Expansion gaps in concrete driveway


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Old 11-14-06, 02:37 PM
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Question Expansion gaps in concrete driveway

I have a concrete driveway that has several thin cracks across it. It's my opinion that they occurred because there are not enough expansion gaps. I'm considering adding some additional expansion gaps across the concrete, but I have a few questions:
1) How many feet apart should the expansion gaps be? The driveway is 11 feet wide.
2) I've read that an expanion gap is just 1 inch deep. Is this right? I thought it had to go all the way down to the ground.
3) How wide should the gaps be? The ones already in my driveway look like about 1/2 inch.

Thanks for your input.
 
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Old 11-14-06, 06:29 PM
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Expansion gaps in concrete driveway

You should not be concerned with "expansion" gaps. Your concern should be with control joints that control where the concrete cracks as it shrinks during the curing process. these are usually installed prior to or during the concrete placement. The preferred method is you saw them after the concrete is placed.

The general guideline is for them to be 1/3 of the depth of the slab. This provideds a weakened plane wher the concrete will crack. After sawing, the joint should be filled with a good caulk to seal the joint and prevent dirt from filling the joint.

Wire mesh is usually used to minimize cracks and fibre mesh mixed into thr wet concrete may also help if you do not have properly spaced joints.

If you already have cracks, it is because the concrete has already cured and has shrunk, forming the cracks. If the slab is over a month old, additional joints would have no effect.

You could fill the existing cracks to allow them to move and prevent them from filling with debris.

I would suggest you contact the person that planned and poured your slab.

Dick
 
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Old 11-15-06, 07:16 AM
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three know facts about concrete: 1. it cracks.
2. it gets hard.
3. noone will steal it.
 
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Old 11-15-06, 03:19 PM
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Concretemasonry:

My driveway is 20 years old. So, based on your statement "If the slab is over a month old, additional joints would have no effect." , there's no point in adding additional joints now.

Thanks for the info.
 
 

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