40mm asphalt over a concrete pavement

[marrrkie]

Our company has been contracted for asphalting works and in some parts this includes laying a 40mm thick layer of wearing course asphalt directly over concrete without any aggregate beneath. This method is new to us and I am not convinced this will work given:

1) concrete beneath is cracked
2) where will any water that may find its way through the black top layer drain to?
3) asphalt layer, given it is the only one, is too thin.
4) There may be other problems I am not seeing...?

We feel we are to point out, that as contractors, we are not willing to take responsibility for any damages other than bad workmanship as we are unsure of the design, but we do not know if we are on the right track...

Grateful for any tips...

 

[Ron]

40mm is very thin to do what you are attempting. Just the variations in the concrete surface from the cracking will give you problems.

You will get reflective cracking through the asphalt and it will show rather soon in such a thin overlay.

I would recommend rubbleizing the concrete prior to placing the overlay. At the least, the concrete should be cracked and seated, but a thicker overlay will be necessary.

Has anyone put any design thought into this pavement section?

 

[ACtrafficengr]

If it's not too badly cracked, diamond grinding the existing concrete may be a better approach to smooth out the bumps and remove any polishing.

 

[MiketheEngineer]

If you are in the asphalting business ---- aren't you the experts on this stuff??

 

[Drumchaser]

Is this a parking lot or city street? Highway?
What is the concrete?....thickness? reinforced conc. pavt.?

 

[dirtydigger]

Some producers will tell you that their material will survive at 40mm thick on cracked concrete, mainly because they alter the grading envelope slightly and heavily modify the binder. In my experience this does not work as well as they say it will.

Polymer grid reinforcement does not work a this depth below the wearing course, so is out. Depending on the traffic flow, you will need to increase the asphalt overlay considerably to ensure any kind of design life, with at the very least a binder course included.

Have you had any FWD/LWD survey of the concrete?

Iain