DGA Payment via Truck Weights 1

[tyrone718]

Im paying a contractor via weight tickets of DGA which in turn gets converted into cubic yardage.

I received a max dry density of 125.8pcf and 10.5% optimum moisture content via test made by an independent lab. We are requiring 95% compaction and stating the moisture contente should be 6% +/- 2% based on the dry weight.

The questions are the following:
1)Im getting a density based on loose dry material and the trucked material has some moisture...is there a way to deduct the weight of the water or is it negligible?
2)I keep hearing about fluff factors...is there a way to determine a fluff factor since we are theretically paying for the voids in the DGA and we want to pay for the 95% compacted DGA.

Please advise on the conversions that need to be done so that we pay only for what is required.

 

[Dozerman56]

There will always be some amount of moisture in your aggregate as the quarry has to keep dust under control. The moisture shouldn't be excessive as probably most of their customers aren't getting paid by weight. I'm not sure why you want to have your moisture that far below optimum.

The fluff factor doesn't matter when you're buying by weight, but by volume. Are you telling us you don't want to pay for the additional material if your contractor achieves 98% compaction instead of 95%?

 

[tyrone718]

I just want to know taking into consideration all the parameters per the test (125.8pcf and 10.5% optimum moisture)and the requirement of 95% compaction, what is the conversion from a truck load (in tons per the quary) to a cubic yardage of compacted material.

 

[civilperson]

Assume 5% moisture in the trucked material. This gives 0.59 CY/ton at 95% of the maximum dry density and requires the addition of 100 pounds of water for each ton of trucked material.

 

[reddog99o]

Do yourself a favor in the future. Never touch a project that pays as you describe. There are too many variables and potential dishonesty involved. You've created a contractors dream. In the future, pay by the in place volume as measured to defined neat-lines. I'm a contractor and always request a change to these parameters to avoid muck-slinging as well as my own reputation.
Good Luck,

Rick Hassett, P.E.

R.A. Hassett, P.E.
rah1616@hotmail.com

 

[Nick42]

There is Conversion information out there depending on your material. It is common to convert from excavated volume, to lose volume, and to compacted Volume.

The contractor I work for has data on a number of different materials, though they don't like to share since much of the info has come from historical data within the company. However my point is I know these conversions are out there.

The material in the trucks will me lose volume.

Hope that helps with your fluff factor.

 

[BigH]

reddog99o - good for you! I agree. Even when you do the "unit weight" as per ASTM, you have to decide whether you want the "loose" "rodded" or "jigged". Not easy.

 

[Ingy]

Way to go Reddog990. I agree with you 100%. Pay for excavation by the bank yard, and pay for backfill by the bank yard. Just have those limits properly defined in the contract documents.

Tyrone718. I think you have to be reasonable in how you approach this. I hope you don't expect the contractor to be able to specify the moisture content of the aggregate he is purchasing and to be able to purchase the exact amount. They purchase by the ton, if there is too much water the quarry will hear about it from the contractors. I suggest just taking the scale tickets for the trucks delivered and using them as your basis. Measure in full truck loads. And next time, don't pay by the ton...

As for conversion factors, just about everyone uses the Caterpillar Handbook, Mining and Earthmoving chapter on production. They've got a pretty good approach.

John Engstrom

 

[Dozerman56]

Geez, y'all, I'm a little disappointed. When you buy the material by the ton it's going to occupy a predictable volume. The only variables are percentage of moisture and percentage of compaction. I assume Tyrone specified either standard or modified proctor for establishment of the dga's actual maximum density. Measuring by truckload is how you get into dealing with fluff factors and all sorts of wild cards. There's nothing wrong with paying by excavation and borrow in bank yards. But what's the in situ density of the on site cut and the borrow material? And who's paying the surveyor to section it? What Reddog advocates is lump sum fixed price bidding, and there's nothing wrong with that as long as the inspectors do their job and check EVERYTHING. Either way, if nobody is checking the subgrade with a stringline, there's all sorts of opportunity for mayhem with either system.

 

[reddog99o]

Wow Folks, never did I think that this would go down in the analls of controversial Civil Engineering Issues. It's approching the varied opinions on which way the perforations should be pointed in an underdrain system.

The system as I have employed and will continue to employ regardless of which side of the fence I'm on, requires one major survey, the original bank survey. Then interim surveys per payment period as well as a final survey to wrap it all up. No survey besides the Const. Layout is required at the point of installation as this payment is to the defined neat lines. Other than normal Construction Inspection, nothing additional is required.

R.A. Hassett, P.E.

 

[msucog]

you could go the excavation site, have them excavate a nice and neat square/rectangle hole until the truck is full, measure the hole, weigh the truck (full vs empty), and then see if the calculations are comparable. come to an agreement up front as to how you should quantify everything and go with it. whether you agree on the in-place neat volume, truck volume, volumes including swell/shrink factors, or whatever...set the standard up front in writing. and it never hurts to pay a testing firm money to have someone sit and count trucks all day either. how many trucks would pay for a month of someone counting to make sure you're getting every truck load? (8 hrs/day x 5 days/wk x 4.25 wks/mo x $45/hr = $7,650 per mo--that equals only 2 to 3 truck loads of soil per day...)