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Low compaction of crushed limestone/fines

Low compaction of crushed limestone/fines

Low compaction of crushed limestone/fines

A technician used a nuke on a material known as Ab3 or crushed limestone with fines. It's basically a collection of aggregates with a varying gradation and low plasticity. It's used in areas to improve stability of pavements or foundations.

The technician had failing tests of the 132 psf proctor and failed to retest before more material was placed. So they need to do another type of test to get more data to prove compaction of the material. Would a Wildcat DCP test be feasible? Further nuke testing is not possible.

RE: Low compaction of crushed limestone/fines

How bad were the failing tests? How thick is the limerock? This material will tend to bridge and give a false sense of stability.

I would remove the pavement surfacing and retest with nuke gage or sandcone. Any other method would be a guess...and not a good one.

RE: Low compaction of crushed limestone/fines

Ron- it is actually behind a concrete wall and below slab/footings. The rock is roughly 10 feet wide by 12 feet deep. The tests that fail are 92-94% of proctor. The majority of the fill tested above 95%. They were able to re-test some areas and get more passing tests.

RE: Low compaction of crushed limestone/fines

Stuart1126...considering the depth, I would use a cone penetrometer to check. Hydraulic or DCP would work.

Not sure where you are located, but some limestones/limerocks are not great for static fill such as this, particularly if you have high groundwater or acidic groundwater potential.

RE: Low compaction of crushed limestone/fines

Just to point out, the OP reads like the technician was in error. Maybe yes, maybe no. The onus to provide what's specified is the contractor's however. Don't lose sight of that responsibility.


¡papá gordo ain’t no madre flaca!

RE: Low compaction of crushed limestone/fines

It was a technician error. He entered the wrong proctor value into the nuke and was only reading the percentages and not paying attention to the densities.

RE: Low compaction of crushed limestone/fines

Just an observation - and this goes a long way with technicians AND engineers being newly acquainted with field work - I find that far too many are number writers and not number analyzers. The hope is to find the engineer and technician who always question the results . . . does things make sense . . . and perhaps this is another good example why occasional sand cone tests would be very prudent as a check on nuclear readings - for in the sand cone, it is usually (unless I am that old old dinosaur) hand calculations in the field . . .

RE: Low compaction of crushed limestone/fines

Bet you are not that old, BigH. When i was working as a project engineer,just calling out the soil tech, while standing next to the foreman, to take sand cones gave me 3%-6% better compaction.

Richard A. Cornelius, P.E.

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