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Coal Ash Characterization


The EERC has developed a flexible protocol for a comprehensive characterization of coal combustion byproducts (CCBs) to determine the appropriateness of a specific byproduct for utilization. This characterization scheme includes both scientific and empirical investigations of three major areas:

1. Physical characterization is an essential step in determining the expected behavior of CCBs for utilization. Information on compaction, self-hardening properties, flow properties, permeability, and behavior noted on mixing with cement or lime is important to predicting the suitability of these complex materials for utilization. Many of these properties can be determined by American Society for Testing and Materials (ASTM) methods. Results of physical characterization will be evaluated in conjunction with the chemical and mineralogical characterization results in order to identify the best technical use application for the selected materials.

2. Chemical characterization, the study of bulk chemical composition of CCBs, is also important in determining the appropriateness of a specific byproduct for many utilization applications. Major and trace elemental composition will be determined in all materials selected for this work. Bulk chemistry is reported as common oxides according to ASTM conventions. Trace element composition may be determined if warranted by environmental leaching procedures or if specific use applications may be impacted by the presence of trace constituents. The chemical characterization scheme for utilization and disposal also includes an evaluation of the leaching characteristics of the materials.

3. Mineralogical characterization for crystalline phases present is done by x-ray diffraction (XRD). Even in complex materials, the crystalline phases present are determined by their characteristic peaks in x-ray diffractograms. These peaks can be identified by comparing them to a database of minerals and other inorganic phases (the Powder Diffraction File). The great advantages of this method are that it is rapid and relatively inexpensive. Selected samples will also be analyzed using computer-controlled scanning electron microscopy (CCSEM). CCSEM is used in conjunction with XRD and SEM morphology for ash particle size and chemistry.