New garage floor crumbling away

Old 05-15-06, 09:16 PM
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New garage floor crumbling away

Hi, I got a garage built 2 years ago and the floor near the door is crumbling away. I think it is from the water sitting on it in the winter where it melts off the car, but doesn't dry up. I bought a garage floor mat to try to contain it, but it didn't seem to really help. What can I do? Pictures are
Old 05-16-06, 02:47 AM
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I think there are 2 different problems here. The first is that the front of the garage slab is only about 2 inches thick. It seems to have been poured over the top of the asphalt where driveway meets garage (or maybe that's concrete instead of asphalt). Either way, two inches is too thin for an area with vehicle traffic. I'd bet the concrete cracked and began crumbling there and then let moisture and perhaps salt in, starting the deterioration.
The second (very common) problem is that the door rests on the slab itself instead of the driveway. In itself, this isn't a problem. The problem occurs because interior concrete is typically not air-entrained. The concrete plant does not add air to the mix to aid in getting a slick, smooth, hard trowelled finish. Air entrained concrete should not be hard trowelled. However, exterior concrete needs air entrainment to withstand freeze/thaw cycles. Using the same mix to pour both the slab (interior) and the "weather lip" (exterior) of a garage slab is asking for trouble. I see it every day here.
Once a slab starts crumbling, there is not much to do about it. Yours is one of the worst cases I've seen. The only thing I could suggest is to saw the slab off just inside the door and break it out. Saw and break about 2 or 3 feet of the asphalt out in front of the garage too. Pour this apron back with air entrained concrete 4-6 inches thick.
Next, take a heavy duty (3000 psi minimum) power washer and blast away all loose material from the interior slab. This will need to be patched with a professional grade patching compound, being sure to follow all directions to a "T", and then sealed with a high quality sealer. This may work to stop the deterioration, but it may continue as well. The quality of the original concrete will play a part. It's possible that it would be cheaper and less time consuming to tear the whole floor out and start from scratch. Sorry! Good luck with whatever you decide. By the way, what does the contractor say about this problem? Was the floor professionally done?


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