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RE: [CONCRETE] When Is Concrete "Cracked"?

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As others have pointed out, it kind of depends on the use of the concrete element.  In many ways, size and spacing of cracking is typically more of a servicibility issue or aesethic issue than a strength issue.  Generally speaking in strength terms, it matters little whether the crack is 1/1000 th of inch thick or 1/2 inch thick (this is not completely true as a wider crack could potentially lead to bending/shearing of the bar in addition to tension, which could cause "issues...but is when you get REAL extreme with crack widths).  It is concerns about corrosion and other protection issues and users freaking out that will generally be more of the issue.  Thus, it becomes much more subjective and also a function of use (i.e. a crack in a bridge member that is exposed to moist, salt laden air is MUCH different than a crack in a beam inside a building that has a controlled humidity and "normal" air and both are much different than a crack in a tank).
 
It is also a function of what type of cracks are they...flexural tension cracks, shear cracks, radial tension cracks from compression, etc. and where they are on what type of element.  Just mentioning a crack does not really tell us much.
 
Regards,
 
Scott
Adrian, MI
-----Original Message-----
From: bill(--nospam--at)polhemus.cc [mailto:bill(--nospam--at)polhemus.cc]
Sent: Friday, May 16, 2008 2:42 PM
To: seaint(--nospam--at)seaint.org
Subject: [CONCRETE] When Is Concrete "Cracked"?

I know that reinforced concrete "always cracks," but what is the criterion for determining when it is "too cracked;" that is, that the cracks are significant enough to need attention?

Seriously, I've had a tough time finding a defnition of this in ACI documents, etc.