Re: Adding Clay
Here's a question to all of the "CLAY" people out there with clay questions.
When you say "CLAY",are you sure you know what your talking about?(not meant
to be condescending) Let me explain......I work in the construction field as
a soils engineer/geotectnical consultant/inspector/slave...and have a B.S.in
geology.EVERYBODY is the field calls silt -clay.They call any
thick,plastic,fine grained soil a clay soil when in fact 85% of these soils
are silt.There is actually very few clay soils here where I live but if you
ask around they'll tell you differently.
Now i must admit that i'm certainly not up on Agricultural definitions of
clay or clay soils and its probably different.But I believe that the physical
makeup of real clay is what creates the holding capacity of the soil...that
in fact the silts will make the soils look like clay soils but w/o the
advantages of the clay.As far as I know a sieve test(where you shake a given
soil through various sized screens,weigh the particles held back on a given
screen,and compare that weight to the total weight of the sample as a
percentage) cannot and willnot give you an accurate value for clay.The 200
screen so often used in site spec work screens out both silt AND clay.Further
testing is required(involving distilled water,settleing rates etc...) to get
the clay percentage.(It takes a couple of days for this test alone).
Soils are made up of various sized grains...a lot of silt will make your
soils pack,puddle,and impervious too.I just think if anyone has a
"scientific" size definition of the clay we want it would be helpful to us
all in cleaning up some questions.
An added note: most of the time the terms clay-silt-sand-gravel-etc are ONLY
size definitions.....perhaps we're really looking for chemical compositions
as well as size?
also-I believe BENTONITE to be a resultant material from the further
breakdown of volcanic ash....but I got my geology degree before the last
iceage so things may have changed or my brain might be dead again......Glenn
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