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RE: ACI 318-05 minimum slab on grade reinforcement spacing

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Geotechnical reports, in my opinion, should not be used as a guideline for minimum reinforcement and spacing requirements.
I would recommend that you not exceed the Code maximum of 18-inches on center and I would also recommend that you not use anything less than a #5 bar. #4 and particularly #3 bars are very susceptible to damage just due to foot traffic before and during the slab pour.
Lastly, I would highly recommend that, if there are any senior engineers in your office, that you don't be shy and ask for their input. Senior engineers are usually more than willing to share with the new guys how they like to do things.
Matthew Stuart


From: Jeff Hedman [mailto:jeff(--nospam--at)]
Sent: Mon 1/22/2007 6:59 PM
To: seaint(--nospam--at)
Subject: ACI 318-05 minimum slab on grade reinforcement spacing

I have been searching through the code for minimum slab on grade spacing.  It appears that according to ACI 318-05 7.6.5 and limit the maximum reinforcing spacing to 18" o.c.  Is there no way around this for a slab on grade?  It doesn't appear so but I have seen plenty of other plans as well as geotechnical reports that state #3 bars @ 24" o.c. or #4 bars @ 24" o.c. to be used.  Neither meets the 18" o.c. requirement and for the #3 bars to meet the 0.0018 reinforcement ratio the #3 bars should be spaced at 15" o.c.

Jeff Hedman , E.I.T.


L.R. Pope Engineers & Surveyors, Inc.

1240 East 100 South Suite # 15B

St. George, Utah  84790

Office: 435-628-1676

Fax: 435-628-1788

email: jeff(--nospam--at) <mailto:jeff(--nospam--at)> 


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