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RE: Time Constraints on Stressing Post-Tensioned Concrete Slabs

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Not familiar enough w/ PT to comment on the maximum time, but is there enough data on the mix with early breaks (24 hr, 48 hr, or 3 day) to determine the time it takes to reach the required strength?  Another option would be to take extra cylinders for breaks at those times.  When the testing lab gets breaks w/ sufficient strength, they call you, you call the contractor and say "pull 'em."
 
Dan
-----Original Message-----
From: Jeff Creagan [mailto:jeffc(--nospam--at)kpff.com]
Sent: Wednesday, July 28, 1999 12:06 PM
To: SEAOC Listserver
Cc: John Hochwalt
Subject: Time Constraints on Stressing Post-Tensioned Concrete Slabs

Industry standard for when P/T slabs may be stressed is based on concrete strength reaching 3000 psi (or 3500).  Considering high early strength concrete, is there a guideline for the minimum amount of time before the tendons may be stressed?  Also, to prevent temporary shrinkage cracking in P/T slabs, is there a guideline for the maximum time a slab should remain unstressed?