Opening PandoraÆs box

[jjf1]

Maybe someone out there can help…………

We have a very large asphalt paved parking area installed circa 1935. It is surrounded on three sides with streams and creeks and is in an area with a high ground water table (+/- 4’ below grade)

The parking lot is well graded and rarely held any standing water.

Now, here’s the problem.

It was decided to replace the pavement, as the surface cracking and spalling was becoming a problem. When the first area was opened up, it was found that no sub grade preparation had been made and area was basically paved over (rock, clays & organics). It was decided to remove all the “soft stuff” and replace with “hard stuff”. Of course the contractor is claiming everything is “soft stuff” and he has to dig it all out (in some cases to 5’ deep) and of course the delays associated with all this work.

Our geotech support has been limited and we are addressing that problem.

Here is the direction we are headed…….please let me know your thoughts:

In the uncovered areas, fill and compact the areas to a depth of 12 below existing grade; place geotextile fabric; fill and compact with graded sand/stone to a depth of 5” below grade (7” of roadbed fill); top with 5” of coarse asphalt, bringing the area back to the original elevation.

Cap entire area (both opened area and existing pavement with geotextile fabric and then 3” of wearing surface asphalt (placed in 2, 1 ½” lifts)

Opinions, thoughts, suggestions appreciated.

jjf

 

[bltseattle]

Sounds like this was maybe historically a wetland. As such I would be concerned with differential settlement between your improved subgrade areas and the existing pavement. One way to minimize differential settlement would be to check that your proposed section essentially matches the weight/loading of what was there before. If not, consider a lift of lightweight fill such as "hog fuel" (cured wood chips). You might have to overexcavate more than 12 inches to fit in the lift, since you can not pave directly onto hog fuel.

 

[BigH]

I am amazed that the parking lot asphalt lasted near 70 years!!! The cracking and that is problably just from severe aging. I would have thought that you would have just simply removed the existing asphalt, after finding the soil conditions beneath, add a 4 to 6 inch layer of crushed stone and then put on your new asphalt wearing course. Great performance to date; sometimes trying to do the "right" thing ends up mucking up the "working" thing!!

 

[boffintech]

Any plan of remedial measures should be tested first with a control strip to verify desired results. You could simply remediate a section and then proof roll it to see if the results are satisfactory.

 

[cvg]

If the pavement held up so well for 70 years with no subgrade prep, why the improvements now? Will the traffic loadings be increasing greatly? You have 8 inches of AC over 5 inches of agg base - that seems like overkill for an ordinary parking lot.

 

[Prepakt1]

Prepakt,
its not advisable to fill with sand if you have running water.

Intrusion Prepakt

http://www.marineconcrete.com

 

[jjf1]

Thanks for the great feedback. Yes a simple repave would have probably worked just fine.

But we've all been in situations where the "solution" is developed before all the facts are in.

Thanks

jjf