Roadway Overlay 3

[foley7]

I have a client that wants to overlay and raise the existing asphalt roadway 2 inches. The road was surveyed and the cross slopes vary and roadway profile grades have allot of unnecessary grade breaks. The road meets minimum standards. I think if you're going to spend the money you should make the cross slopes match and smooth out the profile grade by leveling and milling instead of just laying over the existing grades???? Any thoughts??

 

[ACtrafficengr]

What are the ADT and functional class of the road? What is the safety history? How about the operating speed? Are there any drainage issues?

If the road is operating satisfactorily, the benefits of improvements may not be worth the cost.

What is the condition of the existing pavement? If it is mediocre or worse, a 2" overlay will only buy your client a few years before cracks propagate through. If the road is too far gone for an overlay, you might be able to convince the owner to fix the geometry as well as the pavement.

"...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

 

[EngWade]

In a perfect world, I'd agree with you. But it all depends. Is the road functioning adequately or are there problems? How long is the overlay section? How much money is available? All depends...

 

[beej67]

Does the road have a ditch section or a gutter?

Something to think about:

Laying two inches of new asphalt onto a curbed and guttered road fills in the gutter pan, reducing the effective curb height and quite often creating new drainage problems that weren't there to begin with. I cannot tell you the number of times I've seen paving create drainage problems in residential subdivisions, where the curb cuts suddenly become de-facto inlets and water that used to stay in the gutter pan goes cruising down driveways.

Home owners typically aren't savvy enough to realize what's caused their problem, and even if they did there's not often much recourse once the road's been paved, but it's still something a smart engineer should consider when repaving.


Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[foley7]

The road is in good shape except for a few areas where the base has failed. The failed areas will be fixed under this contract. We're extending the road and the money is available to overlay the existing road and fix the base failures. After looking at some cross sections the leveling layer averages 1 inch or less for approximately half of the whole overlay. The road is straight with grass ditches and has a posted speed limit of 25 mph. The grade breaks are not that noticeable when driving however they are noticeable on paper.

 

[foley7]

Everyone..thanks for the comments. I forgot to mention that I'm concerned with milling because of a geotextile fabric that was installed under the top asphalt layer during the last overlay years ago????

 

[beej67]

I'm no expert on milling, but I've seen one of those machines work up close and I can't imagine any amount of geotextile would hinder it in any way. One concern you might have (have to ask an asphalt lab tech) is whether or not you can use milled asphalt as RAP if it's got bits of geotextile in it.

I spent some time in college working in an asphalt lab, but I'm not the guy to talk to. I spent most days shaking rock and pounding out marshal pills.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[Ron]

beej67 is correct...the geotextile won't present a problem with the milling...it might ravel and tear a bit, but not a big deal.



Foley7...I agree. Fix as many issues as you can within your budget.

 

[3feethighandrising]

I'd walk the section during a brisk rainfall. All the existing drainage problems and potential drainage problems from the 2" overlay will be come real apparent during a rain storm. This gives you a good chance to identify any bird baths and any existing catchbasins inlets that are not placed at low points.

 

[foley7]

Thanks for the comments.