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The first set of samples, from a Class F ash settling pond in Kentucky disposed for up to 20 years, showed little mineralogical alteration, as expected. Four sets of borehole samples of disposed or utilized CCBs more » were retrieved and analyzed by RQXRD according to the protocols developed under the first objective. The RQXRD technique was initially tested using (1) mixtures of National Institute of Standards and Technology (NIST) crystalline standards, and (2) mixtures of synthetic reagents simulating various CCBs, to determine accuracy and precision of the method, and to determine the most favorable protocols to follow in order to efficiently quantify multi-phase mixtures. This study addressed these areas with two objectives, producing (1) a set of protocols for fully quantitative phase analysis using the Rietveld Quantitative X-ray Diffraction (RQXRD) method and (2) greater understanding of the hydrologic and geochemical nature of the long-term behavior of disposed and utilized CCBs.

Second, our understanding of the long-term behavior of various CCBs in contact with the natural environment was based on a relatively limited set of study materials. Rather, only semi-quantitative methods were available, with large associated errors.

First, no method had been successfully applied to achieve full quantitative analysis of the partitioning of chemical constituents into reactive or passive crystalline or noncrystalline compounds. Prior to the initiation of this study, understanding of the long-term behavior of environmentally-exposed Coal Combustion By-Products (CCBs) was lacking in (among others) two primary areas addressed in this work.

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