Physical chemistry of Portland-cement hydrate, radioactive-waste hosts. Progress report, June 15, 1984-January 15, 1985
Phase relations in the system 3CaO.A1/sub 2/O/sub 3/-CaSO/sub 4/-CaI/sub 2/-H/sub 2/O in equilibrium with excess water were established by means of room temperature bottle hydration of various bulk chemistries in the system. Starting with end members ettringite (3CaO.A1/sub 2/O/sub 3/.3CaSO/sub 4/.32H/sub 2/O) and tetracalcium aluminate monosulfate-12-hydrate (3CaO.A1/sub 2/O/sub 3/.CaSO/sub 4/.12H/sub 2/O), iodine-substituted analogue phases were synthesized which contained increasingly greater percentages of iodine. The iodine-substituted ettringite was found to be unstable whereas the iodine-substituted monosulfate formed readily. SEM, wet chemistry, ir, and x-ray diffraction characterization of the latter phase suggest that its formula is 3CaO.A1/sub 2/O/sub 3/.Ca(IO/sub 3/)/sub 2/.12H/sub 2/O. Cement pellets containing this AFm iodine-substituted phase were subjected to a modified MCC-1 static leach test. Although the normalized iodine leach rate was relatively high when compared with AgI encapsulated in Portland Type III cement, this same leach rate was approximately equal to the rates that have been reported for Ba(IO/sub 3/)/sub 2/,Ca(IO/sub 3/)/sub 2/, and Hg(IO/sub 3/)/sub 2/ in Portland cement. The normalized iodine leach rate obtained also was found to be roughly comparable to that given for I-sodalite in cement. Diffusion is indicated as the primary leach mechanism, becoming dominant after the first three days of leaching. A study of phase relations of compositions in the vicinity of Stratling's compound (2CaO.A1/sub 2/O/sub 3/.SiO/sub 2/.8H/sub 2/O) has shown that the addition of finely divided silica or calcium aluminates to Portland cement enhance the immobilization of cesium in the cementitious-waste form. The leachability of cesium from such adjusted cements show a near linear relationship. If the calcium to silica ration is held constant, the cesium concentration of the leachate falls with increasing alumina content. Potential phases responsible for this behavior may be Stratling's compound and/or a zeolite phase.
- Research Organization:
- Pennsylvania State Univ., University Park (USA). Materials Research Lab.
- DOE Contract Number:
- FG02-84ER45145
- OSTI ID:
- 5985350
- Report Number(s):
- DOE/ER/45145-1; ON: DE85006791
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
ALUMINIUM OXIDES
PHASE DIAGRAMS
CALCIUM IODIDES
CALCIUM OXIDES
CALCIUM SULFATES
CESIUM
LEACHING
IODINE
PORTLAND CEMENT
PHYSICAL CHEMISTRY
EXPERIMENTAL DATA
HYDRATES
MATRIX MATERIALS
SILICA
WASTE FORMS
ALKALI METALS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
BUILDING MATERIALS
CALCIUM COMPOUNDS
CALCIUM HALIDES
CEMENTS
CHALCOGENIDES
CHEMISTRY
DATA
DIAGRAMS
DISSOLUTION
ELEMENTS
HALIDES
HALOGEN COMPOUNDS
HALOGENS
INFORMATION
IODIDES
IODINE COMPOUNDS
MATERIALS
METALS
MINERALS
NONMETALS
NUMERICAL DATA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
SEPARATION PROCESSES
SILICON COMPOUNDS
SILICON OXIDES
SULFATES
SULFUR COMPOUNDS
360602* - Other Materials- Structure & Phase Studies
052001 - Nuclear Fuels- Waste Processing