2.5" deep AC & Overlay project 2

[lidabc]

I have an AC overlay project for an old Park parking lot.
I checked as-built plans and found that the depth of the existing AC is only 2.5" deep.

It gives me a concern that 1.5" deep grinding would "BREAK" the existing AC so it might cause repeating the same job in the near future.

The owner mentioned that they have a limited fund available only for overlay works rather than replacing whole pavement. The size of the parking is a little over 1 acre.

What would be an optimum solution for this type of AC overlay job that a good civil engineer can advise?

Any information or advise would be highly appreciated.

Have a wonderful day.

 

[Ron]

What kind of base material is under the asphalt? Why do you need to mill 1.5" off the existing surface? Why not mill 0.75" and overlay 1.5"?

Another possibility, if you don't have a good base material, is to use a "mix-in-place" recycling method whereby you break up the existing pavement and mix into the base using a Reclaimer. Asphalt emulsion can be injected at the time of mixing to create a very good base material, then you can overlay with a minimal wearing course (1.5 to 2"), assuming your traffic loading is low.

 

[civilman72]

Trying to mill off 1.5" from a 2.5" layer will more than likely not work, and will cause the asphalt that is left to break apart.

Ron has some good points. Why do you have to mill 1.5"?

 

[roncity]

What shape is the existing surface in ?
Unless there is extensive rutting and cracking, it may be better to forget all milling and just overlay what's there.

If you have to match surface grades ( like at drainage inlets , gutters and driveways) it may be cheaper and faster just to spot mill along those edges.

 

[lidabc]

Thanks for all your comments.

The existing pavement (1.25% slope)have cracks several areas so milling is needed before overlay.

I might reduce the depth of milling to 1"

@Ron
I don't know much about "mix-in-place" Is there any benefits on cost and construction schedule? It would be great to have some more info regarding "mix-in-place"

Thanks-

 

[TGLG]

If the existing pavement is in good shape, leave it in place, repair any bad spots, and overlay the entire pavement.

If the existing pavement's in poor condition, consider pulver mixing, as Ron suggested above. In this type of operation, the existing pavement is pulverized in place by a milling machine (Bomag makes the machine, so around here the contractors call it "bomagging"). The resulting material is then proof-rolled and used as a base course for your new asphalt.
We've done this on a few commercial sites and have had good results.

Of course, all of this is assumes good soil beneath the pavement. If the existing pavement is failing due to poor soil conditions you may need to install a heavier/stronger pavement section.