Laboratory Testing & General Mineral Processing Engineering

Laboratory Testing & General Mineral Processing Engineering

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Wet Sieve Analysis on Placer Soil (2 replies)

GhanaBob
7 years ago
GhanaBob 7 years ago

Because of the clay we are experiencing when washing our alluvial gravel, I  have been advised to perform a wet sieve analysis to record the classification of soils . A significant percentage of particle less than 75 microns will determine the presence of clays. Can anyone help me better understand if this is the proper test to show clay content?

David
7 years ago
David 7 years ago
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1 like by BAUD

Hi Bob,

it is 'fill in the blanks Saturday' so I'll take a go at this one. The -75um marker for clay might be applicable to your specific case but it certainly is not a general method.

You will get a better relative reading on your clay content by using methods of determining types and amounts of clay minerals by X-ray diffraction analyses, as
well as methods of determining water permeability. You look for clay minerals like Kaolin and friends.

https://www.youtube.com/watch?v=hh211b8b5FE

Or get fancy with Qemscan and CEC (cation exchange capacitacion)

CLAY-CONTENT-DETERMINATION-Procedures.pdf

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M
BAUD
7 years ago
BAUD 7 years ago
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The material given by David is very rich and helpful.
Clay is a family of minerals whose grain size is comprised between 1 and 4 microns.

In some applications, this word clay has a wide meaning and characterises a range of grain size adapted to the needs of the sector. Then, it generally means fines or mud.

In sand moulding, they use the notion of "AFS Clay7'. AFS stands for American Foundry men's Society. "AFS clay content" is defined as that portion of a foundry sand which, when suspended in water, fails to settle at a rate of one inch per minute. The AFS clay material is determined by the AFS standard clay test. The AFS clay material consists of clay and material of less than 20 microns in diameter. In other words, it is a mixture of colloid, true clay and fine silt.

In your case, the cut off is 75 microns. So your clay material consists of colloid, true clay, silt and very fine sand of less than 75 microns in diameter. This can have some meaning as your main product is gravel.

As said by David, the 75 microns cut off for clay might be applicable to the gravel case, but certainly is not a general method.

As in "AFS Clay", having a qualifying adjective for this "gravel" clay will improve communication.

Clay_fines.pdf

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