Sand Equivalent vs Hydrometer
Sand Equivalent vs Hydrometer
(OP)
I need a "quick and dirty" method to determine clay content in soils. Can the sand equivalent test give me a percentage clay content? Or do I stick with a hydrometer test?
When doing the hydrometer. I have tried cutting back the number of readings so I just end up around the 2 micron and use the wash to determine the fines content. It still is a time-consuming test when all I need is the clay content, not a full gradation curve.
When doing the hydrometer. I have tried cutting back the number of readings so I just end up around the 2 micron and use the wash to determine the fines content. It still is a time-consuming test when all I need is the clay content, not a full gradation curve.





RE: Sand Equivalent vs Hydrometer
I could look up the reference to the standard for you but it would take a little research time.
The method involves putting a small amount of the soil in a test tube and adding a 3% salt solution, then agitating it vigorously, then allowing it to settle. The clay and fine silt content can then be measured and calculated from the layers that can be seen visually.
It's the agitating that does the dispersing of the particles. The saline solution stops the clay particles from going into suspension in the water.
HTH
Michael
RE: Sand Equivalent vs Hydrometer
RE: Sand Equivalent vs Hydrometer
f-d
¡papá gordo ain't no madre flaca!
RE: Sand Equivalent vs Hydrometer
It's for USDA classification of soil for use in septic field applications. We use the test to ascertain whether a soil is sandy loam, loamy sand etc. (shudder).
I know there are agricultural soil testing labs that use a shortened method for determination of clay content, but I'm not sure of the methodology they use.
It is not an engineering application where we use the Modified Unified method for soils classification. For those applications we use the full grain-size chart.
The salt method has my interest peaked.
RE: Sand Equivalent vs Hydrometer
It won't tell the clay percentage, per se, but would help to flag whether the fines are clay or silt, or the predominant clay mineral, which can have a large role to play in its behaviour.
Have a look at http://www.astm.org/Standards/C837.htm