Morphology and Selected Properties of Fly Ash


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Title: Morphology and Selected Properties of Fly Ash

Author(s): P. K. Rohatgi, P. Huang, R. Guo, B. N. Keshavaram, and D. Golden

Publication: Special Publication

Volume: 153


Appears on pages(s): 459-478

Keywords: aluminum; composite materials; fly ash; morphology; placing; thickness; walls; Materials Research

Date: 6/1/1995

A new variety of applications are being found for fly ash. It is increasingly important to determine the structural properties of fly ash particles, especially for increasing use in composites, such as polymer matrix and cast metal matrix composites. In this paper, selected properties of precipitator fly ash and cenosphere fly ash were directly measured; other properties were indirectly estimated from the experimental measurements on the properties of composites containing fly ash. The properties studied included sphericity of fly ash particles, wall thickness, the ratio of wall thickness to diameter, and modulus. The data generated on properties of fly ash have been compared with other filler or reinforcement materials, such as glass microspheres, Al 2O 3 , SiO 2, and SiC particles. The results show that the deviation of cenospheres from sphericity is virtually independent of diameter. The ratio of wall thickness to diameter of cenospheres is about 0.1 and tends to decrease with increasing particle diameter. The calculated values of effective modulus of fly ash from the property measurements on metal matrix-fly ash composites are in the range of 140 to 310 GPa, which are of the same order of magnitude as of general ceramics and glasses. The morphology of precipitator and cenosphere fly ash particles studied using scanning electron microscope is discussed. The implications of the morphology and properties of fly ash on its utilization, especially in micro and macro composites, including cements, are also discussed.