Adding a drive

[Arcticdude]

I'm looking at finishing out the rest of my drive for my birdhouse. Here's my dilemma:

The original drive was done with 6" 3500psi concrete and 3/8" rebar on 24" OC. It cracked the first time I drove over it (this was AFTER it had cured for at least 30d). It now has numerous cracks in it and has been driven over about 30 times total.

So in considering the new drive, I want to avoid that cracking. I fully understand that some cracking is inevitable, especially with the spongy soil I've got, but the parking slab is subjected to MUCH more long term weight and only has a few cracks in it, all of which are due to soil, not bus weight.

I'm being told that wire mesh will help avoid the cracking, but not finding much corroborating evidence to back up that claim online.

So do I stick with the rebar or try the wire mesh? The drive will not normally have anything parked on it and the heaviest thing driving across it will be the bird.

[patticake]

Try rebar or wire mesh that is used on interstates. Usually you have specify that grade of wire.

[Bob Johannesen]

I would suggest over engineering it this time. I did mine with 6 " thick 5000 psi and used #3 rebar (3/8") on 6 inch centers, where the bird would NOT sit or drive. I used #5 (5/8") on 6 inch centers where the bird would drive and sit. My footings around the edge are 12 inches wide by 18 inches deep loaded with rebar. I wanted to be able to jack it up while sittiing in the barn.
Have fun and good luck![/u]

[davidbrady]

I'd stick with rebar and I'd add lots of it like Bob suggested (on 6" centers). Use high tensile rebar (60,000psi), and place it 2" from the bottom of the slab, so if you have a 6" slab you'd have 2" of concrete, then rebar, then 4" of concrete. When the slab bends it's the rebar that goes into tension adding tons of strength. The top concrete goes into compression, also adding tons of strength, the bottom concrete beneath the rebar is there for show. :-) (actually it's there to protect the rebar and to transfer loads into it, but it does nothing for the flexural strength of the beam. Add soft cut's to control shrinkage cracking, (10' x 10' grid).

If you use wire mesh you need to calculate the cross section area and make sure you have enough. If you're using #5 rebar like Bob suggests then make sure the wire mesh has the same amount of steel in it; i.e., say you have #5 on 6" centers then for every 6" depth of concrete you have (pi*.098=0.31 sq in of steel) cross section area of rebar. Do the math with screen mesh and see if you get 0.31 sq inch in every 6" depth. (measure the wire diameter, take the cross section area, and add up the number of wires in a 6" depth).

Simplified Engineering for Architects and Builders, Ambrose, J. TripenyTripthy, 10th edition, John Wiley &HobokenHoboken, New Jersey.

[pairodice]

Wow, this is all getting to sound very expensive... What about the fibered concrete like used on runways? Is it way more expensive?

[encantotom]

there is lots of discussion on this topic at the garagejournal forum. have a look over there.

tom

[neontwister]

I am getting a slab poured along with a new back driveway. I have been lurking and reading. I am going with 30 yards of 5000 psi concrete , 6 inches thick with a 12 inch footer around the edge and a big rebar, I think they said 5/8ths on 6 inch centers. Its 18, 45 pad with a 30 foot 10' wide driveway. I wanted a real steel building but the county said I had to have lap siding and the local steel company said they don't do that. I am getting a Carolina Carport finished on all four sides , insulated with a 10 / 14 roll up door. They say it meets all Florida wind ratings and has state mastered plans. I have to wait on the plans as every garage is a little different. Waiting on FDOT to okay the new culvert and then its fly time. This concrete guy is pushing. I like that. I got a tree stump already dug up and a pile of dirt as big as a car out there. Hopefully FDOT is a go tomorrow and I can pull permits, or Monday. Worse case I shift it a little west to the center of the yard. Will send pics soon.


So far so good. Didn't help my county had its servers hacked. They were down for a week. Now another week before I can form and pour.

[Arcticdude]

Sounds like a good start! I hope it all goes off with minimal hitches.

[neontwister]

Forms are in. Rebar is in. Umpteenth inspection between 4 different permits are done. 30 yards of 6500 PSI (I was wrong in my earlier comment) are coming tomorrow. I'll be sitting in my car out in the street late into the night to keep the cats, dogs and kids off my wet concrete. By Friday I will have the carport permit applied for. That should be in by the end of November. Making headway gentleman.

On the coach front. We went to the WOG rally in Pine Mountain last week. It was our first long trip with the coach. I drove 12.5 hours and 500 miles each way non stop. Not doing that again. Really screwed me up for a few days. I'm not 60, but far from 25 so sitting that seat like that is a no go I found out. Coach drove like a champ. Need some new shocks but that is about it. The fuel tank sender acted up the first two tanks. Got down to a half, shot up full and stayed there. The third time I tanked , it worked right. Guess not getting any action for a year might have froze it up or something. Seems better now. With Winter coming, plan is to update a ton of stuff on the coach. Thanks again to those who helped me. More news ASAP.

[Arcticdude]

Sounds like it's coming together well! As far as the drive, that's got to be pretty normal. You're certainly going to be more stressed driving the bird for a few more trips. Then that 500 mile day won't be any issue. Obviously, it's nice when you don't have to drive 500 miles in any given day, but knowing you can if needed will make it easier.