Submicroscopic Structure and Characteristics of Intermediate-Calcium Fly Ashes

Abstract

The surface and near surface characteristics of alkaline fly ash particles were studied to evaluate the heterogeneous chemistry and structure of ash in order to provide data and understanding of the dissolution behavior of elemental constituents. Fly ash was subjected to a range of chemical weathering intensities in laboratory column experiments. Weathered ash from columns were then analyzed for surface morphology and chemical compositional change. Determinations included chemical characterization by instrumental neutron activation analyses, surface analysis by SEM-EDXA of whole and fractured particles, surface glass analysis by selective dissolution, and mineralogy by powder x-ray diffraction. These data were used to develop a physical model of fly ash particles that describes the heterogeneous distribution of elements on or in a reactive glass hull and in matrix glass and mullite. The model is discussed in terms of elemental partitioning and its application to the mechanistic approach advocated for prediction of leachate composition.