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Bentonite mix testing using Atterbergs.

Bentonite mix testing using Atterbergs.

Bentonite mix testing using Atterbergs.

I am currently testing surface coarse material for a road in Montana. The original material to be used had no PI. It was decided to add bentonite to give the material a PI of up to 7 +-3. Everyone who tests this material gets different answers ranging from 0 to 16. This is the first time I am testing bentonite. I know it is very finicky. Because everyone is getting conflicting Atterberg results, I was wondering if there is a better way to test bentonite mix soils? I heard of a cone drop/penetration test. I just want a more accurate answer so that we can figure out which tester is the most accurate.

RE: Bentonite mix testing using Atterbergs.

You are asking for trouble with bentonite. It is very touchy stuff. Let's suppose there is some problem with getting the exact percentage on the job. Just a shade too much and you may well have an unholy mess on your hands later. If you and the contractor are not used to blending this stuff, look out. Why not look around for some local source of more silty material? Have you looked at blending in some cement? A weak soil cement mix may well do the job.

RE: Bentonite mix testing using Atterbergs.

Behaviour of bentonite will be dictated by its hydratation. If all the lab testers don't follow the same procedure, they can't reach the same results. You should mix water and bentonite first and let it hydrate for 24 hours before testing.

RE: Bentonite mix testing using Atterbergs.

I agree with OG. Perhaps cement mix will be a better solution for your material. Also,I think that there may be more references for cement treated soils than bentonite mixings which will allow for more consistent testing results since guidelines are defined better.

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