Reusing Pavement Millings

[GZ2001]

We have a client who wants to take pavement millings from driveways and a parking lot and use it to create an emergency access road for fire trucks, ambulances, etc. This road would rarely be used for those purposes, probably mostly by ATV type maintenance vehicles, maybe an occasional pickup truck. They want to simply place it and compact it. The question came up if this should be sprayed with a tack coat, or if the compaction is sufficient for a "road" that will rarely be used?

 

[MiketheEngineer]

Not a pro in this subject - but I thought these millings were recycled back to the "asphalt" plant, mixed in with new and resold??

BTW - old roads just were dust?? So maybe yes to you question.....

 

[Ron]

Yes, you can use millings for an "unpaved" or aggregate surfaced road. If you do not embed a layer at the top in asphalt or asphalt emulsion, you will have a very dusty area and deterioration from rain will occur.

Don't use a tack coat....won't do much and will be messy.

 

[Ron]

oops...pushed the button too quickly....

Even though only sporadic use of roadway is anticipated, make sure the material is stable enough to withstand the anticipated loads. Keep in mind that fire trucks are heavy and they create a lot of turning friction.

 

[GZ2001]

Thanks all for the pointers--do you have any suggestions what to use then instead of a tack coat?

 

[cvg]

often done around here by applying a asphalt emulsion re-juvenating layer on top and then rolling to produce a very good and relatively cheap gravel road for light traffic which will not produce a lot of dust.

 

[Ron]

Agree with cvg...asphalt emulsion (in my area, AE200H is typically used) or you can use a cut-back asphalt.

 

[Drumchaser]

I would not recommend a rejuv. agent. If the millings are placed on a decent subgrade (hard layer) and placed and rolled in during hot weather the matl. should slick over and create a somewhat sealed surface. (This depends on the quality of the RAP.)
If the subgrade is not stable, large vehicles will find the weak spots in the subgrade.
As Ron stated turning movements in particular will be a burden on this material.
The problem with placing liquids (emulsions) on top of this material is the potential for tracking due to richness....could get messy....if this area is OK with this and you have someone who is familiar with the material(s) and rate of application....then give it a shot.

 

[Hoaokapohaku]

This depends a lot on the quality of RAP. If the millings were from an old highly oxidized pavement, the resulting road will be similar to an aggregate base and will similarly dust and erode unless somehow treated, like with an asphalt prime coat (not tack coat). If the millings are less oxidized, typical of a highway paving project, after the material is placed and compacted and exposed to the heat of the sun for a while, the asphalt bonds the road together and there will be no dust and minimal erosion.

If some kind asphalt surface treatment is applied, use a lighter grade cutback asphalt, like MC-30 or MC-70, if it is permissible in your area. The key here is maximum penetration into the RAP. There are modern emulsions engineered for superior penetration as a prime coat, but they are merely trying to regain the kind of penetration that was normal when cutbacks were the standard for this use. Also, the solvent in the cutback will soften the asphalt in the RAP, bond it with the new asphalt in the cutback and bond the whole roadway surface together.

If you specify some kind of surface treatment, specify it must be placed within a few days of placement and compaction of the RAP - sooner the better. Once the asphalt in the RAP begins to fuse together, you won't get any penetration of your surface treatment no matter what product you spec.

 

[chicopee]

I have a solution for you however, you'll need to design your own equipment because I don't think that it is commercially available.
The asphalt milled material was laid out and compacted. After that, my company had its onwn designed, propane direct flamme heater, about 10' wide and so many feet long on wheels and towed. At certain certain rate of speed, the wheeled heating towed equipment, being fired up would softed the milled material after which it was recompacted with a roller compactor. The radiant flamme may have been about 6" off the compacted milled material.
While the finished surface may not have been the best looking work that you see on highways, it was functional on the company's properties. I seem to remember that tack coat (water base) or an oily tar product may have been used as a binder.

 

[GZ2001]

Again, many thanks to everyone for your suggestions and comments.