Identifying Glass Compositions in Fly Ash

Abstract

In this study, four Class F fly ashes were studied with a scanning electron microscope; the glassy phases were identified and their compositions quantified using point compositional analysis with k-means clustering and multispectral image analysis. The results showed that while the bulk oxide contents of the fly ashes were different, the four fly ashes had somewhat similar glassy phase compositions. Aluminosilicate (AS) glasses, calcium aluminosilicate (CAS) glasses, a mixed glass, and, in one case, a high iron glass were identified in the fly ashes. Quartz and iron crystalline phases were identified in each fly ash as well. The compositions of the three main glasses identified, AS, CAS, and mixed glass, were relatively similar in each ash. The amounts of each glass were varied by fly ash, with the highest calcium fly ash containing the most of calcium-containing glass. Some of the glasses were identified as intermixed in individual particles, particularly the calcium-containing glasses. Finally, the smallest particles in the fly ashes, with the most surface area available to react in alkaline solution, such as when mixed with Portland cement or in alkali-activated fly ash, were not different in composition than the large particles, with each of the glasses represented. The method used in the study may be applied to a fly ash of interest for use as a cementing material in order to understand its potential for reactivity.

Influence of Activators on Mechanical Properties of Modified Fly Ash Based Geopolymer Mortars

“…The micrographs on a 10-µ m scale clearly revealed particles' spherical shape for all fly ashes (Figure 3). EDS analysis confirmed that, in RFA and CFA, those particles were mostly built with silica and aluminum compounds typical for glassy aluminosilicates [56]. In BFA, particles were characterized by phosphate, calcium, and potassium compounds present in archerite, which is shown in the BFA structure by XRD.…”

Supplementary cementitious materials: New sources, characterization, and performance insights

“…Another avenue of research that is relevant for fly ashes and slag is the investigation of the reactivity of glasses present in these materials. Fly ashes contain a variety of glassy phases, mostly modified aluminosilicates [58]. Both calcium and aluminum are important network modifiers in glasses that affect reactivity [59].…”

Microstructure and Composition of Red Mud-Fly Ash-Based Geopolymers Incorporating Carbide Slag

“…X-Ray Diffraction, Scanning Electron Microscope, and Back Scattered Electron-Energy Dispersive X-Ray Spectroscopy Test of Geopolymers XRD SEM and BSE-EDS were used to test the factors including microstructure, mineral composition, and gel composition which affects the microscopic characteristics of fly ash-based geopolymers. Followed the test method mentioned in the literature (Aughenbaugh et al, 2016), each set of proportions in Table 4 was made into the 20 mm × 20 mm × 80 mm samples, and cured under the same curing conditions. The XRD test samples were taken from the non-carbonized zone in paste sample corresponding to D2.…”