Asphalt - Leveling Course

[civilman72]

I am overseeing an asphalt overlay project, where some of the existing asphalt surface has started to show signs of stripping and aggregate loss, along with some damage from snowplowing operations, leaving some fairly large voids on the surface. The contractor has proposed to use a 12' screed to identify deviations in the surface and intends to place a leveling course in areas that show over a 1" deviation. Otherwise, they feel the 2" final overlay will properly fill these voids and not effect the smoothness of the final surface.

Does anyone have thoughts on whether the 1" deviation is an acceptable limit? I'm concerned that even 1/2" to 3/4" voids will be hard to cover with a 2" overlay, but also realize there are limitations in the minimum thickness of a leveling course.

 

[Ron]

When you have surface undulations and damage, placing an overlay on that surface will create one of two situations and possibly a combination of the two....

1. The overlay will reflect the undulations if the laydown temperature is high.

2. The overlay will bridge the issues but result in variable density in areas, particularly if the laydown temperature is low.

 

[DDBPE]

Are the deviations ruts (wheel path) or more like pot-holes?
When we do leveling courses for roads showing signs of rutting, we use a smaller aggregate mix (9.0 mm max. nominal aggregate). Thin lifts using larger aggregate mixes can have placement issues (segregation, aggregate fracturing, etc.). If the ruts are significant, you may have to consider removing and patching prior to overlay as the issue may be deeper than the surface.
Ron is correct, you will have density issue trying to overlay these deviations. Rollers will bridge over the areas and you will not see it until after the it has been subjected to traffic.

 

[dicksewerrat]

Mill and overlay.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[civilman72]

While I agree a mill and overlay is the easiest solution - the failed areas are not that big, mostly just along the seams. I've attached some photos of some of the failed areas. We've had moisture here every day since I first posted, so the void area is filled with water in the photo. For reference, I measured the depth of water in area shown on the photos at about 1/2" deep.

 

[civilman72]

Here's another photo

 

[ACtrafficengr]

I think Dick's mill and fill suggestion is a good one. In those photos at least, it looks like you've got some stripping and raveling across much of the surface, not just the joints. A simple overlay on a weak surface probably won't give you the longevity you want. You could always take couple core samples to be sure.

If cr-804 in your photo names stands for county route, you could ask your state's LTAP or T[sup]2[/sup] program for advice.

 

[civilman72]

Thanks for the input. When you mention a core sample and suggest a weak surface, are you thinking the stripping and raveling may indicate a density issue?

 

[dicksewerrat]

Freeze-thaw is starting to unravel the the road. At a minimum, mill a 3 foot section on the CL , overlay that, then the entire road.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[civilman72]

The 3' mill section makes sense. The first lift of asphalt was placed late in the year, temps were only 40 degrees (F) and lightly snowing. Density was met, but I'm assuming the moisture led to the surface failures.