Browsing by Author "Ozen, Sevgi"

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Effect of characteristics of natural zeolites on their geopolymerization
(ELSEVIERRADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS, 2021) Ozen, Sevgi; Uzal, Burak; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Uzal, Burak
The properties of clinoptilolite-based geopolymers are investigated with a focus on the parameters affecting the reactivity of clinoptilolite in a geopolymer binder. A complete characterization of raw materials was carried out as well as a determination of the mineralogical composition, microstructure and mechanical properties of geopolymers. The results of the investigation show that of the investigated materials, geopolymer made with clinoptilolite-bearing tuff from Bayburt has the highest compressive strength. The chemical and mineralogical characteristics of a raw material are important parameters that potentially control the geopolymeric reaction, whereas physical properties (particle size and BET specific surface area) are mainly influential at early stages of geopolymerization. Geopolymeric gel was found to be the main reaction product through characterization by XRD and SEM analysis. The geopolymer produced with the raw material from Bayburt had a narrow range of Si/Al ratios and possessed a geopolymer binder structure with an advanced nature. Lastly, in addition to clinoptilolite, feldspar has an additional effect on the geopolymeric reaction and enhances the process, especially at later ages.
Effect of mineralogical composition of clinoptilolite-bearing tuffs on their performance as a natural pozzolan in cementitious systems
(TECHNO-PRESSPO BOX 33, YUSEONG, DAEJEON 305-600, SOUTH KOREA, 2021) Ozen, Sevgi; Uzal, Burak; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Uzal, Burak
In this study, pozzolanic reactivity and strength activity of zeolitic tuffs containing similar amount of zeolitic phase (clinoptilolite) and different types and amounts of impurities were examined in order to understand the role of mineralogical composition in the efficiency of zeolitic natural pozzolans. Mineralogical and chemical compositions as well as the physical properties of the zeolitic tuffs were determined. Their pozzolanic reactivity were measured as depletion of calcium hydroxide in the pastes containing lime and zeolitic tuff, which is determined by thermogravimetric analysis. Furthermore, compressive strength of blended cement mortars prepared with 20% replacement of Portland cement by finely ground tuffs were determined at 7, 28 and 56 days of age. It was demonstrated that the type and amount of impurities in mineralogical composition of zeolitic tuffs are significantly effective on their early pozzolanic reactivity. Zeolite mineral content, however, is more determinative on long term reactivity. For a strength activity, mineralogical composition was clearly effective on the preparation of mortar samples, which depends on water requirement of zeolitic tuffs.