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Re: S.O.G.

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Andrew,

I am like Harold...I like to specify rebar in slab-on-grades (and on metal
deck).  Usually either #3 or #4 at about 18 inches (allows more of a
chance that the workers might beable to step between the bars leaving the
reinforcement more likely to be where it is supposed to be).

This is a lesson from first boss out of school.  He did not like WWF.  The
issue of it coming in rolls and not being able to be straightened out was
pat of it.  His real beef with WWF, however, was that he did not enjoy the
entertainment of seeing construction workers out in the field trying to
lift themselves, eh, the WWF into place with hooked bars.  As a result, we
tended to spec rebar.  If WWF was to be permitted, it had to be in flat
sheets and what he referred to as "big foot" type (heavier gage/diameter
wires at larger spacing which in theory deform less when walked on and
possibly could allow for steping in the spaces).

We also on occasion would use steel fibers.  He like Harold was not a fan
at all of poly fibers.  He reffered to them as "peach fuzz" (on a side
note, a Gail pointed out I believe, poly fibers CAN be effective...just
not in the volume content that is typically recommended/used in SOGs...for
poly fibers [and PVA, glass, etc) to be useful, you typically need a high
enough volume content that makes the concrete REALLY tough to work
with...in fact, if I recall correctly, it becomes more effective if done
with a REALLY high volume content of fibers that are placed in the forms
prior to placement of the concrete and then a slurry mix of concrete is
used (i.e. REALLLY low slump with no larger aggregate)...commonly reffered
to as SIFCON, at least in my experience).

HTH,

Scott
Ypsilanti, MI


On Fri, 18 Jul 2003, Andrew Kester wrote:

> Thanks to Harold and Scott for their great advice on slabs on grade.
>
> As Scott said, the ACI does address the base material between the vapor
> retarder and the slab. This is a good read- ACI 4.1.5, but see the Addendum
> at the end of the Chapter, 302.1R-96, Vapor Retarder Location, and the
> accompanying flow chart. This has been a real eye opener and I hope to
> reevaluate the way we design and specify SOG. It is very dependent on the
> expected/known finish floor material...
>
> I guess it is a bit simpler on exterior slabs where you do not need a vapor
> retarder.
>
> Harold, you said to use rebar in SOG, so are you using #3, about 1.5" or 1/3
> from the top of the slab? And since it is agreed that even this won't
> prevent cracking, however, it should hold the widths to acceptable limits.
> And do you design the reinforcement ACI 360R-21, EQ (6-3) and the thickness
> according to one of the methods listed in Chapter 5 (PCA, WRI, or COE
> methods)??
>
> Thanks again for all of the input.
>
> Andrew Kester, EI
> Longwood, FL
>
>
>
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