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Re: Slab Cracks

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ASLCSE(--nospam--at)aol.com wrote:
> 
> Dear fellow engineers:
> 
> I am looking for a book or guidelines regarding cracks in slabs-on-grade
> (mainly in residental construction).
> How else do you explain to a lay person, after she or he removed the carpet
> and finds cracks (hairline to 1/16") in the slabs (no vertical off-sets, no
> signs of of differential settlement or settlement) that these cracks are
> shrinkage cracks (high water content ehen paced and/or little or no curing)
> and that some may have gotten bigger due to the earthquake and aftershocks.
The Portland Cement Association publication "Slabs on Ground" 
recommends control joints in slabs spaced in feet at 2 to 2.5 times the
slab's thickness in inches.  For a 4 " slab you should have control
joints at 8 to 10 foot on center if you want to "control cracks".  The
problem is that for residential slabs, cracks are not controlled because
there is no need to if covered with carpet and control joints cost
$$$$$$.  The standard of care is to place it and let it crack and then
cover it with carpet.  In kitchens and bathrooms, with vinyl or tile
floors, more strict measures-like reinforcing steel- to control vertical
offesets is needed.  
norm
-- 
Norman Brudigam C.E.

Bay Engineers Inc.	Specializing in the Evaluation
(510) 284-3300x20	and Repair of Existing Structures
FAX   284-3365
Primary Email: norm(--nospam--at)bayengineers.com
Secondary Email:  nbrudigam(--nospam--at)aol.com