Utilization of fly ash from fluidized bed combustion of a Turkish lignite in production of blended cements

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2006

Öğrenci: MEHMET KÜRKÇÜ

Eş Danışman: MUSTAFA TOKYAY, NEVİN SELÇUK

Özet:

Fly ashes generated from fluidized bed combustion of low calorific value, high ash content Turkish lignites are characterized by high content of acidic oxides, such as SiO2, Al2O3 and Fe2O3, varying in the range 50-70%. However, there exists no study for the investigation of the possibility of using these ashes as concrete admixture. Therefore, in this study, characterization of fly ashes from fluidized bed combustion of a Turkish lignite and evaluation of these fly ashes as a substitute for Portland cement in production of pastes and mortars were carried out. The samples were subjected to chemical, physical, mineralogical and morphological analyses. Results of chemical and physical analyses of three fly ash samples show that they satisfy the requirements of EN 197-1, EN 450 and ASTM C 618, except for CaO and SO3, owing to high content of acidic oxides of these ashes contrary to majority of FBC fly ashes reported in the literature. In addition to characterization studies, water requirement, compressive strength, setting time and soundness tests were also performed for 10%, 20% and 30% fly ash-cement blends and the reference cement. Results of these tests reveal that the blends meet compressive strength, setting time and soundness requirements of ASTM C 595 without any pre-hydration treatment, and that fly ashes from fluidized bed combustion of Turkish lignites have significant potential for utilization as an admixture in manufacture of blended cements.