Some Physical, Chemical and Mineralogical Properties of Some Canadian Fly Ashes
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SOME PHYSICAL, CHEMICAL AND MINERALOGICAL PROPERTIES OF SOME CANADIAN FLY ASHES R.C. JOSHI and B.K. MARSH Department of Civil Engineering, University of Calgary, Calgary, Alberta, Canada Received 20 October, 1986; refereed ABSTRACT This paper gives physical and chemical properties of some Canadian fly ashes. Specific surface area, magnetic fraction, water soluble fraction and fraction finer than 45 pm were determined as part of the physical tests. Thermo-gravimetric analyses (TGA) in oxygen and nitrogen were conducted on raw ash samples. The change of pH with time in suspensions of the different ashes in water was also determined. Pozzolanic activity of the ashes with lime for all the ashes was evaluated to measure ash reactivity. The ash activity seems to be related to fineness of the ash measured by the Blaine air permeability method, but not to the fineness measured by nitrogen sorption. Generally the greater the specific surface area, the higher the reactivity of the ash. The correlation was, however, not strong and no other physical or chemical parameter measured in this investigation seems to be related to pozzolanic activity. The results of pH and TGA tests indicated that the ashes differ in many respects from each other. The TGA data suggest that loss-on-ignition in many of the ashes is not entirely due to the presence of unburned carbon. Specific surface area determined by various methods seems to provide different values. No characterization parameter was found that was uniquely related to coal type. INTRODUCTION Characteristics of any fly ash depend, amongst other factors, upon the coal type from which it is produced. The particular coal type used in power generation depends, in turn, to a large extent upon the geographical location of the plant. Across Canada there are many power plants using coal from many different sources. This paper compares physical, chemical and mineralogical properties of fourteen different ashes from Eastern, Central and Western Canada. The purposes of the investigation were to determine: 1. the various physical and chemical properties of fly ashes produced in different parts of the country, 2. the amount of ash within fractions of low specific gravity, particularly the ash fraction lighter than water, 3. the magnetic fraction within the ashes, 4. the nature of the loss-on-ignition of the various fly ashes by thermogravimetric analyses, and 5. correlations, if any, between the physical and chemical properties and the pozzolanic activity of the ashes.
Mat. Res. Soc. Symp. Proc. Vol. 86.
1987 Materials Research Society
114
Table I. Fly Ash No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Fly Ash Types and Sources Coal Type
Sources
Sub-Bituminous Sub-Bituminous Sub-Bituminous Sub-Bituminous Lignite Sub-Bituminous Lignite Lignite Bituminous Bituminous Bituminous Bituminous Bituminous (?) Sub-Bituminous
Alberta Alberta Alberta Alberta Saskatchewan Saskatchewan Saskatchewan Saskatchewan Ontario Ontario New Brunswick New Brunswick Nova Scotia Nova Scotia
MATERIALS AND EXPERIMENTAL METHOD
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