Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: sand layer under slabs - was ACI or CRSI question-answer center

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Brian,

Unfortunately, no I do not know of any specification.

The only thing that I know of is what is in ACI 302.1R-96.  Section 4.1.5
(which has been modified by the recent flow chart) states:

"4.1.5  Vapor barrier/vapor retarder - If a vapor barrier or vapor
retarder is required due to local conditions, these products should be
places under a minimum of 4 in. of trimable, compactible, granular fill
(not sand).  A so-called "crusher run" material, usually fraded from 1 1/2
in to 2 in down to rock dust, is suitable.  Following compaction, the
surface can be choked off with a fine-grade material (Section 4.1.4) to
reduce friction between the base material and the slab.

If it is not practical to install a crusher-run material, the vapor
barrier/retarded should be covered with at least 3 in of fine-graded
material, such as crusher fines or manufactured sand (section 4.1.4).  The
granular fill, as well as the fine-graded material, should have sufficient
moisture content to be compactible, but still be dry enough at the time of
concrete placement to act as a "blotter" (section 4.1).

If a vapor barrier/retarder is to be placed over a rough granular fill..."

HTH,

Scott
Ypsilanti, MI


On Tue, 5 Nov 2002, Brian Spencer wrote:

> Scott,
>
> Do you or anyone know what ASTM or DOT number to use for
> the "blotter" material?  We are trying to find a specification
> for this material.
>
> Thanks
>
> Brian Spencer
> Tylk Gustafson Reckers Wilson Andrews, LLC
> 407 South Dearborn, Suite 900
> Chicago, IL 60605
> bspencer(--nospam--at)tgrwa.com
> http://www.tgrwa.com
>
>
> >
> >Ken,
> >
> >First of all, the most current recommendation on the "blotter" layer (if I
> >recall correctly) was to use a layer of "crushed fines" or something
> >similar.  The idea was to have a layer of something that would allow the
> >moisture from the bottom side of the slab to migrate into that layer
> >allowing the slab to cure.  Initially, the recommendation was sand (which
> >allows movement of moisture relatively well).  The problem with sand is
> >that it gets "mushed" during construction (i.e. placement of rebar,
> >placement of concrete, etc) which can destroy the nice uniform surface.
> >Thus, the idea of using something like a well-draining crushed fines that
> >can compact relatively well and not be distrubed during the rest of the
> >construction process.
> >
> >The recent change has been with the use of the "blotter" layer with a
> >vapor barrier.  Recent information indicates that this formerly
> >recommended system (a "blotter" layer under the slab but on top of the
> >vapor barrier) can create problems with some moisture susceptible flooring
> >materials.  The problem arrises from the fact that any moisture that gets
> >trapped between the vapor barrier and the bottom of the slab in the
> >"blotter" layer (i.e. rains after placement of the vapor barrier and the
> >"blotter" layer but before the placement of the slab and not enough time
> >is allowed for the "blotter" layer to dry; "excessive" moist cure that
> >causes moisture to get in to this layer; wetting of the "blotter"
> >layer prior to placement of concrete...a common/required practice; etc)
> >can only go in one direction...up through the slab.  The potential result
> >is that the moisture/vapor emmision rate could be high enough to cause
> >some flooring materials to fail.
> >
> >The result is that ACI 302 and 360 issued a revised flow chart for
> >determining when to use vapor barriers and what other conditions should be
> >required with or without the vapor barrier.  This was issued in the spring
> >of 2001 in an issue of Concrete Construction.  Additionally, the revision
> >should be included with any new purchases of the main ACI 302 or 360
> >documents and likely the MCP.  This subject was discussed on the list a
> >couple of months ago...take a look at the archive.
> >
> >HTH,
> >
> >Scott
> >Ypsilanti, MI
> >
> >
> >On Tue, 5 Nov 2002, Ken Peoples wrote:
> >
> >> Is this true?  Is the sand layer no longer recommended?
> >>
> >> Kenneth S. Peoples, P. E.
> >> Lehigh Valley Technical Associates
> >> 1584 Weaversville Road
> >> Northampton, PA 18067-9039
> >> Phone: (610) 262-6345
> >> Fax: (610) 262-8188
> >> e-mail: kpeoples(--nospam--at)lvta.net
> >>
> >> ----- Original Message -----
> >> From: "Roger Davis" <rdavis(--nospam--at)sdsarch.com>
> >> To: <seaint(--nospam--at)seaint.org>
> >> Sent: Tuesday, November 05, 2002 8:06 AM
> >> Subject: RE: ACI or CRSI question-answer center
> >>
> >>
> >> > Scott,
> >> > That warm fuzzy feeling is what I wanted.  Questions seldom
> >come up until
> >> > you need an answer.  I want immediate feedback so I can
> >continue with the
> >> > work that brought up the question.  The answers that you and others
> >> > contribute on this list have confirmed some of my opinions and made me
> >> > change my mind on some things and educated me on many others -
> >they seldom
> >> > come with any authority like a ruling from an ACI committee  but that
> >> > doesn't bother me. I judge for myself whether or not to accept
> >them - just
> >> > like I did with the old ACI Committee recommendation to place
> >a sand lift
> >> > under a concrete slab on grade. I think it was only appropriate under
> >> > special circumstances even though the committee recommended it
> >for years
> >> > until they recently reversed themselves.
> >> >
> >> > Roger C. Davis
> >> > Architect
> >> > SDS Architects, Inc.
> >> >
> >> > -----Original Message-----
> >> > From: Scott Maxwell [SMTP:smaxwell(--nospam--at)engin.umich.edu]
> >> > Sent: Monday, November 04, 2002 5:05 PM
> >> > To: seaint(--nospam--at)seaint.org
> >> > Subject: RE: ACI or CRSI question-answer center
> >> >
> >> > To clarify what Jay wrote below...
> >> >
> >> > What he states is absolutely correct if you want an "official"
> >> > interpretation of something in an ACI document.
> >> >
> >> > On the other hands, if you want the opinion of an INDIVIDUAL who was
> >> > involved with the creation of that document, then members of
> >committee's
> >> > can give their own opinion.  The key is that it is the opinion
> >of that one
> >> > individual, NOT an official opinion in any way.  It may be
> >that opinion is
> >> > correct and co-insides with what the official interpretation
> >would be if
> >> > rendered.  The end result is that getting the opinion from an
> >individual
> >> > committee member or an ACI staff member (or staff member from
> >CRSI, PCA,
> >> > PCI, etc) may give you a warm fuzzy feeling, but it is more or
> >less worth
> >> > what you paid for it (i.e. nothing) if you want to use it in
> >any form of a
> >> > legal or substantive arguement.
> >> >
> >> > So, to use Roger's example, the answer he got was only useful
> >to give him
> >> > a warm fuzzy feeling.  Even though it came from a member of the 318
> >> > committee, it was not in anyway an official answer or a
> >respresentation of
> >> > what was actually meant other than that individual's opinion.
> >> >
> >> > FYI, ACI staff member when they do respond to technical inquiries will
> >> > sometimes contact committee members to see if one is willing to get an
> >> > opinion.  Not only does this potentially get a more
> >authoritative (notice
> >> > the adj.) for the person asking the question, it can also
> >point out to the
> >> > committee where there are some items of confusion that may need
> >> > clarification in the next iteration of the document.
> >> >
> >> > HTH,
> >> >
> >> > Scott
> >> > Ypsilanti, MI
> >> >
> >> >
> >> >
> >> > ******* ****** ******* ******** ******* ******* ******* ***
> >> > *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> >> > *
> >> > *   This email was sent to you via Structural Engineers
> >> > *   Association of Southern California (SEAOSC) server. To
> >> > *   subscribe (no fee) or UnSubscribe, please go to:
> >> > *
> >> > *   http://www.seaint.org/sealist1.asp
> >> > *
> >> > *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> >> > *   send to the list is public domain and may be re-posted
> >> > *   without your permission. Make sure you visit our web
> >> > *   site at: http://www.seaint.org
> >> > ******* ****** ****** ****** ******* ****** ****** ********
> >> >
> >>
> >>
> >> ******* ****** ******* ******** ******* ******* ******* ***
> >> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> >> *
> >> *   This email was sent to you via Structural Engineers
> >> *   Association of Southern California (SEAOSC) server. To
> >> *   subscribe (no fee) or UnSubscribe, please go to:
> >> *
> >> *   http://www.seaint.org/sealist1.asp
> >> *
> >> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> >> *   send to the list is public domain and may be re-posted
> >> *   without your permission. Make sure you visit our web
> >> *   site at: http://www.seaint.org
> >> ******* ****** ****** ****** ******* ****** ****** ********
> >>
> >
> >
> >******* ****** ******* ******** ******* ******* ******* ***
> >*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> >*
> >*   This email was sent to you via Structural Engineers
> >*   Association of Southern California (SEAOSC) server. To
> >*   subscribe (no fee) or UnSubscribe, please go to:
> >*
> >*   http://www.seaint.org/sealist1.asp
> >*
> >*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> >*   send to the list is public domain and may be re-posted
> >*   without your permission. Make sure you visit our web
> >*   site at: http://www.seaint.org
> >******* ****** ****** ****** ******* ****** ****** ********
> >
> >
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   without your permission. Make sure you visit our web
> *   site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********
>


******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ********