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Tuesday, 16 August 2011
Download free ACI Code Free Download (ACI-318-02)
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Monday, 15 August 2011
Bentonite History and Natural Occurrence ( wikipedia)
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. 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 primarily mined 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 which is also used to refer to attapulgite, a mineralogically distinct clay mineral but exhibiting similar properties
Contents and Tyeps Of Bentonite, Engineering Meterial Of Building Construction
Contents
2 Calcium bentonite
1: Sodium bentonite
Sodium expands when wet, absorbing as much as several times its dry mass in water. Because of its excellent colloidal properties (see Odom ref below), it is often used in drilling mud for oil and gas wells and for geotechnical and environmental investigations.
The property of swelling also makes sodium bentonite useful as a sealant, especially for the sealing of subsurface disposal systems for spent nuclear fuel] and for quarantining metal pollutants of groundwater. Similar uses include making slurry walls, waterproofing of below-grade walls, and forming other impermeable barriers, e.g., to seal off the annulus of a water well, to plug old wells, or to line the base of landfills to prevent migration of leachate.
Sodium bentonite can also be "sandwiched" between synthetic materials to create geo-synthetic clay liners (GCL) for the aforementioned purposes. This technique allows for more convenient transport and installation, and it greatly reduces the volume of sodium bentonite required.
Various surface modifications to sodium bentonite improve some rheological or sealing performance in geo environmental applications, for example, the addition of polymers.
Properties
Extracted Bentonite is distinctly solid, even with a moisture content of approximately 30%.
Bentonite is used as a bonding material in the preparation of molding sand for the production of iron, steel and non-ferrous casting.
Used as a binding agent in the production of iron ore pellets. Through this process, iron ore fines are converted into spherical pellets, suitable as feed material in blast furnaces for pig iron production, or in the production of direct reduction iron (DRI).
Acts as a good lubricating agent.
Excellent absorption and adsorption properties make it an ideal option for water purification.Calcium bentonite is a useful adsorbent of ions in solution. as well as fats and oils, being a main active ingredient of fuller's earth, probably one of the earliest industrial cleaning agents. Calcium bentonite may be converted to sodium bentonite (termed sodium beneficiation or sodium activation) to exhibit many of sodium bentonite's properties by a process known as "ion exchange" (patented in 1935 by Germans U Hofmann and K Endell). Commonly this means adding 5–10% of a soluble sodium salt such as sodium carbonate to wet bentonite, mixing well, and allowing time for the ion exchange to take place and water to remove the exchanged calcium. Some properties, such as viscosity and fluid loss of suspensions, of sodium beneficiated calcium bentonite (or sodium activated bentonite) may not be fully equivalent to natural sodium bentonite. For example, residual calcium carbonates (formed if exchanged cations are insufficiently removed) may result in inferior performance of the bentonite in geosynthetic liners.
Also known as potash bentonite or K-bentonite, potassium bentonite is a potassium-rich illitic clay formed from alteration of volcanic ash.
Aluminum- 18.1%
Iron- 3.5% 3.5%
Sodium- 2.3%
Magnesium- 1.7% 1.7%
Calcium- 0.04%
Titanium- 0.02%
Potassium- 0.01%
Moisture- 7.8%
pH - 8.3 - 9.1
Name
Bentonite clay is the name given to a particular type of clay that was first noted near Fort Benton, Wyoming. This clay was originally called "taylorite" after William Taylor, the man who initially drew attention to
the clay deposits back in 1888. Dr. Sam Knight, a state geologist for Wyoming, renamed the clay "bentonite" in 1898 after he discovered the term "taylorite" was being used in England as the name of another mineral. He chose the name "bentonite" because of the location where the clay is found.
Types
There are two basic kinds of bentonite, and their names depend on the primary elements found in the clays. Sodium bentonite swells when it gets wet, allowing it to absorb a very high volume of liquid. This property makes sodium bentonite an excellent sealant and waterproofing agent. Calcium bentonite, commercially called pascalite, naturally absorbs any oils, fats and oils found in a solution. This type of bentonite clay is the primary active ingredient of Fuller's Earth, which was one of the first industrial cleansing.
How does it work ?
Bentonite is very unusual in the fact that once it becomes hydrated, the electrical and molecular components of the clay rapidly change and produce an "electrical charge". Its highest power lies in the ability to absorb toxins, impurities, heavy metals and other internal contaminants. Bentonite clay's structure assists it in attracting and soaking up poisons on its exterior wall and then slowly draw them into the interior center of the clay where it is held in a sort of repository.
To state it another way… "Bentonite is a swelling clay. When it becomes mixed with water it rapidly swells open like a highly porous sponge. From here the toxins are drawn into the sponge through electrical attraction and once there, they are bound.
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