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RE: Mass concrete

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Thanks for all the input. 

The pad, is a tank pad (for wine tanks).  It will be poured directly on
finish grade The design strength is 2500 psi.  

I talked to a few contractors who poured large concrete tank pad like
this in the past, and apparently no special procedures (mix design,
chilled water etc.) were taken to account for the mass of concrete.  I
have seen those tank pads, and they look good to me.

I think at this point, low cement content, maybe 4.5 sack or less should
do the trick.  Anyd suggestions?



Y i   Y a n g,   P. E.             
STRUCTURAL DIVISION
SUMMIT ENGINEERING INC.
707.527.0775.x15
Santa Rosa, California
 


-----Original Message-----
From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com] 
Sent: Wednesday, August 04, 2004 1:38 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Mass concrete


I was going to respond to this thread until I saw the name "Shilstone".
For 
the uninitiated, Shilstone is one of the true guru's of concrete mix
design.

Jay and Jim Shilstone before him probably know more about concrete mix 
design than anyone on the planet.

Thermal gradients can crack concrete quite easily.  I am not sure what
the 
function of the "pad" is, but if this is a foundation you need to ask if

this should be a concern at all.  Or can you place crack control joints
to 
accommodate cracking.  If cracking can not be tollerated, then you need
to 
take actions in mix design, placing and curing to contol the heat of 
hydration and control the thermal gradient.

I would also look to the Bureau of Reclamation.  They developed most of
the 
rules for mass concrete used today.

Regards,
Harold Sprague



>From: Jay Shilstone <j.s(--nospam--at)shilstone.com>
>Reply-To: <seaint(--nospam--at)seaint.org>
>To: <seaint(--nospam--at)seaint.org>
>Subject: Re: Mass concrete
>Date: Wed, 04 Aug 2004 14:40:04 -0500
>
>It doesn't matter whether it is called mass concrete or not. The 
>question
>is, "Is there sufficient heat differential between the interior and 
>exterior concrete temperatures to cause cracking?" If the mix involved
has 
>a high cement content, or has a high enough initial temperature, the
answer 
>is probably "Yes". When in doubt, treat it as mass concrete. You can
either 
>keep the internal concrete temperature as low as possible or insulate
the 
>whole deal to slow down heat loss.
>
>We were involved in a project with 6 foot diameter columns cast with 
>5000
>psi concrete. The concrete was cast in winter in Chicago. When the 
>contractor stripped the forms 2 days later, the concrete rapidly formed

>alligator cracks all over.
>
>If it looks like mass concrete and quacks like mass concrete, treat it 
>like
>mass concrete.
>
>Jay Shilstone
>
>At 05:15 PM 8/3/2004, you wrote:
>>I have a concrete pad, approximate 3' to 3'-6" thick, 26' wide, 100' 
>>long.
>>  Is this considered a "mass concrete"?  ACI 207 talked about the
cooling 
>>of mass concrete etc.  Most of the ACI mass concrete reports are
related 
>>to dam construction.  Is this pad "massive" enough to cause any
serious 
>>heat problem?
>>
>>Thanks for any input.
>>
>>Y i   Y a n g,   P. E.
>>STRUCTURAL DIVISION
>>SUMMIT ENGINEERING INC.
>>707.527.0775.x15
>>Santa Rosa, California
>>
>>
>
>
>
>
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