Is anyone really experience with atterbergs on non/almost non plastic soils? 1

[NuzakFarnas]

So I live in basically an old lake bottom so I've got super highly plastic stuff down packed. I'm good with everything from high to low plasticity, but its the stuff that is either non or barely plastic where I have issues. The guy from our certification body has told me that in order to declare something as non plastic you have to test the soil and have the plastic limit come back higher than the liquid limit. My issue is how to actually get 25 blows out of a non plastic soil?

What I find is that it's either too wet where it closes after maybe 6 blows, and then as I dry it, it becomes so fragile that I can't cut through the soil without tearing the soil apart in the cup. I can scrape it away in tiny increments but I still don't find it works. I've tried with the wingless cutting tool that looks like a field hockey stick but even that will eventually cause a slip surface between the soil and the bowl and push one side over... and they also build up huge walls alongside the cut so I think I would trust those results even if it did work. So we end up doing what just about everyone does (I imagine) and just call it non plastic. But this doesn't satisfy the criteria of what our certification body tells us and I've heard of a firm getting sued like crazy for this because they were told to confirm their road base was non plastic and it was found to be very slightly plastic. Does anyone have this no to low plasticity stuff on lockdown?

 

[BigH]

Your guy from the certification body should read ASTM D4318 section 19.1.4; there are two conditions. "If the liquid limit or plastic limit tests could not be performed or if the plastic limit is greater than the liquid limit, report the soil as non-plastic, NP." In my view, it is ludicrous, although some will differ, to do an Atterberg limit on a clean sand. To do so will be a waste of your project's laboratory budget.

 

[emmgjld]

A big thumbs up to the BigH comment.
Low to non-plastic soils have always been a point of contention in the Colorado Springs area and more so on the Western Slope of Colorado. My father went to the Casagrande Tool (I assume it is 'the wingless cutting tool that looks like a field hockey stick') in the late 1950's due to the problems you describe. I still use that tool for most of everything I test. A very high percentage of my soils are CL-ML and the confirmation of these soils in the aggregate base materials and the fairly clean sands can be real important for drainage and potential 'soil piping' concerns.