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Re: Concrete specifications

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Hi Bill:

I have a question regarding concrete strength requirement.

BOCA and UBC refer to ACI 318 for concrete strength for constructions other
than residential buildings in regard to severe exposure conditions. The
Table in the ACI 318 requires 4500 psi for concrete exposed to freezing and
thawing in a moist condition. In my interpretation, the exterior concrete
foundation wall within frost depth would be in this category for buildings
in St. Louis and Chicago area. Because the constant cycles of freezing and
thawing would put exterior concrete wall in contact with soil in moist
condition. However, the local practice in St. Louis is to use 3000 psi
concrete for all foundations in most cases. I tried to specify 4000 psi
concrete for couple of projects. But I got lots of resistance from local
contractors. I also tried to find some reference material regarding to the
ACI 318's Table. But my effort was in vain. I contacted BOCA code official
last year, they concurred with my code interpretation. However, I would
raise this question again to see if someone would have more background
information.

Thanks,

Jie Lu, P.E., S.E.
J. Lu International, LLC


-----Original Message-----
From: Bill Sherman <SHERMANWC(--nospam--at)cdm.com>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Monday, February 08, 1999 6:43 PM
Subject: Concrete specifications



I am an Associate Member of ACI Committee 301 and there is some discussion
of
how ACI codes and standard specifications are intended to be used in the
committee.  So I would like some input from other practicing engineers on
how
they use ACI documents to specify concrete:

1. Do you specify concrete by reference to ACI 301 or do you have your own
concrete specification independent of ACI 301?

2. If you reference ACI 301 from your project specifications:

a) Do you reference ACI 301 in full or only portions of it?

b) Do you also reference other standard ACI specifications (such as 306.1
for
Cold Weather Concreting, etc)? or Standard Practices (such as ACI 308 or
Curing Concrete)? or ACI "Guides" (such as 305R for Hot Weather Concreting
or
350R for Environmental Engineering Concrete Structures)?

c) Do you reference the ACI 318 Building Code from your project
specifications?

3. Have you encountered any problems with inconsistencies between ACI 301
and
another ACI code or standard specification?