Subgrade preparation

[decolores9]

For a new concrete apron, adjacent to an existing concrete driveway, which option would you prefer, and why?

1. Place concrete directly on (well compacted) soil.

2. Place concrete on 2" of 1B pea gravel

3. Place concrete on 4" of 1B pea gravel

4. Place concrete on 2" of 2B gravel

5. Place concrete on 4" of 2B gravel

6. Place concrete on 2" of 1B and 2" of 2B gravel (2B on top)

7. Something else.

Are there any inherent advantages of 2B over 1B, or vice versa? I used one triax of 1B to fill the interior garage foundation and plumbing pipes, now I need a second triax, and am debating whether to get 2B instead.

Thanks.

[Rich]

I don't know about 2A, 2B or the like. If this will have large equipment or trailers on it my personal recommendation would be to overexcavate a foot. Fill with 3-5" rip-rap or similar. It won't compact much but more drives it into the existing grade. Then fill with any compactable fill up to the final sub-grade and compact it to 95% or better.
If it's just going to bear normal vehicles then you could probably get away with using any compactable fill - dirt compacted to 95+%.

[RobBase]

For a residential driveway; well compacted subgrade free of "roots, grass, mud, etc. with 4" of anykind of gravel, but preferably 3/4" crushed stone that has had a plate tamper run over the top of it. Gravel is gravel unless your 1B/2B is some type of crusher run that has fines in it.

What's a triax?

[Tom R]

I second that, what's a triax?

[Rich]

Enlighten me too. I would imagine it's some type of earth hauling truck.. maybe dealing with the configuration of the trailer - a belly dump maybe??

[mjpliv]

Tri - axle maybe???? Just a guess. Probably just a 20 ton dumptruck.