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Re: time before building on or backfilling concrete foundation walls

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Scott,

The engineer should specify the min. strength ot the concrete to be
attained before removal
of forms or shores.   Determination of the time of form removal should be
based on the resulting
 effect on concrete ( see ACI 305R and ACI 306R).     When forms are
removed before the specified 
curing is completed, measures must be taken to continue the curing and
provide thermal protection
for the concrete.
ACI COMMITEE REPORT 347R-14  provides an EXCELLENT guide to formwork and
removal of forms
and supports for concrete.     Paragraph 3.7.2.3 should provide the
answer to the question posted.

Hope this helps.

Desi J. Kiss, M.S., P.E.



On Fri, 16 Aug 2002 01:41:27 -0400 (EDT) Scott Maxwell
<smaxwell(--nospam--at)engin.umich.edu> writes:
> Gerard,
> 
> I don't believe that ACI 318 has anything on this.  I looked through
> quickly to be "sure" and did not find anything.
> 
> Scott,
> 
> This would typically be a judgement call by the engineer of record 
> (kind
> of ironic considering the other thread out there about judgement 
> <grin>).
> Gerard's answer is consistant with what I have seen/used in the 
> past.  I
> am used to specifying that the concrete must obtain 75% of the 28 
> day
> strength, which will typically occur fairly close to the 7 day 
> point.
> 
> HTH,
> 
> Scott
> Ypsilanti, MI
> 
> 
> On Thu, 15 Aug 2002, Gerard Madden, PE wrote:
> 
> > Scott,
> > 
> > Typically it is 7 days after casting unless high-early strength 
> concrete
> > is utilized. Compressive strength is about 65% of 28 day strength 
> (if I
> > remember from concrete class-10 years ago) at 7 days. This should 
> be a
> > typical note in the general notes of any project. Not sure if this 
> is in
> > the code, but ACI may have it in their ACU 318.
> > 
> > -gerard
> > 
> > -----Original Message-----
> > From: Haan, Scott M. [mailto:HaanSM(--nospam--at)ci.anchorage.ak.us] 
> > Sent: Thursday, August 15, 2002 4:18 PM
> > To: Seaint list (E-mail)
> > Subject: time before building on or backfilling concrete 
> foundation
> > walls
> > 
> > Are there any rules of thumb about time limits on when it is 
> acceptable
> > to
> > start building on a concrete foundation walls and footings?  It 
> seems
> > you
> > would not want to backfill a basement wall or retaining wall until 
> the
> > design strength is reached but I cannot find a code reference and
> > wondered
> > if there is any guidance published on the subject.  
> > 
> > Thanks.
> > 
> > Scott M Haan P.E.
> > Plan Review Engineer
> > Building Safety Division 
> > Development Services Department
> > Municipality of Anchorage
> > http://www.muni.org/building
> > phone:907-343-8183  
> > fax:907-249-7399
> > mailto:haansm(--nospam--at)ci.anchorage.ak.us
> > 
> > 
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