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When should cables be pulled on above ground PT slabs?

When should cables be pulled on above ground PT slabs?

When should cables be pulled on above ground PT slabs?

(OP)
Is there a recommended or required waiting period?

RE: When should cables be pulled on above ground PT slabs?

When the concrete is strong enough to withstand the tensioning stresses.

RE: When should cables be pulled on above ground PT slabs?

Typically when the concrete has reached 70-75% f'c.

RE: When should cables be pulled on above ground PT slabs?

They should be tensioned progressively.  If you wait too long, too much early age restraint cracking will result.  Usually start when site cylinders get to about 15 MPa, but that can vary.  Check with the PT contractor for recommended times for the given system.   

RE: When should cables be pulled on above ground PT slabs?

min compressive strength of the concrete at time of stressing = 4 ksi for multi strand and 2.5 ksi for single.  As for the time restraint, I am not aware of any other than practical considerations.

Of course, the contractor must prove the strength of the concrete with cylinders prior to stressing.

RE: When should cables be pulled on above ground PT slabs?

We require the tensioning of elevated slabs/beams to be complete within 96 hours of the pour.  It's up to the contractor to make sure he gets a mix that can reach your required stressing f'c early enough to complete the operation within the window alotted.

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