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Re: 50' oc control joints for SOG ok?

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I would add one cautionary note about saw cutting.  In order to be of any use, it needs to be performed within about 3 to 8 hours of setting (depending on ambient temperature conditions).  I have often seen the concrete poured in the morning, finished by early afternoon, then saw cut the next day, then they wonder where all the cracks came from (...."but we put the joints in just like the engineered showed on the drawings....").

Thomas Hunt, S.E.
ABS Consulting




"S. Gordin" <mailbox(--nospam--at)sgeconsulting.com>

08/16/2005 09:25 PM

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Re: 50' oc control joints for SOG ok?





Scott,
 
ACI 302.1, Page 10:  "For under-reinforced, plain concrete slabs [contraction/saw-cut] joint spacing of 24 to 36 times the slab thickness, up to a maximum spacing of 18 feet have produced acceptable results. Some random cracking should be expected."  
 
ACI 302.1, Page 11: "The aspect ratio of slab panels that are unreinforced [or] reinforced for shrinkage only... should be a maximum of 1.5 to 1; however, a ratio of 1 to 1 is preferred."  
 
For 6-inch slab I would recommend saw-cut 3/16"x1" joints at 10-ft (12-ft maximum) square pattern.
 
Steve Gordin, SE
Irvine CA
 
 ----- Original Message -----
From: Bill Polhemus
To: seaint(--nospam--at)seaint.org
Sent: Tuesday, August 16, 2005 5:11 PM
Subject: RE: 50' oc control joints for SOG ok?

> I agree it does seem much. If the floor cracks up the calcs are worthless
> though.

What a way to find out.


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