial replacement while reducing the amount of sodium silicate in the activator.