Atterberg Test

never heard of running atterberg limits on just the minus 200. Not sure of the value. I'd just follow the ASTM standard for Atterberg limits and use those values.

f-d

¡papá gordo ain’t no madre flaca!

These standards call for separating out the fraction passing the Number 40 sieve (in USA at least) and running plasticity tests on that. Before getting too involved, you probably should look up soil classifications in your area, since there are specific meanings for what is clay, silt, sand, etc.

If you are running Atterberg limits, it's a good bet that most of your material is -200. I would not separate the sample to run AL. Keep the sample intact...that's the only way the results can be properly interpreted.

I agree that you should generally run it on the portion passing the nber 40 sieve. But you should also consult the people asking you to run the test. If they are knowledgeable engineers, they may want the test on the minus 200 portion for a specific reason. On the other hand, if they are just uninformed customers then you should kindly try to educate them.

For any interested, BS Standards (BS 1377 Pt 2) also is done on the minus #40 sieve as well. Yes, I know that BS is not standard anymore - it is now European Norms (EN) but don't have their soil testing specs.

My question is this for the minus #200 fraction. I don't suppose you are required to separate the P200 out with a dry sieve method. Otherwise a wet sieve method probably is in order and then what a time drying the result and then trying the Atterberg limits. Did it all pass the sieve or are some small clods still on the sieve? All that playing with it is likely to change the characteristics. Either way sounds unrealistic.

The biggest problem I've encountered with doing and reviewing Atterbergs (and I have done many) is that the tech is not really diligent about making sure that ALL of the material that is chosen for the test that CAN be broken down IS broken down for the test. What happens is, the tech gets complacent and leaves a few hard clods that he struggles with. Those clods that are hardest to break down may contain higher plastic materials that can seriously skew the results. Make sure that the material retained on the #40 is "retained" for later review. For that reason, I am very careful in splitting up the sample and make sure to limit the amount to just what is needed for the test.

This would be a much more compromising problem if one was to break down the material over the #200. The test procedure and the interpretation of the test should be carried out according to the accepted standard of the jurisdiction you are working. Any deviation from that standard needs to be stated in the report. I can't imagine using a wet sieve method to breakdown the -200.

It should also be pointed out that doing the test by starting out at insitu moisture content is possible and is often preferable. Just make sure to sieve a representative portion to confirm that there is little or no material that would otherwise be retained on the #40. This method may ruffle some feathers, however, I have done comparisons using both methods and have achieved good, repeatable results.

If the soil contain majority of sand, then it will act as sand (drained material) when subjected to loading. Index property of minor constituent does not help infer the behaviour of the sample, unless -200 is significant enough.