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RE: 50' oc control joints for SOG ok?

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I suggest you consider the function of the slab and whether you can tolerate cracks in the slab.  As we all know, concrete will crack somewhere.  If you can tolerate cracks in the slab and you want to rely on the SF method then go ahead.  But if you can’t tolerate them then put them in much more frequently.  Also, rebar placement plays a big part in crack control.  If the bars don’t make it up to the top then you will get much more cracking.  I recently did a 6 inch slab with joints at 25 ft. on center in one direction and about 15 ft. in the other.  It cracked at about 12.5 ft. in just about every panel.  The owner had serious concerns.  I didn’t know of their crack concerns until after the concrete was poured.  Had I known before I would have put joints in more frequently than I did.

 

Personally, I don’t trust the SF method.  I always get much higher spacing than the rule of thumb of 2-3 times slab thickness.  From my experience, in the real world the rule of thumb holds up much more than the SF method.

 

Rich

 

 


From: Haan, Scott M POA [mailto:Scott.M.Haan(--nospam--at)poa02.usace.army.mil]
Sent: Tuesday, August 16, 2005 4:04 PM
To: seaint(--nospam--at)seaint.org
Subject: 50' oc control joints for SOG ok?

 

 

For a 6” slab on grade is it acceptable to have a 50’ oc control joint spacing for no. 4 @ 18” oc ea way.  I am looking at a tensile stress based on subgrade friction formula that calculates out.

 

Thanks.