Oversized material with proctors

[mjbrown]

Good day all. Have encountered a few gravels this season with very high oversize values of 50-70% and I am just curious to see what other techs are doing with this sort of material to test it for maximum density. Thanks in advance.

 

[oldestguy]

The US Bureau of Reclamation has in the past printed a set of standard tests that include testing materials. Their old "Earth Manual" likely is not current and has a method, but I suggest going through the on-line info that they have to find a current standard for laboratory compaction tests on materials with plenty of gravels. They had used a large mold so that no correction would be needed and had a large compactor to do the compacting. The usual corrector methods with smaller molds do not apply to your situation. Fracturing of the large particles can make a big difference in what kind of field evaluation is done. If getting no where with an on line search, I suggest a phone call to their lab.

 

[cvg]

USACE EM 1110-2-1906 appendix VIA has a method with a 12 inch mold for rock sizes up to 2 inches

 

[mjbrown]

Thanks for you replies guys. A big help.

 

[fattdad]

You do a proctor in a mold, get some value at some moisture content. The ASTM defines four methods and if there's a lot of coarse-grained materials, you'd be using method D. That's based on minus 3/4-size material. Let's say there is actually another 20 percent of material that's greater than the 3/4-size.

What you'd then have in the field is 80 percent of your material with some idealized maximum dry density - let's say that value is 120 pcf. You'd also have 20 percent of the material that'd have a greater density - some density based on the specific gravity of the soil grain. Well, we can know the contribution of these particles to the overall density 'cause these particles are not affected by compaction moisture content. If the specific gravity of the soil grains is 2.7, that'd mean the 20 percent of oversize material wants to be at 168.5 pcf. So, in the idealized state of 100 percent relative compaction, you'd have 80 percent at 120 and 20 percent at 168.5, which would return a maximum dry density of 129.7. This would relate to the condition of compaction at the optimum water content. Now the procedure is a bit more elegant that that, 'cause there'd also be some adjustment to the optimum water content. Refer to D698 (ASTM) for more context and referenced standards.

f-d

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