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JAL

Concrete question for car port

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Question or two for the concrete guys... plan on having concrete poured under a car port (shed roof off pole building) to park the car and pick-up. How thick should I plan, and what concrete mix (3500, 4000 psi, or?).

 

Other thing, my father-in-law (the know all Sussex Co DE type) swears fiber mesh in concrete provides the same strength as pouring a slab over wire mesh. Others I've talked to, say the fiber mesh is helps prevent the surface cracking, but wire is worth the added cost for a strong slab, especially one to park cars on. That makes the most sense to me... so what's the scoop?

 

I was planning a 5" slab poured over wire mesh, thinking 3500 psi mix, and to use the fiber mesh. Over kill, not enough, any recommendations... still in the planning stage this time. Want to do it once RIGHT.

 

Thanks,

JAL

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I had a slab poured for parking a few years back. Twenty four years as a matter of fact. The concrete guy I used p[oured the slab thicker in the center and tapered out to approx 6" ay the sides. So it turned out to be 10 inches at the center. Made for a strong crack free slab. It ws poured over wire mesh.

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Two cars? Minimum 5". Use wire for sure. The glass mesh does help for surface cracks, provided you cure it correctly. 4000 PSI absolutely.

Be sure to pull the wire up into the center of the 'crete as you pour it. Too many times I've seen cracked slabs with wire laying on the bottom doing nothing but rusting away. If you get a concrete hoe, you'll see a hook kinda thingy on the other side from the blade. This is for grabbing the wire and pulling it up into the center of the pour.

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Definitely use wire. I think your FIL was talking about short strand fiberglass being incorporated in the concrete, not fiberglass mesh. Two completely different things. Fiber concrete is increasing in popularity due to its ability to resist surface cracking.

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Thanks,

 

I always heard the fiber help prevent surface cracks, not providing the structural strength of wire.

 

So I should be OK with minimum 5" slab of 4,000 psi, poured over wire mesh...

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Yeah. Sounds like you're good to go. 4000 psi might be overkill for your project. 3000 psi will do the job. Check prices. If there is little difference in price go high psi. Short load (<10yds) and weekend OT prices will affect cost per yard. It's all relative. Don't forget to consolidate the concrete as you place. And as BL said, make sure you pull up the wire into the center strata of the slab as the concrete is placed, otherwise it will not function as intended. Have fun and make sure you have a bud or two to help and have all your finishing tools handy and ready to go with a good source of water (hose/buckets) nearby. beers.gif

And (as my my engineering mind/terms OCD kicks in) cwm31.gif concrete is placed not poured. If it's poured it has too much water in the mix and won't meet specification. Properly PLACED concrete takes more work to Place it where you want it and have it cure up to spec. Just my $.02 biggrin.gif

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Last question, would it be wise to lay poly down before I lay the wire mesh? Since this is a open car port (just a shed roof, not an enlosed or heated garage), I doubt a vapor barrier is needed, but does Poly help control the cure rate of the concrete... heard various opinions on this.

 

Thanks for the tips. I'm just doing the grunt work- prep work and help rake & screed it out. Have someone experienced to float and finish it for me since I don't want to 'learn' on a job this size.

 

Just wanted to make sure I was on the right track on the slab to park vehicles on...

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I would not bother with plastic. Mainly good as a vapor barrier under a house or basement slab. Cure rate won't be affected either way unless you put plastic OVER the fresh concrete. That would slow down curing.

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View PostAnd (as my my engineering mind/terms OCD kicks in) cwm31.gif concrete is placed not poured. If it's poured it has too much water in the mix and won't meet specification. Properly PLACED concrete takes more work to Place it where you want it and have it cure up to spec. Just my $.02 biggrin.gif

 

 

Not true with todays superplasitcizers. True, you don't want to move it around any more than necesary, so proper placing is good, but it's just a slab, and with a front discharge mixer, that's easy.

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View PostPutting Visqueen or another plastic sheet on top of the concrete will trap moisture and help prevent shrinkage cracks.

 

 

 

Or simply run a sprinkler on it keeping it damp for a week. Keeping it damp for several days will help with proper full hydration and curing.

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