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RE: Spec needed for 3000 psi concrete

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Ghias,
In this case, there are three separate pours; 1) the erection pads for the
columns; 2)the grade beam to tie the columns together; 3) the finished slab
above. 
The finished slab is expected to float over the grade beam, but we will
probably put a control joint at the inside edge where the grade beam and
earth meet. The floor finish at this area is carpet so the issues related to
cracking is not severe - as I wrote in a previous post, the need to control
the standards for the concrete appears to be much more important due to the
weakness of the supplier working for the General Contractor.

Dennis


Dennis S. Wish, PE


California Professional Engineer

Structural Engineering Consultant

dennis.wish(--nospam--at)verizon.net

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-----Original Message-----
From: Ghias Dean [mailto:GDEAN(--nospam--at)dot.state.tx.us] 
Sent: Monday, October 11, 2004 5:47 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Spec needed for 3000 psi concrete

It is not a good idea to increase the cement even though you will get
higher strength but if you are not careful in placement techniques you
will get lot more floor cracking than with 5 sack concrete.

Ghias Dean PE
Austin Texas

>>> sscholl2(--nospam--at)juno.com 10/8/2004 7:24:05 PM >>>
Why use "3000 psi" concrete which then requires a Deputy inspector at
a
cost of about $75/hr? 
Instead specify 5.5 or 6 sack mix, limit the water and you will end up
with about 4000 psi but won't have to pay for the inspector.

This is especially important for smaller jobs.

Stan Scholl, P.E.
Laguna Beach, CA

On Fri, 8 Oct 2004 11:57:05 -0600 "David Maynard"
<davemaynard(--nospam--at)ceincorp.com> writes:
Dennis,

I tend to agree with Joe on this one.  Really let your contractor do
the
work.  The more guidance you give him, the more liability you accept
on
the project.  Typically for our concrete specs, we call out the
following
things:
1. Portland Cement type and ASTM spec.
2. Fly Ash type, content, and applicable ASTM spec.
3. 28-day Compressive Strength
4. Max. Course Aggregate
5. Max. Water/Cement Ratio
6. Air Content
7. Slump

Based on this information, you contractor should be able to come up
with
the proper mix design.  Anything more, and you start obtaining
liability.
 I hope that helps.

Dave Maynard, PE
Consolidated Engineers, Inc.
Gillette, Wyoming

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