thread261-445671 You can't get 105

[Testguyaugusta]

thread261-445671
You can't get 105%. That's a bad proctor, gauge, or user error and maybe a combination of all three.
I've spent too many hundreds of hours behind rollers running densities trying to get material to 100% with a good proctor. Most companies won't even accept a 105%. Only someone without the practical hands on knowledge and thinks theoretical is reality would say that. Every tester worth his salt knows you can't hit a 105% with an accurate MDD. Check your moisture, calibrate with a sand cone and make sure your depth is correct and no offsets are plugged into the gauge. Run a one point if you can, take the material under the gauge from where you did your shot back to the lab and run another D 698 on it.
A 105% is just testing 101, first day stuff you learn to know you've got a bad proctor. Never once in thousands of tests I've done has a 105% been real. Drawing it on a curve on a screen isn't the same thing as actually making it happen in the field.

 

[TigerGuy]

Respectfully disagree. The MDD is determined by applying a fixed amount of compactive energy to the sample in a mold. It is possible to exceed 105%, although very rare. It just takes more energy, usually more than the grading contractor is interested in applying.

If I ever see test results in the 103-105% range, I ask lots of questions of the gauge operator. Usually, they had some rock in the test area that was not considered in recording the results.

 

[geotechguy1]

Some points to consider:

[ul]
[li]The energy level for these tests was set based on 1930's-ish era construction equipment. [/li]
[li]I find it important to say 'SPMDD' rather than MDD. It's not the actual maximum dry density, it's a maximum dry density at a certain energy level (the energy imparted into the soil by a standard proctor test)[/li]
[/ul]

Try compacting a lift with a fully loaded ultra class haul truck . You can also compact a 1m loose thickness lift to 95% ( will be likely over 100% at the surface) with a loaded ultra class haul truck. You can probably get over 100% SPMDD relatively easily with the biggest rollers made by CAT etc.

 

[Testguyaugusta]

TigerGuy & geotechguy1 - I agree.

I'm not saying it isn't possible to compact a standard proctor to a modified value. Any operator should be doing a depth check to confirm they're not into different material, that's an excellent point. But, that still makes my point. If you see a 105% something is wrong. You've likely got a bad proctor 9 times out of 10. You could be in different material, definitely. You don't see 105% because contractors just aren't going to spend the time and money to do it. Could they ? Maybe, like Geotechguy1 said, with the right equipment. The thing is, there comes a point of diminishing returns on the effort, the densities just flatten out, like with asphalt.
If you're comparing a modified effort area to a standard effort area, wrong proctor. Get into different material, wrong proctor. If you're using a one point family of curves, you're likely to see a 105 but again wrong proctor.

The original thread was about a guy who had a 105, people were telling him, that's normal because theoretically it could happen. As an operator of a gauge with thousands of hours experience I'm saying, if you see a high compaction like that in the field and turn it in you're going to get questioned so don't do it. Check your moisture, do a sand cone if you're not sure. But, most of us operators just assume 105% may not be right but it's still above the margin of error for normal gauge corrections so it's passing and we pencil whip a decent compaction not to get our phones ringing.

 

[MTNClimber]

TestguyAugusta - the original poster said they were getting 100-103%. Ron said that’s fine as long as it’s less than 105%, as it’s likely an indicator of a change of material that does not match the proctor.

The OP said the material was naturally at 7 or 8% moisture. Optimum was 9.7%. That’s pretty good and with proper lift thickness and compaction effort. Results in the 100-103% are not shocking.

I don’t disagree with you with wanting to check the proctor or nuke gauge but it’s definitely plausible to get that kind of result under the right conditions.

 

[GeoPaveTraffic]

105% of a Proctor is very possible. It does not mean that something is wrong.

Think about it. A Proctor value is simply a max density for a given amount of compactive energy at a given water content. If more energy is put into compaction than the Proctor value energy, then the resulting compaction will be higher than 100%. It is just that simple.

It is fairly uncommon to get much more than 100% of a modified Proctor, but it is very common to get more than 100% of a standard Proctor value.

 

[geotechguy1]

Another point to consider is that the technician should be able to make some judgement calls based on experience, by which I mean:

A 300mm loose lift compacted with a 100kg plate tamper to 105% SPMDD? Something is wrong with the proctor.

A 150mm loose lift compacted with a 1,000kg plate tamper to 105% SPMDD?

Another thing to consider is what the air voids are. North American style specifications don't tend to include air voids but you can get some idea if the proctor is wrong from the air voids. If you are reporting over 95% SPMDD air voids should be around 10%; if it's actually 105% SPMD I'd expect the air voids to be 5%, maybe less.

>As an operator of a gauge with thousands of hours experience I'm saying, if you see a high compaction like that in the field and turn it in you're going to get questioned so don't do it. Check your moisture, do a sand cone if you're not sure. But, most of us operators just assume 105% may not be right but it's still above the margin of error for normal gauge corrections so it's passing and we pencil whip a decent compaction not to get our phones ringing.

An uncomfortable reality of the business is that new proctors take time which costs money - the contractors possibly alot of money if work were to be stopped or rework required - and if this happens regularly, your firm will be out of work. Some engineers will generally expect you to take the liberty of fudging the numbers a bit (while also taking another sample for a proctor test) to avoid awkward looking paperwork.

 

[TigerGuy]

And we've all seen the projects where the entire library of test data indicates compaction of 110-135 percent, because the poor guy in the field didn't know any different and nobody checked in on him. Too often, they think the job is to record the numbers from the magic yellow box and not think about anything.

 

[BigH]

For me, one of the main concerns is that the test result lies below the Zero Air Voids line. ALWAYS check where the result lies . . .

 

[dirtsqueezer]

Just an x-soils inspector here. I agree that it's true that compacting soil will lead to an <100% value on a density gauge. However, here in the Pacific Northwest there is the rain most of the year, and that leads to consolidation in addition to the original compacted density. I have tested soil that came up 98% and then re-tested it a year later. The Troxler gauge at that time read 103%-104%. I know we are talking compacted density, but there is a further possibility of getting a reading over 100%, as I have had experience doing, though it wasn't reached by compaction, rather more likely consolidation. Just my two bits.