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Concrete crack control

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     Jeff,
     
     In addition to looking at ACI 350 I would also recommend you review 
     ACI 224R-90, "Control of Cracking in Concrete Structures".  If you are 
     looking for a text book reference I would recommend "Reinforced 
     Concrete Structures" by Park and Paulay (chapter 10.4 in my version).
     
     Thomas Hunt, S.E.
     Fluor Daniel


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Subject: Concrete crack control
Author:  "Jeff Smith" <smthengr(--nospam--at)sirius.com> at fdinet
Date:    12/11/98 5:44 PM


Can anyone suggest a good reference for concrete crack control in exposed 
concrete walls. Are there any rules of thumb for crack control as a function 
of strength, w/c ratio, type of aggregate, type of forms, spacing and size of 
control joints, etc.
     
We just finished a 20 foot section of 11' tall, 10" wall, double curtain 
reinf,  that will not be exposed, but was used as a mock up for a future 
pour.
     
We had a .43 w/c ratio, 3/4 aggregate, 5500 psi mix with poly fibers, using 
mahogany forms on one side and ac ply on the backfill side. The finish looks 
like it was steel troweled, glassy smooth. However, there are two 8' long 
vertical hairline cracks that occur between snap ties about 4-6' apart. The 
crack does not extend to the back side of the wall.
     
The 4.1 Point Richmond quake was a few days after the pour, I can't believe 
that was what caused it. We already completed an orthogonal wall that was 
about 40' long that was board formed, no control joints, using pea gravel 
that has no cracks in it. 17 day compression test was 4300 psi.
     
Thanks,
     
Jeff Smith