Bentonite slurry walls in modern construction
Bentonite slurry walls are used in construction, where the slurry wall is a trench filled with a thick colloidal mixture of Bentonite and water. A trench that would collapse due to the hydrolic pressure in the surrounding soil does not collapse as the slurry balances the hydraulic pressure. Forms for concrete, and rebar, can be assembled in a slurry filled trench, and then have concrete poured into the form. The liquid concrete is heavier than the bentonite slurry, and displaces it, and it can be re-used in a new trench elsewhere on the construction site.
In addition, because the colloid is relatively impervious to water, a slurry wall can prevent the seepage of groundwater, which is useful in preventing the further spread of ground-water that has been contaminated by toxic material like industrial waste.
History and natural occurrence
In 2005, U.S. was the top producer of bentonite with almost one-third world share followed by China and Greece, reports the British Geological Survey.
The absorbent clay was given the name bentonite by Wilbur C. Knight in 1898, after the Cretaceous Benton Shale near Rock River, Wyoming.[16] Other modern discoveries include montmorillonite discovered in 1847 in Montmorillon in the Vienne prefecture of France, in Poitou-Charentes, South of the Loire Valley.
Most high-grade natural sodium bentonite is produced from the western United States in an area between the Black Hills of South Dakota and the Bighorn Basin of Wyoming. Mixed sodium/calcium bentonite is mined in Greece, Australia, India, Russia, and the Ukraine. In the United States, calcium bentonite is mined primarily in Mississippi and Alabama. Other major locations producing calcium bentonite include Germany, Greece, Turkey, India, and China.
It should be noted that, in some countries like the UK and US, calcium bentonite is known as fuller’s earth, a term also used to refer to attapulgite, in terms of mineralogy, a distinct clay mineral but one exhibiting similar properties.