Swelling bentonite

Kohimeier, M., Kaiser, R., Kolditz, O., Zielke, W. 2002. Finite element simulation of consolidation and bentonite swelling in the framework of unsaturated porous media. In Hasanzadeh, S. M. et al. (eds.). Developments in Water Science, 47, Vol. I, pp. 57-64, Proc. XlV Int. Conf. on Computational Methods in Water Resources, June 23-28. 2002, Delft. 

In the near-field of a HLW repository, the coupled thermo -hydro -mechanical and chemical (T-H-M-C) processes will occur, involving the interactive processes among radioactive decay heat from the vitrified waste, infiltration of groundwater into bentonite, swelling pressure of bentonite due... 

Montmorillonite clays absorb water readily, swell greatly and confer highly plastic properties to a soil. Thus soil stress (Section 14.8) occurs most frequently in these soils and less commonly in predominantly kaolinitic types. Similarly, a soil high in bentonite will show more aggressive corrosion than a soil with a comparable percentage of kaolinite. A chalky soil usually shows low corrosion rates. Clay mineralogy and the relation of clays to corrosion deserves attention from corrosion engineers. Many important relationships are not fully understood and there is need for extensive research in this area. 

Bentonite is an impure clay that is formed by weathering of volcanic tuffs. It contains a high content of montmorillonite. Bentonites exhibit properties such as ability to swell, ion exchange, and thixotropy. Properties can be modified by ion exchange, for example, exchange of earth alkali metals to alkali metals. The specific surface can be modified with acid treatment. Organophilic properties can be increased by treatment with quaternary ammonia compounds. 

A water-expandable material based on bentonite clay and polyacrylamide is added to the circulating drilling solution [118]. The material expands in water to 30 to 40 times its initial volume. The swelling takes place within 2 to 3 hours. During the circulation of the drilling solution, the material enters the cracks and... 

Bentonite is the name for a hydrous aluminum silicate comprised principally of the clay mineral montmorillonite, notable for its ability to swell in water and to form a very low-permeability seal." It is available as powder, granule (chip), or pellets. Powder and granule sizes are produced by processing after mining. Bentonite powder... 

If bentonite pellets or chips are to be used instead of grout, the bentonite pellets can be placed in shallow wells (within 15.0 m of ground surface) by pouring them through the annular space from above in much the same manner as the filter pack is placed. If this installation procedure is chosen, sufficient potable water must be added in conjunction with the bentonite to hydrate the individual pieces. Hydration causes the pieces to swell and form a highly impermeable seal. 

The water used for a green sand system should be clean and it should be consistent. It should have a pH that is neutral to alkaline, not acidic, because acids prevent bentonite from swelling. In... 

The most significant class of inorganic supports, which is used for the direct ion exchange of positively charged transition-metal complexes, are smectite clays. Pin-navaia has introduced the use of these swelling, layered silicate clays for catalysis. Other clays include montmorillonite, bentonite, and laponite. As shown by Pinna-vaia, cationic transition-metal complexes can be readily exchanged (intercalated) into the solvated interlayers of these silicates (Eq. (1)) [117] ... 

Bentonites may generally be divided into two classes a) Those capable of absorbing large amts of water and which swell tremendously in the process. They also have the property of remaining in suspensions in thin water disDersions and b) Those that absorb no more water than ordinary plastic clays or Fuller s earth and do not swell appreciably. They settle rapidly in thin water dispersions... 

---