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Assessment of pozzolanic reactivity of class-F fly ashes through mineralogical & microstructural characterization
The effectiveness of low lime fly ash used in cement is determined to a large extent by three parameters viz. fineness, carbon content (Loss on Ignition) and the glassy phase content of the fly ash. In this work, typical Indian class-F fly ashes have been characterized for their physico-chemical and mineralogical properties. While the particle size distribution vary widely among the samples, the chemical and mineralogical characteristics vary with in a narrow range. The reactive silica content of the fly ash was determined following chemical treatment as per EN-196-2 method. The microscopic examination of the residue left after the chemical treatment reveals that this treatment attacks preferentially the glassy portion of the spherical particles of the fly ash. This observation was supported by the XRD analysis carried out on the fly ash before and after the chemical treatment. The XRD of the residue shows total disappearance of the amorphous hump and enhancement of crystalline quartz and mullite peaks. The SEM examination of classified fly ash fractions reveals that these glassy, spherical particles are predominantly present in the -45 micrometer fractions. This is further confirmed by higher reactive silica content obtained in this fraction. Also, the mortars containing -45 micrometer fraction of the fly ash show superior flow property as compared to the one with +45 micrometer fraction, due to the 'ball bearing effect' of the small spherical particles.
Assessment of pozzolanic reactivity of class-F fly ashes through mineralogical & microstructural characterization
The effectiveness of low lime fly ash used in cement is determined to a large extent by three parameters viz. fineness, carbon content (Loss on Ignition) and the glassy phase content of the fly ash. In this work, typical Indian class-F fly ashes have been characterized for their physico-chemical and mineralogical properties. While the particle size distribution vary widely among the samples, the chemical and mineralogical characteristics vary with in a narrow range. The reactive silica content of the fly ash was determined following chemical treatment as per EN-196-2 method. The microscopic examination of the residue left after the chemical treatment reveals that this treatment attacks preferentially the glassy portion of the spherical particles of the fly ash. This observation was supported by the XRD analysis carried out on the fly ash before and after the chemical treatment. The XRD of the residue shows total disappearance of the amorphous hump and enhancement of crystalline quartz and mullite peaks. The SEM examination of classified fly ash fractions reveals that these glassy, spherical particles are predominantly present in the -45 micrometer fractions. This is further confirmed by higher reactive silica content obtained in this fraction. Also, the mortars containing -45 micrometer fraction of the fly ash show superior flow property as compared to the one with +45 micrometer fraction, due to the 'ball bearing effect' of the small spherical particles.
Assessment of pozzolanic reactivity of class-F fly ashes through mineralogical & microstructural characterization
Bewertung der puzzolanischen Reaktivität von Flugaschen der Klasse F durch mineralogische und mikrostrukturelle Charakterisierung
Venkateswaran, D. (author) / D'Mello, J.J. (author) / Cursetji, R.M. (author)
2003
11 Seiten, 13 Bilder, 3 Tabellen, 10 Quellen
Conference paper
Storage medium
English
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