Stripping Times[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "SEAOC" <seaint(--nospam--at)seaint.org>
- Subject: Stripping Times
- From: "Raul Labbé" <rlabbe(--nospam--at)ctcinternet.cl>
- Date: Sat, 30 Mar 2002 12:40:52 -0600
I would like some opinions regarding the timing for stripping forms
and props in RC structures, when using special, early strength concrete.
The code states these times, for normal conditions and pending on the
span and the ratio ( self weight / total final load ). More than once we have
had the question from contractors to diminish this timing, with the use
of some special cements, or additives ( accelerators ) reaching higher
strength in early days.
What I know, is that diminishing the stripping times may result in premature
capilar cracking, which is hardly ( if not impossible ) to repair later.
Right now we are facing the following case : an RC industrial building with
one story frame structure and the main heavy equipment ( Turbogenerator )
supported at the same level but in an independent structure ( big slab-pad,
4.5' thick, spanning 5 and 7 mts. between columns ). According to ACI
( ACI code number . . . I don't have it right now at home ), we stated
14 days for stripping the building frames, which have not more than 5 mts.span
and a low self weight, and 21 days for the Turbogenerator pad.
In order to rush-up the works ( which are already late ), the contractor is
raising the special cement solution ( I've not seen, as yet, specifically which one )
declaring that with this, he can improve the timing in some 10 days !
Regardless an early high strength, a lower bound is to be used, which ?
Thanks, in advance, for your opinions.
Raúl Labbé SE.
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