I suppose someone should complicate this discussion by pointing out that not all fiber reinforcement is glass fiber. We have used synthetic fibers in base coat stucco mixes for years with good results in terms of both crack resistance and durability.
Proper dispersion of the fibers is imperative, as "balled up" fibers can create air pockets that take in moisture. The same thing happens when you add too much. In the factory this is easy to control, though.
Mike E

Sent via BlackBerry from T-Mobile

From: "Hammarberg, Eric" <[log in to unmask]>
Date: Tue, 18 Aug 2009 08:09:28 -0400
To: <[log in to unmask]>
Subject: Re: [BP] Basement floor

I have not done much concrete in the past 10 years or so... I have always been concerned about the glass fibers drawing water into the concrete and then having freeze thaw problems. Does this happen?
I thought this is one of the reasons for spraying a rich slurry mix as the outer layer in GFRC.
Thanks,

Eric Hammarberg, Assoc. AIA
Vice President
Thornton Tomasetti
51 Madison Avenue
New York, NY  10010
T 917.661.7800  F 917.661.7801
D 917.661.8160
[log in to unmask]
www.ThorntonTomasetti.com

This message was sent from my PDA, please excuse misspellings or similar mistakes.


----- Original Message -----
From: The listserv where the buildings do the talking <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Mon Aug 17 22:16:43 2009
Subject: Re: [BP] Basement floor

One thing that has changed how concrete is reinforced is called "fiber".
It's actually fiberglass strands about 1" long which are added to the dry
mix and work amazing well to control cracking. The only minor downside is
the fact that power troweling lifts the fibers out of the surface so the
slab can get a bit fuzzy, but that wears off quickly after the cure with
foot or vehicle traffic.

I have found that adding fiber to the mix when capping a chimney is a huge
advantage in controlling cracks.

Supposed to be the wood guy,

Rudy

-----Original Message-----
From: The listserv where the buildings do the talking
[mailto:[log in to unmask]] On Behalf Of Larry Simpson
Sent: Tuesday, August 18, 2009 7:36 AM
To: [log in to unmask]
Subject: Re: [BP] Basement floor

I've never seen rebar in a basement floor although wire mesh was sometimes
used in the past. Rebar is no longer used in curbs or sidewalks in Ohio
because, the non coated stuff tends to rust out and cause more damage where
salt water from road de-icer seeps through cracks. Green bar (epoxy coated)
is used extensively in structures but is not considered cost effective for
non structural pours. 5000 psi concrete is adequate for properly prepared
concrete pours on graded ground.

Larry2
Public Works Inspector
Cincinnati, Ohio

 ---- Lawrence Kestenbaum <[log in to unmask]> wrote:
> Okay, so the contractor showed up this morning, and they have been
> jackhammering the basement floor to open up a 2' wide trench along the
> outside walls.  Last I looked, they were more than half done
> trenching.
>
> From the concrete chunks they have been dumping in their truck, the
> concrete floor is about five inches thick.  But, to my astonishment,
> it's just concrete, no rebar.
>
> How would a concrete basement floor stay nice and flat for 50+ years
> without any reinforcement?  Don't they use rebar even in sidewalks?
>
>                     Signed, Never Actually Poured Any Concrete Myself,
> Just Helped Install Forms, And That Was More Than Three Decades Ago in
> Arizona
>
> ---
> Lawrence Kestenbaum, [log in to unmask]
> Washtenaw County Clerk & Register of Deeds, http://ewashtenaw.org
> The Political Graveyard, http://politicalgraveyard.com
> P.O. Box 2563, Ann Arbor, MI 48106
>
> --
> To terminate puerile preservation prattling among pals and the
> uncoffee-ed, or to change your settings, go to:
> <http://listserv.icors.org/archives/bullamanka-pinheads.html>

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