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#1
Old 04-23-2002, 09:08 AM
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Concrete driveway - rebar or wire mesh?

Wondering if any of you could help me evaluate bids on our Chicago-area residential driveway. We have it narrowed down to 2 contractors. They are about $1G apart, with the higher bid approx $8G to install a concrete driveway in our home.

The higher bidder proposes installing 1/2" rebar. The lower proposes using wire mesh combined with fiber added to the mix.

The higher bidder says wire mesh does nothing to reinforce the concrete, it only holds the concrete together once it starts to crack. The lower bidder says the rebar is overkill. Moreover he says it is hard to install properly for a 5" thick floating slab, and could actually cause problems.

Both propose using sealant. We do not use salt, and intend to do our best to keep salt off it for the first couple of winters.

Both have great references, and impress us with their professionalism.

I know nothing about concrete. All I know is that I don't want to pay for a brand new concrete drive, and have it look like crap in a year or two.

It wouldn't break our bank to go with the higher bid, but I hate to think I would be just pissing away a thousand dollars. This is such a frustrating thing, trying to make a decision about a product I really know nothing about.

Any thoughts?
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#2
Old 04-23-2002, 09:24 AM
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I would opt for the rebar. The mesh is probably sufficient if you don't have a lot of shrinking and expansion, however for something you drive on every day, I wouldn't risk it. If it was a small patio or something, then the rebar would be overkill. Then again, when I do something involving construction, I usually do things overkill, so the mesh could be sufficient, but I would not be comfortable with it. However, have you thought about pricing a blacktop driveway, or is there a reason you want concrete?
#3
Old 04-23-2002, 09:34 AM
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Wife really wants concrete. So do any other reasons matter?

In her opinion, concrete looks "dressier", the color will lighten up the whole front of the house, it is "cleaner" in terms of the kids playing on it and stuff. Maybe she has other reasons, but suffice it to say she has a strong preference for concrete and we can fit it into the budget, so I'm not going to try to convince her otherwise just to save a few bucks and have her resenting it forever after.

We had a concrete drive put in at our previous house, and I was very disappointed when 1 year later it pitted and flaked considerably. I understand it was from road salt dripping off our car when we parked it right outside our door - say for hauling in groceries - instead of pulling into the detached garage. I was very disappointing to spend extra $ on what you hoped would be a superior product, which you would think would outlast you, and have it look so bad so soon.

One thing that makes me think of going with the rebar is, as that guy says, you don't want to risk anyting going wrong with a concrete drive, because you can't correct it. Can't patch it as blacktop.
#4
Old 04-23-2002, 11:15 AM
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If you have a really big driveway, rebar is preferable. But I can't tell just what size it is. They just put one in next
door with rebar, its about a 30 foot by 17 foot area.
#5
Old 04-23-2002, 11:20 AM
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This probably doesn't help...

There are a couple of reasons for each option, but I don't know how to evaluate the answers:

Structural Integrity
a) rebar gives more structural integrity to the slab, since a few thousand pounds are going to be sitting in very small portions of the driveway (tires). I don't know whether the strength of the concrete is enough to withstand the regular pinpointed pressure.
b) the fiber may be enough to hold the concrete together given the outside forces...like hair in old plaster.

Climatic changes
a) the wire mesh will likely cause less stress on the concrete during the cold snaps that occur in the Chicago area. I doubt the rebar would distress the concrete in the first couple of years, but suspect that it could cause problems later on.
b) the fiber would be less prone to this sort of change and keep the smaller cracks from appearing.

Design may be the most important. I would think that ensuring that the water always has somewhere to run off would have the biggest impact to maintaining the quality of the slab. Puddles sitting on it are going to be bad.

The sealant is probably a good idea to save it from salt but also from oil/gas/road grime that may cause premature wear.

Check references from each and see the condition of their previous work. They'll give you their success stories, but you may be able to evaluate them acurately anyway.
#6
Old 04-23-2002, 11:54 AM
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Re: This probably doesn't help...

Quote:
Originally posted by cantara
Check references from each and see the condition of their previous work. They'll give you their success stories, but you may be able to evaluate them acurately anyway.
Yeah - everyone we have contacted sings their praises.

Of course, the only guarantees they offer are against fire and theft!

What do you mean about the possible stress caused by rebar in response to weather over time?

I think the driveway is around 1400 sq. ft. - 2 cars wide, approx 40' long, with a good-sized turnaround area.
#7
Old 04-23-2002, 02:24 PM
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Rats, my first reply disappeared... here it goes again.

My husband works for a company that makes wire mesh and stranded wire for prestressed concrete. I asked him what kind of reinforcement he'd use for a driveway as you described. He said mesh with fiber reinforcement for these reasons:
  • 1. The mesh is welded, providing stability along 2 axes. Rebar is tied together to form the pattern (labor intensive, hence more expensive)
    2. The fiber in the concrete is especially advantageous in extremes of temperature.
    3. Structurally, concrete in mesh acts like a series of blocks, making it more flexible under stress - I didn't entirely understand this, but he wouldn't lie to me...
He did say that when it's poured, it's important that the mesh be in the center of the thickness of the slab. There are little spacers that hold it off the ground and while it's being poured, they should periodically lift the mesh so it's surrounded by concrete.

FWIW, this is how he intends to have our driveway done when we build our house in Maryland. Hope this helps.
#8
Old 04-23-2002, 02:30 PM
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How was the concrete slab built at your previous house? Mesh or rebar? How long did you have it? Was there any cracking?

I think just as important as the concrete will be the make-up and compaction of the base material that the slab sits on. Bad or poorly-compacted material will heave or shrink, creating voids under the slab. This will allow the concrete to crack and heave. Since both of your contractors come highly recommended, I'd guess this won't be a problem for you.

Another advantage of concrete is that you can add pigment and texture. A contractor can even press rubber stamps into the surface of wet concrete to make it look like tile or flagstones (if he has the right equipment, of course). Pretty cool when done right, and it's probably not too expensive an option to add.

The pattern can even hide any future cracks, because the low points in the pattern (between the "stones", so to speak) will act as stress relievers, like the seams in a concrete sidewalk.

Have you considered either of these things?
#9
Old 04-23-2002, 02:39 PM
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Concrete slabs crack. Concrete slabs really crack in Chicago. Nothing will prevent this. What you want is to keep the cracks from spreading and the surface from becoming uneven. Wire mesh does this better.
#10
Old 04-23-2002, 02:41 PM
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Re: Re: This probably doesn't help...

Quote:
Originally posted by Dinsdale
Of course, the only guarantees they offer are against fire and theft!
Do people often steal driveways or set them on fire in your neighboorhood?!? That would worry me more than the rebar vs. mesh question!
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#11
Old 04-23-2002, 03:05 PM
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I had some new sidewalks poured a few years back. There is one section where it makes a 90 degree corner. It cracked at this corner after two years. It probably should have been poured in two sections with a joint at this point.

I'd guess that if your drive is poured in small sections, with expansion joints in between, the cracking might be confined to these joints.
#12
Old 04-23-2002, 04:50 PM
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The Journal of Light Construction did an article on this a while back (I'd link, but they charge for their online stuff now.) In that article, a rep for a company who makes fiber reinforcement was quoted as saying that fiber reinforcement was meant for reducing cracks as the concrete cures; it isn't meant as a structural reinforcement.

BTW, this was discussed here (more or less) before.

Admittedly, I live in the South and have only heard of snow, but my vote is for rebar on one-foot centers max.--those big bars will not rust and pull apart like wire does. Expansion joints will control where the concrete cracks.

Then again, rebar v. wire may be a moot point. Some people build residential slabs without any reinforcement (I wouldn't!) I've also heard of people successfully building driveways with really stiff concrete and no rebar (one-inch slump, but I think most concrete guys would rather go to jail than work a 1" slump mix.)
#13
Old 04-23-2002, 06:47 PM
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Suggestion

Keep in mind there are different gauges (thicknesses) and sizes of wire mesh. Here's my supplier, Ivy Steel's website.

You didn't state the size of your driveway or thick you were going to pour. But $8,000 sounds like a huge driveway.

Before you sign a contract, why not look into a concrete pavingstone driveway. Here's some pictures from my local suppliers, Nicolock and Anchor. You must have at least 6 manufacturers in your area to choose from. They are asthetically MUCH nicer than concrete, you have a huge choice when it comes to color and shape, oil dripped pavers are easy to replace, they're durable, they come tumbled or untumbled and only run $2.00 [/] retail and $3-6 [/] for installation.
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#14
Old 04-23-2002, 07:34 PM
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One more thing hubby asked me to mention - factory floors never have rebar in them - it's always mesh... these are heavily loaded applications. He also said your best bet would be a monolithic pour, tho that could be a tad pricier.
#15
Old 04-25-2002, 11:19 AM
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The quality of the cement is the most important question. Ask the bidders what the pound rating is, and take the higher one. I suspect the fiberous cement will contain a higher cement mix, and therefore come out with a higher rating.

The Germans are the ones who first came up with the fiberous cement, and if anyone knows their cement, it's the germans.
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