Designing High Performance Geopolymer Concrete Using Fly Ash and Slag

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dc.contributor.authorLi, Yanping
dc.date.accessioned2017-12-18T21:19:35Z
dc.date.available2017-12-18T21:19:35Z
dc.date.issued2015-08
dc.descriptionM.S. University of Hawaii at Manoa 2015.
dc.descriptionIncludes bibliographical references.
dc.description.abstractA fly ash-based geoploymer was studied as a potential alternative to traditional Portland cement since fly ash has significantly lower CO2 contribution than traditional cement production. The fly ash-based geopolymer was developed using fly ash, slag, and alkali solution, which when combined with aggregate produces a material that has high compressive strength, acceptable workability, and suitable setting time. The compressive strength and setting time of fly ash-based geopolymer paste/mortar were studied by varying the components of the alkali solution, slag replacement content, curing temperature, and liquid to binder ratio (L/B). The workability of the geopolymer paste/mortar was examined by introducing water and super plasticizer. The compressive strength development and cracking phenomenon of the geopolymer concrete were investigated by changing the L/B ratios and curing methods. The microstructural and mineralogical characteristics of geopolymer mortars were characterized using scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and Raman spectroscopy. Due to the complex reactions involved in geopolymer formation, hydroxide concentration and slag replacement percentage on setting time, 7-day and 28-day compressive strength. The results revealed that the compressive strength was dramatically enhanced by introducing slag into the fly ash-based geopolymer due to the formation of C-S-H and a large amount of geopolymer gel. In addition, the compressive strength was controlled by the [OH-] and [Si] concentrations of alkali solution. OH- accelerated the dissolution of glass, while silicate had a more complex role of maintaining the balance of species in solution. Elevated curing temperature resulted in higher compressive strength than room temperature. Higher compressive strength was obtained by using lower L/B ratio. The workability was controlled by L/B ratio and silicate concentration. The setting time was controlled by solution chemistry and slag content. The formation of C-S-H and geopolymer gel was confirmed using SEM/EDS and Raman spectroscopis analyses. The DOE results showed that: for setting time, [OH-], the interaction of [Si] and [OH-], and quadratic (second-order) effect of [Si] were considered significant; for 7-day compressive strength, only [Si], [GGBS/cem] and their interaction were considered significant, while [OH-] was considered not significant; for 28-day compressive strength, all factors appeared to be important.
dc.identifier.urihttp://hdl.handle.net/10125/51063
dc.language.isoeng
dc.publisher[Honolulu] : [University of Hawaii at Manoa], [August 2015]
dc.relationTheses for the degree of Master of Science (University of Hawaii at Manoa). Civil & Environmental Engineering
dc.subjectGeopolymer
dc.subjectFly ash
dc.subjectSlag
dc.subjectAlkali solution
dc.subjectCompressive strength
dc.subjectSetting time
dc.titleDesigning High Performance Geopolymer Concrete Using Fly Ash and Slag
dc.typeThesis
dc.type.dcmiText

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