Specification for Compaction of a Dense/Open Graded Aggregate(#78)?

[Orangecommander]

I've been looking on the forums, and am aware of the discussions that you've had regarding compaction of aggregate fill. The usual recommendation for compaction seems to be requiring placement in lifts of a ranging depth, and then passing over a couple times with some kind of tamper or vibratory compactor.

Is there some kind of standard specification for this? I'm also looking for a test to ensure that the aggregate has reached it's maximum relative density, but it seems very difficult to measure this in-situ. The closest test I've come across appears to be the sleeve method (ASTM D4564-08), but it isn't ideal for this application either.

Any help on this matter would be greatly appreciated.

 

[Ron]

If you want to achieve some quantification of a particular density, I would suggest you use the relative density criteria with the in-place density determined by the rubber balloon method or use the sand-cone-density method but you'll have to slightly modify the method by lining the excavated hole with Saran wrap or similar so that you don't lose sand particles in the voids.

 

[molerat2210]

Ron: does anyboby really use the rubber balloon method anymore? That has not been used since the 70s. Sand cone would not work in open graded stone since the hole would cave-in.

Open graded aggregate fills are usually tamped in layers (18 inches thick) to consolidate. A plate tamper can be used for this purpose. There is no practical method for density testing in the field for open graded aggregate.

If density of the stone is that critical then use dense graded aggregate.

 

[Ron]

Molerat....occasionally still used, particularly for special use applications such as this. The method is still a valid ASTM method, reaffirmed in 2008 (ASTM D2167). The equipment is still sold, but is called a "Voluvessel". (Humboldt, TestMark, Gilson, Myers and Durham-Geo all sell it)

Using a plate compactor for an 18" lift of anything is not advisable. They are light and have little depth influence, so the lifts should be much thinner than that.

As for the sand-cone, you will note that I said you would have to modify the sand-cone hole by lining with Saran wrap. This works fine and doesn't introduce significant error as the repeatability of density testing in open graded aggregates is not as you would expect in typical soil or soil-aggregate mixtures.

 

[molerat2210]

Ok Ron. Thanks for the education. I believe you on this. The plate tamper does work though (about the same as pounding with the excavator bucket). Obviously, does not work for dense graded stone.

 

[Orangecommander]

I don't believe Ron is saying that tamping won't work with dense graded stone, but rather that the lifts that you use it with should be smaller.

Would 8" lifts be sufficiently thin for the plate compactor to penetrate with this aggregate?

 

[Ron]

OC...yes