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Re: time before building on or backfilling concrete foundation walls

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Desi,

Very true.  But keep in mind that all the ACI documents that you mentioned
are NOT code documents.  They are (very good) recommendations, but have
no "force" other than standard of care.  I was mainly addressing the
question of whether or not ACI 318 (the structural concrete code)
addresses the issue...and it does not.  It largely does not addresses the
issue because the issue of when to strip forms, backfill, etc. is really a
case by case decision.  75% of the 28 compressive strength will likey work
in most cases, but there can be cases when the full 28 day compressive
strength maybe required depending on what construction loads are expected.
Thus, it is not really possible (or advisable) to place such a requirement
in the code since in some cases the requirement could not be sufficient.

HTH,

Scott
Ypsilanti, MI 


On Fri, 16 Aug 2002, desi j kiss wrote:

> 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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