Determing Maximum Dry Density with 3" maximum aggregate

[RoosterPE]

I am currently working on a project where the proposed material to be used is a 3" DGA mix (modified stone with 3" aggregate) for fills for a project. Per the Geotechnical Engineer belonging to the owner, the material must match a certain gradation and subsequent proctor performed on the material. The proposed material as mentioned before is a 3" densely graded aggregate, however, with both the modified and standard proctors, this material doesn't meet Methods A-D of both Standard and Modified proctor methods as the amount retained on the 3/4" sieve exceeds the threshold.

I do understand that there is a method in USACE which I have researched which allows for a 12" mold and up to 2" aggregate maximum. However, I cannot find a method for material this coarse to determine the maximum dry density and optimum moisture given the 3" maximum aggregate.

Is there another method to determine these parameters as the Geotechnical Engineer belonging to the owner is hanging their hat on compaction testing via the Nuclear Method ASTM D6938.

 

[GeoEnvGuy]

The proctor method takes out the coarse gravel and determines the compaction curve of the sand fraction and is then adjusted for gravel content. If most of the material is gravel then a proctor is not appropriate. Nuclear tests in coarse gravel can be done if there is sufficient sand size, if there isn't then results won't be reliable. In which case you're better off with a method spec for compaction or compaction test strip method.

A shake table test can give you a number for min and Max density, if required.

 

[fattdad]

If you run a proctor in a 12-in diameter mold and that test supports a 2-in maximum size, you are almost there! Run that test!

Now in the field, you'll have a problem. The soil being tested may have material greater than 2 in. So, after the field density test, dig out the soil and determine the plus 2-in percentage. Let's say that there is 12 percent oversize. That means 88 percent of your field density test was on material like the proctor!

Do some math and calculate the percent of relative compaction for that 88 percent. All it takes is some sense of the specific gravity of the oversize materials.

f-d

ípapß gordo ainÆt no madre flaca!

 

[GeoEnvGuy]

ASTM for Proctor and modified proctor says to use the shake table for free draining material. ASTM D4253 Test Methods for Maximum Index Density and Unit Weight of Soils Using a Vibratory Table

"This test method will generally produce a well-defined
maximum dry unit weight for non-free draining soils. If this
test method is used for free-draining soils the maximum unit
weight may not be well defined, and can be less than obtained
using Test Methods D4253."

The shake table ASTM also mentions that you can get a higher density using the vibratory hammer ASTM D7382.

"These test methods will typically produce a lower
maximum dry density/unit weight than that obtained by vibrating
hammer using Test Method D7382."

To be honest I do not think the geotechnical engineer is expecting you to use these alternative methods as nuclear tests wont perform if the proctor doesn't perform.

 

[fattdad]

To GEG, The OP says it's a dense-graded aggregate at 3-in minus. That will not be free draining.

To the OP: I worked on a job where they demolished the old prison. Big 3-ft thick walls. They crushed the brick and used it for fill. The size was like you are talking - likely 3-in minus. The company made the world's biggest sand cone and we ran the job on a maximum dry density spec. There is no reason you cannot use field density testing, you just need the right Proctor and a field test method.

You can also make a test fill and produce a method spec.

f-d

ípapß gordo ainÆt no madre flaca!