Graded Base vs. straight stone Dust on roadway/driveways

[paulharvey]

I thick putting fines on top of the existing base is asking for trouble. If you don't scarify the original base you won't get any bonding, and the top will either "scab" or will get washed off. I would rip the whole problem area, add material of your choosing (here in Florida we use mostly a soft crushed limerock with between 40-60% rock and the rest is lime and small remains of the crushing process).

I personally like asphalt millings because they don't wash, and compact well into a solid base. But they can be expensive (limerock is $6/ton picked up, and millings(RAP) can run as high as $20/ton) if you don't have a good source of them.

 

[Red Horse]

Where I live now and where I grew up most of what was in the pits was/is granite. My Dad and brother put in a driveway of just stone dust a foot deep that held up very well for 20 years (it was paved over after that). If your traprock is similar to granite, I could see just dust working well for a "top dress" over the existing base. It would be easy to spread, and as long as you kept at least a slight crown I don't think water would be a big problem...?

Foot deep? for sure it would hold up well

 

[Red Horse]

I thick putting fines on top of the existing base is asking for trouble. If you don't scarify the original base you won't get any bonding, and the top will either "scab" or will get washed off. I would rip the whole problem area, add material of your choosing (here in Florida we use mostly a soft crushed limerock with between 40-60% rock and the rest is lime and small remains of the crushing process).

I personally like asphalt millings because they don't wash, and compact well into a solid base. But they can be expensive (limerock is $6/ton picked up, and millings(RAP) can run as high as $20/ton) if you don't have a good source of them.

PH- I hear you on the "scab". Not an issue here as I have hit the base in some areas with a heavy 7 shank box blade-existing stone base was probably 6" thick- or an 8 ' Land Pride Power rake-one with the parallel hardened ribs on the rollers not the nubs like Harley's have.

Agree with you on millings. I did my own driveway (500') with millings two years ago. Used the LandPride power rake and borrowed a 60" vib roller (rubber drive wheels). Has held up very well through two winters-in particular this last one that saw a lot of snow. Largest nearby quarry used to sell it at a decent price. Last year, they stopped selling straight RAP and started selling a blend of 1/3 RAP, 1/3 crushed concrete, and 1/3 shingles. Great stuff to work with but doesnot bond the way straight RAP does. One thing that I think led up to this "new product" is MA DOT increased allowable percentage of RAP in new asphalt.

Also, some "environmentally sensitive" people have issues with RAP as a stand alone finished product. I guess when its asphalt on a roadway, the runoff is okay- when its RAP-"oh my-hazardous run-off":confused2:

 

[BuilderML]

The material you elect to use will depend on the amount you are adding. Here is what i like to use.
1' of material added= i use 3" minus top with 3" of 3/4" minus
4"-12" of material added= use 1 1/4"-1 1/2" minus
under 4" of material added= use 3/4" minus

When using to large of material with to little of an amount is what creates a rough job.
Hope this helps.
I would not us just stone dust that will only wash away.
Have fun