Correct Concrete Driveway Construction


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Old 11-14-09, 01:56 PM
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Correct Concrete Driveway Construction

My driveway is 16' wide and 50' long and I am having a spirited debate w/ the concrete contractor over these items.

1. Turning down the concrete at the perimeter and whether rebar is needed

2. If fiberglass resin is added, do I also need the reinforcing wire mesh

3. If I opt to have a row of vertical accent bricks in lieu of the expansion joints, should they be the heavier paver bricks or masonry bricks

Thanks!
 
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Old 11-14-09, 02:21 PM
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1) Driveways are typically not turned down on the perimeter. They are 4 inches thick throughout. Maybe 6 inches if you drive heavy trucks (not pickups) or have a motor home.
2) It's not fiberglass resin, it is strands of polyethylene or nylon fibers added into the mix. They are added in lieu of wire mesh. However, it wouldn't hurt to have both. If you do, however, expect to pay extra for it. Usually it's one or the other. I personally use fiber and some rebar in the concrete to hold it together when it does crack...which it WILL! Expect cracks, but hopefully in the joints and not randomly throughout the slab. Rebar is not typical around here, but I do it anyway. Expect to pay extra for that as well.
3) Paver bricks would hold up much better than masonry bricks. Don't mortar them in or the mortar will deteriorate with freezing and thawing.
Keep in mind that a 16 foot wide by 50 foot driveway should have a joint down the center lengthways, and evenly spaced joints crossways. The sections created by these joints (they're actually called crack control joints, not expansion joints) should be roughly square. To be effective, the joints need to be at least 1/4 as deep as the concrete is thick. For example a 4 inch thick slab should have joints at least 1 inch deep; a 6 inch slab...1.5 inches deep, etc.
Good luck with your driveway.
 
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Old 11-14-09, 06:41 PM
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P,

It sounds like you know concrete.

So, you think turnig down the concrete is overkill, but the steel reinforcing with the fiber mix is worthwhile?

The old 25 y/o driveway had expansion joints with some fibrous material that has deteriorated, but I believe went the full depth of the concrete, as mud and sand come up when you hit the joint with water.

I will ask about a vertical control joint that runs the length of the driveway also.

Should sand be used to tie the paver bricks together?

Thanks!

RoseRx
 
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Old 11-15-09, 05:17 AM
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Did the 25 year old driveway have any cracks in it? Perhaps one that originated somewhere around the middle of the slab lengthwise? If so, that's a dead giveaway that there should have been a center joint. 16 feet in any direction is too far between joints; they shouldn't be farther apart than 10 feet on a 4 inch thick slab. A 16 foot drive definitely needs one up the middle.
The black fibrous stuff is expansion joint material. It will certainly deteriorate over time. They make different kinds now that won't deteriorate, including rolled foam expansion that I use. There are also some made of hard rubber.
The turned down perimeter whould serve no purpose, unless you are constantly driving heavy trucks or equipment off the edge of the driveway and onto the soft ground next to it. Even then, benefit would be minimal.
Most of the cracks you see in concrete happen within days after the pour. They are shrinkage cracks, caused by the stresses associated with the concrete losing it's water during hydration. That's why you place crack control joints; to make the concrete crack there instead of randomly.
The fibers are intended for two things: to stop cracking, and to hold the slab together if it does crack. The manufacturers say that when a crack starts on a microscopic level, it will intersect a strand of fiber and stop. This sounds good in theory but I'm not really sold on that. I use fiber because it is easier to use than mesh, and it is dispersed throughout the entire matrix instead of just in one plane like wire mesh. Not to mention that if mesh gets stepped on while pouring, it just sits on the bottom where it does no good. Fiber is everywhere. I add the rebar to hold the different cracked pieces on the same plane so there is no differential settling between different sections of concrete.
Install the paver bricks according to the manufacturer's instructions. That's not my thing. I pour stamped concrete that resembles brick instead, so it's all part of the same slab with no loose pieces.
 
 

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