Need clarification on pavement thickness definition - HELP!!! 4

[kashley1229]

I am working on a asphaltic concrete overlay design. The funding limitation is 1-Inch of asphalt for the overlay. This presents a problem because Aggregate for Superpave is set at 1-Inch Minus. It's impossible for the paving machine to lay down only an inch of 1-Inch material. So...my question is this:

Is one inch an inch layed down or an inch compacted? I have looked at the FP-03 (That's our standard) and can't find that specification.

Somebody help? Please?

 

[ACtrafficengr]

I think you're looking at the wrong type of pavement. NY's superpave specs call for 1/2" minus or 3/8" minus aggregate for top course. 1" minus is binder course.

I've always thought the lift thickness was after compaction.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

 

[Ron]

First of all your limitation is absurd from an engineering standpoint. Even using 3/8" top size aggregate, that's a pavement overlay waiting to fall apart.

To answer your question, the pavement thickness is based on compacted thickness, since the design properties are based on compacted materials.

I understand funding limitations, but you have an obligation to design something that is workable from an engineering perspective. Run the numbers and you'll find that theoretically you can probably get a 1" overlay to be sufficient for some increase in life expectancy. What the numbers don't tell you is the performance and constructability of the design decision. I would not specify a 1" overlay of any type of asphalt for a wearing course. You can use it for a leveling course, but not wearing.

 

[ACtrafficengr]

Ron's got a good point. One rule of thumb on overlay life expectancy is cracks will propagate through at a rate of one year per inch of thickness.

Given the budget limitations, perhaps you would get more for your money (but less political good will) by maintaining or upgrading drainage.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

 

[Drumchaser]

Lift thickness is after compaction, before compaction dense graded mix is usually estimated at pounds per SY.....110 lbs/SY = 1" compacted...usually.