Cracks in new garage floor


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Old 05-04-07, 01:02 PM
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Cracks in new garage floor

Some of you may remember, earlier this year I was worried about the temperature at which a contractor may have been pouring concrete for our garage pad. The day they did it, the temp was about 30 in the morning and rose to just under 40 during the day. When they poured the pad, they did use heaters and such to keep it warm and to help it cure, but they said they had to wait around for nearly 10 hours before they said it was safely cured and left a high power halogen light on in the garage all night to keep it warm.

It is now warm, I have noticed 2 cracks forming in the concrete. One in the apron (outside where it was kept warm) and one inside that is about 5 feet long and growing. I can feel the uneven concrete along the crack, so I know it is not just on the surface. I am going to be calling them to fix it (still under warranty) but would like to have some info before I do (so I do not have the wool pulled over my eyes). So here are some questions.

Is there any sort of crack that is not major? (an excuse for them not to fix it).

Is there any situation where anything other than ripping up the old and pouring a new would be an option?

Anything else I should know before I start talking to them?

I have no doubt they will make good on their word, but I just want to make sure I have my ducks in a row before I contact them.

Thanks
 
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Old 05-04-07, 01:26 PM
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Cracks in new garage floor

How big was the slab and did you have control joints installed or sawed the next day?

Did you have 6x6 wire mesh placed in the slab? Fiber mesh in the concrete?

It sounds like shrinkage cracks.

Dick
 
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Old 05-04-07, 02:48 PM
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The slab was about 24X28, no joints were sawed (it is one continuous slab). They said they were going to use fiber mesh.

Thanks,

Dave
 
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Old 05-05-07, 03:47 AM
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24x28 is far too big for no joints. It should have been cut into four equal sections, either with a joint tool as they were finishing it, or with a saw the following day (possibly two days if it was that cold). The cracks are most likely drying shrinkage cracks.
Does your warranty cover cracks in concrete? I doubt it very much. Anyone who guarantees that concrete will not crack, especially with no joints, is either very inexperienced or somewhat less than intelligent.
Once concrete is cracked, there's no "fixing" it. That said, they could try epoxy injection to fill the cracks, but I doubt that there's anything seriously structurally wrong with your slab and guess that the cracks will not cause any problems for you in the future. I'd try to get a little money back (if the cracks are warranteed) and just live with them. I really doubt that these particular guys would know enough to be able to fix it right anyway.

Pecos
 
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Old 05-05-07, 09:18 AM
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I will check, but the contract does not say anything about excluding concrete.

How can a layman tell the difference between a shrinking crack and an actual problem crack?
 
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Old 05-05-07, 10:18 AM
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First let me say this “ALL CONCRETE CRACKS”
There are two type of cracks that affect concrete, 1) shrinkage cracks which are caused by the hydration process as the concrete sets up, these can show up as soon as the next day and 2) Stress cracks which are caused by movement of the ground below and week points in the overall design. These will usually show up after a seasonal cycle of freezing and thawing.

Shrinkage cracks RARELY travel through the entire depth of the concrete (at first)
Stress cracks DO travel through the entire depth immediately.

For instance, the reason there are joints (groves for you southern folks) every 3-5 feet in a sidewalk (depending on width) is mainly to control shrinkage cracks. If they were strictly for stress cracks one would see them every fifteen feet. Thus the term control joints, they accomplish both needs.

30 degrees is not too cold to pour flatwork if kept warm and cured properly and it sounds like your contractor did this. I suspect you have a shrinkage crack, so I question the slump of the pour. Slump= how wet the concrete was poured.

I have more information about slump here: http://h1.ripway.com/ConcreteMan/ under the chapter five, finishing.

Since it probably is a shrinkage crack I would not suggest tearing the floor out if there is proper reinforcement in the slab. It may look bad today but you do have a good floor.

Experienced concrete men understand the importance of control joints, but… it can be up to the contractors’ discretion to put them in. Village codes usually do not cover this point so you will lose in a court of law should you try to sue for this imperfection.
 
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Old 05-05-07, 11:25 AM
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I agree with concrete man except for one point. Shrinkage cracks do go the full depth of the concrete. They are not simply on the surface. Crusting cracks such as you get on a windy day can just be on the surface, but I'm sure that's not your problem.
 
 

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