Need a book? Engineering books recommendations...

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

RE: Mass concrete

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I would suggest the following:
1.  Allow some flyash replacement of the cement
2. Be generous with the rebar to conrol the cracks, and use rebar in the top and bottom
3.  Use as large a maximum nominal aggregate as possible
4. Require a minimum of 8% and no more than 18% on all the C33 sieves below the nominal maximum (wisdom from Shilstone)
5.  Use polycarboxilate super plasticizer
6. Put plastic sheets and insulation blankets on the surface to minimize thermal gradient. (This may be an overkill, but I would at least use the plastic sheets and wet it down for curing)

Jay Shilstone's opinion trumps any of my humble suggestions.

Harold Sprague

From: "Yi Yang" <YI(--nospam--at)>
Reply-To: <seaint(--nospam--at)>
To: <seaint(--nospam--at)>
Subject: RE: Mass concrete
Date: Wed, 4 Aug 2004 14:32:27 -0700

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.
Santa Rosa, California

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

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

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
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
accommodate cracking.  If cracking can not be tollerated, then you need
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
rules for mass concrete used today.

Harold Sprague

>From: Jay Shilstone <j.s(--nospam--at)>
>Reply-To: <seaint(--nospam--at)>
>To: <seaint(--nospam--at)>
>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
>is, "Is there sufficient heat differential between the interior and
>exterior concrete temperatures to cause cracking?" If the mix involved
>a high cement content, or has a high enough initial temperature, the
>is probably "Yes". When in doubt, treat it as mass concrete. You can
>keep the internal concrete temperature as low as possible or insulate
>whole deal to slow down heat loss.
>We were involved in a project with 6 foot diameter columns cast with
>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
>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'
>>  Is this considered a "mass concrete"?  ACI 207 talked about the
>>of mass concrete etc.  Most of the ACI mass concrete reports are
>>to dam construction.  Is this pad "massive" enough to cause any
>>heat problem?
>>Thanks for any input.
>>Y i   Y a n g,   P. E.
>>Santa Rosa, California

Is your PC infected? Get a FREE online computer virus scan from McAfee® Security.

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at:
* * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to:
* Questions to seaint-ad(--nospam--at) 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: ******* ****** ****** ****** ******* ****** ****** ********