The concrete cover requirements and minimum thickness of elements (such as
slabs or walls) listed in the UBC or any other code are "catch alls".
Concrete cover requirements for interior conditions are typically controlled
by fire rating rquirements. One can reduce the cover or thickness if
substantiated by analysis. I have done this before for slabs and beams, but
never for walls. Reference ACI 216R-81. This is included in the ACI Manual
of Concrete Practice 1990 Part 3. With only 1/4" of cover, I don't know if
you could make it calc. out.
There are paints available for steel that provide fire rating. I have used
these before on steel structures, not concrete. They are very expensive. I
don't remember the brand name.
From: Javier Encinas [mailto:jencinas(--nospam--at)coqui.net]
Sent: Thursday, June 08, 2000 3:21 PM
Subject: Concrete cover
During the construction of a concrete wall in a building the reinforcing
steel was misplaced in such a way that the rebars were located too close to
the forms, which resulted in a cover of about 1/4".
The owner of the building has contracted our services to perform an
assessment of the concrete wall and provide some possible solutions other
than demolishing the wall. I am considering some sort of solution consisting
on epoxy-painted surface and cement plaster to improve the steel protection.
Has anybody used any commercial product or procedure in a similar situation?