Any recommendations for poorly compacted Asphalt?

[JasonG]

A 4" thick (2" base/2" top coat) asphalt parking lot was constructed last winter in New England. Subsequent lab testing of core samples revealed air void content above DOT specs and compaction below DOT specs. Areas where the air voids are highest and the density lowest are visible on the surface.

We suspect that the temp. of the mix may have contributed, at least in part, to the poor compaction. The work was not inspected during the construction so no data is available. However, we do know that the air temp. was below freezing when the base was laid and about 50 deg. F when the top coat was laid.

So the question is what does this mean and what can be done to remedy the situation? Will this parking lot rapidly deteriorate or can it be expected to last 10 or 20 years? Does it need to be torn up or is there another alternative?

Thanks for any input you can give.

 

[BigH]

JasonG - please state the air void contents achieved; the compaction achieved; the design details (e.g., Marshall design - design air voids, etc.) Also the "DOT" values you are using - is it against Rice Density or Marshall Density. On our project, the specs require overcompaction and lower air voids which, in the environment we have, leads to flushing and rutting. For you, it is a parking lot - not a highway. Keep this in mind; you will not be having big 18-wheelers driving about at 100/hr.

 

[JasonG]

The actual % air voids range from 5% to 14%. The DOT specs are 3% to 5%. The actual % compaction TMD ranges from 87% to 94%, the DOT spec is 95%. The TMD was determined using the Rice Test.

Thanks for your help.

 

[BigH]

Normally the 3 to 5% is "taken" as the void ratio at 100% Marshall for road design. Sadly, this does not take into account secondary compaction that occurs. The compaction level is usually chosen to achieve an air void of 6 to 8% at the time of primary compaction - given, then that secondary compaction would be about 2 to 3% (heavy trafficked roads), you will get >3% after secondary. This has implications of minimizing flushing and rutting. Typically you would compact to a minimum 96% Marshall which is equivalent to about 92% Rice density. Some jurisdictions say that the compaction is the "average" daily compaction based on all the cores; others hint/say that it is the single core minimum. The DOT Rice density at 95% seems quite high. Are you sure they mean Rice and not Marshall? Again, you are not building a road - but a parking lot. Very low compaction might mean potholes but your overall pavement distress will probably be a reflection of environmental factors (frost, etc) rather than loads. I wouldn't apply a roads spec to a parking lot seeing only cars and occasional truck.

 

[emmgjld]

JasonG,

As BigH has requested. More information.
The full specification is required. Is this a Marshall design or a Hveem Design (like Superpave, using a Stabilometer)? Is this using the Marshall or Rice as the basis for max. density.

Also the subgrade conditions and section design method will have some bearing (pun intended)as to weather the existing material may suffice. If the section requires a wear surface of asphalt (strong, stable subgrade) vs. the asphalt provided a large proportion of the pavement strength (soft or unstable subgrade).

 

[jimbo]

I would NOT expect the lot to last 10 years in a satisfactory condition. (I spent many years in parking areas design & construction.)
jimbo

Buy a dictionary, keep it nearby and USE it. Webster's New World Dictionary of American English is recommended, and Webster's Collegiate Dictionary.

 

[CarlB]

If determined that the low compaction is not acceptable, would a 1.5" asphalt overlay be an option?

 

[dicksewerrat]

Are the bad areas fairly small? Or do they look like an entire pass with the paving machine? If small, cut them out and patch. larger areas could be milled and replaced. An overlay will reflect the bad base in a few years.

 

[JasonG]

Thank you for all of your input. To answer some questions:

1) There aren't really any defined areas that could be identified and replaced. There are some visible spots but not enought to delineate the problem areas. It's pretty spotty.

2) There is no design specs for this project. The contractor used standard DOT details, which is what's typically done in Rhode Island.

I guess the most critical thing I need to know is should my client be concerned and try to make the contractor tear it up and redo it or is it "good enough for government work" as is?

 

[RDK]

I’d lean towards having the contractor tear it up and replace it with a product that meets specification.

You can ask for an extended warranty but that will only be good as long as the construction company is in business. Lowering the payment may allow the client to assume the risk and have the funds to replace the paving at some time in the future.

In any case it should be the client’s decision, put the options in front of him and let him make the final decision.

However my recommendation would lean towards remove and replace unless the reduction in payment was substantial (50 to 75% or more).

If the pavement fails in 5 years then the client will never remember your caveats on accepting the pavement but will remember that the construction product that you specified and inspected did not meet the requirement.

Document yourself very carefully for the possibility of a future law suit.

Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com