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Re: Time-dependent lateral pressure on formwork

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If the concrete has hardened enough to remove the lateral pressure how do you avoid a cold joint, on a repeat pass, without serious vibration of the "set" surface, interfering with that set, and re-introducing lateral pressures?  How about designing for the full height and then run the pour, full height, with a running "active" face along the length of the wall.  I am always uncomfortable with repeat passes especially if I have no control on the length of time between passes. 
 
If the wall is so high that repeat passes are necessary, shouldn't there be allowance for a proper construction joint between lifts?

Thor A Tandy P.Eng, MCSCE
Victoria BC
Canada
e-mail: vicpeng(--nospam--at)vtcg.com
 
----- Original Message -----
Sent: Thursday, May 25, 2000 7:25 AM
Subject: Re: Time-dependent lateral pressure on formwork

One thing I was told about designing formwork for long walls is that you don't design for the pressure head of the full height of the wall. Rather you might design for a maximum of 4' pressure head. This is because when casting a long wall you do it in lifts and by the time you make
a repeated pass, the concrete has already hardened sufficiently that it is no longer applying hydrostatic pressure.