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RE: Time Constraints on Stressing Post-Tensioned Concrete Slabs

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In large slabs in hot weather, I typically specify a partial stress (50% of design stress) within 24 hours of the original pour, provided the concrete has attained 2000 psi compressive strength.  PTI indicates maximum time to full stress shall be 10 days; however, I prefer 7.
 
Brian K. Smith, P.E.
Louisiana
-----Original Message-----
From: Jeff Creagan [mailto:jeffc(--nospam--at)kpff.com]
Sent: Wednesday, July 28, 1999 11:06 AM
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?