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RE: Concrete specifications

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I am not sure which table you are looking at, but I think you are looking at
Table 4.2.2 in ACI 318-95.  If that is the case the minimum concrete
strengths are only applicable to lightweight aggregate concretes.

Also, damp proofing is the common practice on subgrade walls and they will
be protected from moisture exposure.

Regards,
Harold Sprague
The Neenan Company
harold.sprague(--nospam--at)neenan.com


-----Original Message-----
From: Jie Lu, P.E., S.E. [mailto:jayjielu(--nospam--at)worldinter.net]
Sent: Tuesday, February 09, 1999 5:09 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Concrete specifications


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