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Old 05-17-2011, 11:12 AM   #1
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concrete floor

I had a concrete floor poured for my garage and cracked the next day and continues to crack. The footings are 24 wide 27 deep, base was 4" of compacked sand #4 rebar 24 oc. I could fine nothing wrong with preperation. they use large rock with fiber added. The weather was about 72 degee. I kept it damp for 5 days. The contractor wanted to cut control joints the nex day. But I didn't want them I wanted a smooth floor it was crack the next day anyway. When I showed the contractor the problem he had no explanation for the cracking and suggest he could cut some control joints in and that might help.I think something is wrong with the mix. What do you think?


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Old 05-17-2011, 11:38 AM   #2
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Were you there when they poured it?
Lots of water?
Cracked the next day!?!?
Holy Moly!!
Get pictures! (You might need them - if it's cracked already -Ouch!)


By the way - wait for the concrete experts to see this - hope they know how to use jack-hammers.


Last edited by rossfingal; 05-17-2011 at 11:43 AM.
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Old 05-17-2011, 05:41 PM   #3
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control/contraction joints should always be diamond sawed as soon as possible to prevent random cracking,,, when sawing, the current spec calls for thickness ./. 3 OR 1.3" deep if its a 4" thick floor,,, despite what you were told, fibre won't help much to control random cracking,,, i'd guess your only hope to save it now is full-depth sawing of a proper joint pattern.

why sand & not compacted fill as sand shifts ? gravel / graded aggregate base / nys dot item #4 is always recommended but never sand,,, if a 4" floor, 1 1/2" rock may be too large,,, rebar adds flexural but NOT compressive strength,,, conc likes to be square which's why we saw it,,, you shouldda listened to your contractor & let him saw,,, personally i wouldn't use fiber or wire mesh in 4" but that's often argued,,, as i recall, aci sez any steel/mesh's gotta be at the vertical midpoint +/- 5% which, in a 4" slab, is .2",,, by the time the jabonies finish tramping back& forth, guess what those odds are.

who designed this job ? your contractor SHOULD know why the cracks occurred - the joints should've been cut when the conc needed them - NOT when the owner sez,,, the next day is often too late.

Last edited by stadry; 05-17-2011 at 05:50 PM.
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