Title:
Microanalytical and Computational Analysis
of Class F Fly Ash
Author(s):
P. Jason Williams, Joseph J. Biernacki, Claudia J. Rawn, Larry Walker, and Jianming Bai
Publication:
Materials Journal
Volume:
102
Issue:
5
Appears on pages(s):
330-337
Keywords:
fly ash; scanning electron microscopy; x-ray diffraction
DOI:
10.14359/14712
Date:
9/1/2005
Abstract:
A Class F fly ash has been analyzed using synchrotron x-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) to determine the composition, phase distribution, particle size, and particle morphology. XRD showed the existence of mullite, quartz , Fe2O3 (hematite or maghemite), and CaSO4 (anhydrite), with the possibility of calcium hydroxide (CH), which was also confirmed using TGA. SEM and x-ray microanalysis indicate four particle types: 1) a mixed aluminosilicate (A-S) phase with variable amounts of calcium, iron, and magnesium; 2) quartz or glassy silica; 3) FeO, Fe2O3, or an MgO-FeO phase; and 4) Ca(OH)2 mixed with CaSO4. A combination of image analysis and XRD was used to identify and quantify the phase fraction of the major components in the system, including aluminosilicate glass and silica. These were used to construct segmented microstructures suitable for use in multi-scale microstructural simulations. Microanalysis also suggests that the A-S glassy portion of the ash may actually be two separately identifiable glasses or at least bounded by the compositions AS3 and A2S3.