Proctor testing of 3/4" clean stone 1

[joeskin]

Does anyone have a clear idea on what standard to use for performing a proctor on 3/4" clean stone to be used in soil replacement? I've heard that the material is to be crushed, etc. Any advice will be greatly appreciated.

Joe

 

[BigH]

Not really sure that a "proctor" is appropriate for 3/4" clean stone. Not sure you would really specify a relative compaction - by clean, I am taking you mean single sized stone without filler. If filler, then it is different. I would use modified proctors if founding structures on the fill or for the granular pavement structure; for general fill, landscaping, etc., use standard but don't overspecify.

 

[cvg]

Relative compaction might be specified at 70% base on the following tests:

D4253-93 Standard Test Methods for Maximum Index Density and Unit Weight of Soils Using a Vibratory Table

D4254-91 Standard Test Method for Minimum Index Density and Unit Weight of Soils and Calculation of Relative Density

I've used this for testing of sand and gravel filter drain layers.

 

[DRC1]

I have not seen a procter for crushed stone. Typically the stone is placed in 12-18" lifts and tamped once or twice. The stone is so much stronger than the soil and is unaffected by moisture content that lab or insitu density testing is not done. We use it in freezing weather to backfill when soil would be impossible. For most applications, it is superior to gravel, but also carries a hefty premium.

 

[BigH]

DRC1 - that's correct; clear crush is pretty well take as "self compacting".
Merry Xmas to all those celebrating it! Have a slice of turkey (or ham, or ...) for me!

 

[Robert168]

If you just follow the procedure of the standard proctor test, you will still get a proctor curve, showing its MDD and OMC.

 

[Ron]

Robert168...not on 3/4" "clean" stone. The concept doesn't hold.

 

[BigH]

Agree with Ron - might be just as well to rod it like a concrete cylinder. Next problem - and even IF you had a proctor - how to test for the in place density? Sand from sand cone would "fall through" some of the stone - therefore, no good. Don't think nuclear would be proper - maybe rubber balloon?

 

[Ron]

Rubber balloon (if you can still find one!) would be about the only method to determine in-place density in this material. None of the other popular methods are going to work as BigH said.

 

[BigH]

Ron - I learned on the rubber balloon - what a trip that was. We used the Ontario method of one point field estimation - with a precalibrated dip stick. Would get the volume of the "hole" in situ - add or dry the material collected to "optimum" - really, at the in situ moisture content. We would then compact, on site, into a proctor mold the soil collected. By knowing the volume of the in situ hole, there was a correlation to how many blows per layer to use. We determined the volume in the mold (Vm) and compared the in situ volume (Vis) to the mold volume - and you get the percent compaction! ( = Vm / Vis ). Would take about 1 hour per test point to do. Why we did very few of these on site. Better to use the "heel test."

 

[Robert168]

I think the maximum vibrated density is to be used in this case. However, it does not always work in reality.

I did a few maximum vibrated density test for the similiar materials by the dry method, and the results turned out to be quite low(the wet method may yield higher density). There was no obvious change in density after vibration.

The "maximum dry density" by the proctor method was higher than the vibrated density, and it made more sense in that the stone in field after being dumped demanded vibration or compaction to reach a certain percentage of this "MDD".

I agree with BigH in that the nuke can not be used to measure the density of the clean stone accurately due to the air existing in the voids. However, by practice, I found that it can respond to the degree of compaction of the stone, i.e., the more the stone is compacted, the higher the density is.

 

[Ron]

The problem with such gap-graded material is that there is very little unit weight difference between the max and min densities. The void ratio is so high that you have no opportunity to change it proportionally by a very large amount.

BigH....can you imagine trying to use the rubber balloon these days with costs being what they are? You'd have to charge $40 (US) per test! Can do a bunch of nukes in the same time!

 

[BigH]

Ron - Yo comprendo; and likely more when you factor in the going to and from and the milage to the site. - and how about here in India for the sand cone. The contractor has (a) two guys to scoop out the hole - one is in charge of setting the plate and the other to scoop out the hole (b) one guy to weigh the sand (c) one guy to do the speedy moisture test, (d) one guy to write down all the numbers and (e) one guy to use the calculator - sometimes he is (d). Oh, and then there is the one inspector. Figure out THIS cost!