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RE: Cylinder Breaks vs. Mix Design

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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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