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RE: Cylinder Breaks vs. Mix Design

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Randal,

I will add to Robert's comments that I don't believe I have ever received a
correct concrete mix submittal on the first try.  ACI 301 Section 4
provides all the details of what the supplier should submit and I would
insist on getting it.  Once you get the proper information then I would
scour it with a fine tooth comb.  I just received several mix designs this
year with aggregate gradations out of spec among other things.  Get a copy
of ASTM C33 and verify the course and fine aggregate gradations.  Verify
the correct cement type which is probably called out in your soils report
as either Type I, II, or V.  Calc out the water/cementitious ratio and
check the proposed air content to insure it matches your exposure
conditions.  Slump is very important and in general (assuming nothing
special) should be 4 inches.  I just had a submittal with a proposed slump
of 1 to 2 inches (yikes!! how do you even get it out of the truck without
adding water!?!).  If additives are being proposed check the vendor data
sheet for typical dosage rates.  It is easy to read 6 oz. instead of 0.6
oz.  This may seem silly but check the proposed strength on the mix design
sheet.  I just had a 4000 psi submittal when we requested 5000 psi.  Check
where the water is coming from.  If the water is coming out of a river or a
well then I would have it tested.  I once had some bad concrete due to
contaminated river water and well water can become very brackish (i.e. full
of salts).

Good Luck,

Thomas Hunt, S.E.
Duke/Fluor Daniel

----- Forwarded by Tom Hunt/DFD on 03/27/02 07:13 AM -----

                    "Rogers,
                    Robert"              To:     <seaint(--nospam--at)seaint.org>
                    <rogersr@amkin       cc:
                    ney.com>             Subject:     RE: Cylinder Breaks vs. Mix Design

                    03/27/02 05:45
                    AM
                    Please respond
                    to seaint






Randal,

This is one of the most misapplied processes in our industry (in my
opinion).  ACI 318 is very clear (including a flowchart) of what is
required for submittal as a concrete mix design.  When using compressive
strength test data:

1) First, the supplier must have enough test data to establish a standard
deviation for the mix design or assume one from a table in the code.  This
means that the mix design required average strength is always higher than
the specified strength.
2) Second, the supplier must show that the average from many strength tests
acquired from pours exceeds the required averaged strength (established by
testing and statistical evaluation of a standard deviation).

If sufficient test data is not available, trial mix design (i.e.,
laboratory mixes) are done & tested to establish the required average
compressive strength (always higher than the specified strength).  The code
allows an option to approve a mix design without either of these, however,
its use is only applicable in certain situations (see ACI 318-99, 5.4).

Hope this helps....

Robert



Robert C. Rogers, PE
Senior Structural Engineer
A.M. Kinney, Inc.
Consulting Engineers / Architects
150 East Fourth Street, 6th Floor
Cincinnati, Ohio 45202
PH: 513-421-2265, ext. 125
FX: 513-345-1318
rogersr(--nospam--at)amkinney.com
www.amkinney.com


     -----Original Message-----
     From: Randy Diviney [mailto:rsdiviney(--nospam--at)hayeslarge.com]
     Sent: Wednesday, March 27, 2002 8:35 AM
     To: seaint(--nospam--at)seaint.org
     Subject: Cylinder Breaks vs. Mix Design



     I have a quick question on review of concrete submissions.





     Should I be concerned with the concrete mix design submittals if the
     cylinder breaks are satisfactory? If so , what should I look out for?






     TIA








     Randal S. Diviney P.E.


     Director of Structural Engineering


     Hayes Large Architects


     (814)946-0451


     ******





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