Calculating yield during a bituminous paving operation 1

[schumi7xwdc]

I'm starting a new mill and overlay project, and I've never calculated the yield of hot mix per truckload, if anybody has experience with this, please let me know how its done. I think it has to do with Lbs. per sq. yd. per inch times length of paving per truckload, meaning a truckload of hot mix has to be able to go so far?

 

[Maury]

Compacted blacktop varies in density from 112 to 120 pounds pr square yard per inch of thickness. The distance a truckload will cover is something you will need to calculate, it's not a starting point. The starting point is the weight capacity of the truck, then use the paving width and thickness along with the density to estimate how far a truck will cover.

 

[schumi7xwdc]

Thanks, the 112-120lbs per sq. yd. rings a bell now,naturally on the truck tickets from the mixing plant, should have tare, net and gross weight, hopefully, I say that because of computer printout, sometimes these do not work properly.

 

[Ron]

The theoretical area yield will be the number of tons of asphalt divided by the maximum compacted unit weight in the laboratory.

For example, if you have 20 tons of asphalt, then you have 40,000 lbs of asphalt, with say, a laboratory unit weight of 135 lbs/cubic foot. That will yield 296 cubic feet of asphalt. For each 1-inch of thickness that's 3556 square feet or 395 square yards of asphalt, 1-inch thick.

For actual yield, use the average field density of the asphalt. If the yield runs high, that means their compaction might be low!

 

[schumi7xwdc]

Are you refering to the Lab density, taking into account percent air voids or the maximum theoretical density aka rice test or AASHTO T209?

 

[Ron]

I'm referring to the lab compacted density, not the maximum theoretical density (Rice Method).

 

[Grouser]

The rule of thumb in Florida is 100 pounds of "normal" asphaltic concrete will cover one square yard one inch thick.(behind the paver, basically uncompacted) Check your paver pass width and lift thickness, then use conversion factor to compute expected pull length per truckload (net tare on delivery ticket). This procedure assumes constant lane width per truckload, otherwise an additional proportion is required(if constant taper). Variable thickness courses are generally paid by tonnage because of the difficulty in determining thickness per unit area.

Paced lengths are usually good enough for placement monitoring. If you have stationing, so much the better. If yield is off, carefully monitor mat thickness, as controlled by screed height, and suggest to operator(s) they correct as necessary.

Yield for pay (sq. yd.) should be accurately measured with wheels and or tape and completed courses should be randomly cored to verify thickness and density.

Cheers

 

[CivilEQuinn]

I found the following link from hotmix.org to be extreamly helpful when I needed to do volume, wieght and area calculations for a paving job:

http://www.hotmix.org/Paving_Area_Calc.xls

 

[JSheehan]

While working for a paving contractor I used to use a factor 17.4 sy/ton/inch of asphalt. So for every ton of asphalt at one inch thick you place, you should cover approximately 17.4 sy, two inches is 8.7 sy and so on. This is an easy but crude way to calculate your yield for each truckload, and we would use this to order the balance of asphalt on the last pass to minimize waste.