Longevity of borehole and shaft sealing materials: thermodynamic properties of cements and related phases applied to repository sealing

Technical Report · Wed Sep 01 00:00:00 EDT 1982

OSTI ID:6765526

Sarkar, A K; Barnes, M W; Roy, D M

Cements are being considered for sealing boreholes, shafts, and tunnels in nuclear waste repositories. The phases which will be stable in the long run are those which have the lowest free energies under repository conditions. In order to identify these phases, the relevant thermodynamic literature has been reviewed and evaluated, and some calculations of thermodynamic properties have been made for plausible repository conditions. Best values of heats, entropies, and free energies of formation are presented for calcium silicates, aluminates, and ferrites. Data for C-S-H gel are presented, considering the gel to have a composition of Ca/sub 3/Si/sub 2/O/sub 7/.3H/sub 2/O, and compared to the data for comparable crystalline phases. Equations and thermodynamic properties, including temperature dependence, are given for the hydration of cement components. Calculations for specific reactions show that hydration of tricalcium silicate should produce hillebrandite, 2CaO.SiO/sub 2/.1.17H/sub 2/O; the presence of excess silica should make higher-silica phases such as hillebrandite, tobermorite, or others more stable. The equilibrium between tobermorite, 5CaO.6SiO/sub 2/.5.5H/sub 2/O, and xonotlite, 6CaO.6SiO/sub 2/.H/sub 2/O, was calculated. Calculations of free energy of reaction of aqueous ions with tricalcium aluminate to form salts show that under normal atmospheric pressure and temperature Friedel's salt, the tricalcium aluminate monochloride hydrate, is stable both in typical brines and in a basalt groundwater. Similarly, in a brine from Los Medanos in the Delaware Basin of New Mexico, the tricalcium aluminate trisulfate-hydrate ettringite is stable with respect to tricalcium aluminate and to tricalcium aluminate monosulfate hydrate, but not with respect to hydrogarnet (tricalcium aluminate hexahydrate). 3 figures, 23 tables.

• Research Organization: Pennsylvania State Univ., University Park (USA). Materials Research Lab.
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 6765526
• Report Number(s): ONWI-201; ON: DE83000731
• Resource Relation: Other Information: Portions of document are illegible
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
36 MATERIALS SCIENCE
CEMENTS
THERMODYNAMIC PROPERTIES
RADIOACTIVE WASTE STORAGE
SEALING MATERIALS
ALUMINATES
BOREHOLES
BRINES
CALCIUM COMPOUNDS
CALCIUM SILICATES
CALCIUM SULFATES
EVALUATED DATA
FERRITES
GROUND WATER
HYDRATES
HYDRATION
MINERALS
PHASE STUDIES
RADIOACTIVE WASTE FACILITIES
STABILITY
TUNNELS
UNDERGROUND STORAGE
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
BUILDING MATERIALS
CAVITIES
DATA
FERRIMAGNETIC MATERIALS
HYDROGEN COMPOUNDS
INFORMATION
IRON COMPOUNDS
MAGNETIC MATERIALS
MANAGEMENT
MATERIALS
NUCLEAR FACILITIES
NUMERICAL DATA
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SILICATES
SILICON COMPOUNDS
SOLVATION
STORAGE
SULFATES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
UNDERGROUND FACILITIES
WASTE MANAGEMENT
WASTE STORAGE
WATER
052002* - Nuclear Fuels- Waste Disposal & Storage
360602 - Other Materials- Structure & Phase Studies