X-ray Diffraction of Slag-based Sodium Salt Waste Forms.

摘要

The attached report documents sample preparation and x-ray diffraction results for a series of cement and blended cement matrices prepared with either water or a 4.4 M Na salt solution. The objective of the study was to provide initial phase characterization for the Cementitious Barriers Partnership referencecase cementitious salt waste form. This information can be used to: (1) generate a base line for the evolution of the waste form as a function of time and conditions, (2) potentially to design new binders based on mineralogy of the binder, (3) understand and predict anion and cation leaching behavior of contaminants of concern, and (4) predict performance of the waste forms for which phase solubility and thermodynamic data are available. Both water and a 4.4 M sodium salt solution were used to hydrate the cementitious reagents. One of the mixes containing the sodium salt solution and blended binder was approximated by the Cementitious Barriers reference case salt waste form. The other mixes contained combinations of the reference case binder ingredients. Mixes prepared with water were compared to literature data of typical blended cement matrices. The intent was to use this characterization data as a starting point for more detailed phase characterization using various techniques including neutron diffraction techniques in addition to quasi-elastic neutron scattering techniques for characterization of water at the ORNL Spallation Neutron Source, Oak Ridge, TN and other methods such as, thermogravimetric techniques, electron diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The initial characterization is complete. Due to extensive substitutions of cations and anions in the layered double hydroxide phases and the very fine intermixing of poorly crystalline hydrated phases in the reference case blend (10 : 45 : 45 cement : slag : fly ash), electron diffraction and transmission electron spectroscopy are recommended as the next step for characterization.