Title: Synthetic Glass Models for Investigating Fly Ash Reactivity

Author(s): W. Bumrongjaroen, S. Swatekititham, R.A. Livingston, and J. Schweitzer

Publication: Symposium Paper

Volume: 242

Issue:

Appears on pages(s): 227-242

Keywords: calcium aluminum silicate; fly ash; leaching; nuclear resonance reaction analysis; Raman spectroscopy; reactivity; synthetic glass

DOI: 10.14359/18717

Date: 4/1/2007

Abstract:
The reactive particles in fly ash are glassy with the major constituents: SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O, and K2O. From glass science, it is known that the reactivity would vary with these constituents. Therefore, it may be possible to develop a predictive model of reactivity based on chemical composition. However, it is difficult to study this in real fly ashes because the composition varies from one particle to another. It is not practical to separate the individual particles to isolate specific glass compositions. An alternative approach is to prepare synthetic glass samples with appropriate compositions. Thus calcium aluminum silicate glasses with specified CaO/Na2O+K2O ratios have been prepared as model systems. The compositions were selected to span the ranges measured in representative fly ashes using automated single particle elemental analysis. After characterization the silicate speciation of the glasses using Raman spectroscopy, the reactivity of the synthetic fly ashes was measured using a , inelastic neutron scattering and nuclear resonance reaction analysis. The results showed agreement with glass durability theory and demonstrated the advantages of using a synthetic glass model for fly ashes.