Thinking about conversion. Anyone have a ballpark rough estimate per sq. ft.? How deep does excavation have to go? Thanks
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Driveway
If you can handle the height you can pour over your existing asphalt; just cover it with an inch or so of sand. A 3.5 inch slab will do. I did my driveway a couple of years ago and poured over 50 yards for 4000+ sq. ft. The cost not including grading which I did myself came in at about $3 per sq ft. But that was based on a very good price for the mud. I had a full crew of 6 or 7 finishers at top dollar, since I was in a hurry and we were moving up hill. The first day we pumped so there was less labor. The second day required a larger crew to hand place the mud. Broom finish. If you're thinking color or texture it could be a lot more. If you have people to finish it for you at good price it could be considerably less. I'm about to do another section of driveway, which I intend to do in small sections moving down hill. I'll probably finish it myself at a considerable saving.
On part of the job I used #10 mesh, on the rest I used fibered concrete without any further reinforcing. I have only one crack and that is in the part with the mesh and seems to be caused by a whole section sliding down hill about 3/8 inch.
just cover it with an inch or so of sand
why the sand ?
planning on concrete over asphalt on a 300 ft driveway on a 10% slope, figured to pressure wash (4000 psi 4.4 GPM washer) the asphalt and punch a bunch of holes in it with backhoe teeth - 5 or 6 holes per sq ft for 'grip'.
Estimating about $1 sq ft with all own labor. Will only do 7 yards per day, tried to pour, level, and finish 18 yards once by myself 15 years ago and it about did me in then, no way I'll try more than 7/day by myself pushing 70 YO.
Gotta limit it to 7 yards anyway per truck as driver says he wont back down the drive with more that 7 yards due to tiping over backwards risk with a bigger load.
Fibered vs. mesh sounds like a good idea to save work.
You mentioned 'sliding downhill' What was your slope and what slump did you use? I was thinking a 2" slump only for the 10% grade, which makes for more difficulty leveling/finishing (broom only even) .
Sand over asphalt
The concrete guys recommended the sand. I suspect that the coefficent of thermal expansion of asphalt concrete and portland cement concrete are sufficently different that you need to provide for slipage between them to avoid cracking. 1 yard of concrete covers about 9 yards or 81 sq. ft. So depending on the cost of mud you could be at $1 - 1.50 for material.
When I mentioned sliding down hill I was talking about the concrete slab not the mud. I think a whole section moved down hill. My slope may approach 25%. It certainly does where this slippage occured.
I hope you've got at least one helper to screed with you. If you have to back the truck down hill you will be screeding mud up hill. That's what I hope to avoid. For my next stage I'll have the driver come down frontwards and pour as he goes. I've got another drive way for the truck to exit. I'll have to space each pour out over several weeks because after the first load the truck will have to drive over the finished concrete.
One advantage to the fiber is that without reinforcing you can lay your screed boards directly on the ground. I won't be pouring wider than 10' so I'll just screed from form to form. There are two kinds of fiber. One disappears and the other needs to be removed from the surface after the concrete has set. I've only used the former.
If you form up an extra 2x4 on the edges and then taper your screed board on the ends you can create a berm on the edges if you need one.
I just today passed some road construction where they're laying concrete over asphalt. Looks to be 6-8" of concrete on top of the existing asphalt roadway. What they're doing is putting down some sort of white fabric over the asphalt, before pouring the concrete.
I'd drive some rebar down to keep any sliding at bay.