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RE: Fibermesh Topping Slab

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Tim,

 

Your observation is a good one.  I have seen many products that performed very well in the laboratory to only fail miserably in the field.  The Sarabond example I pointed out led to millions of dollars in law suits.  It did very well in the lab.  It performed miserably in the field, but only after about 5 years or so.  The result was thousands of projects being constructed that were doomed to failure.  There were several lawyers and a couple of testing labs in Chicago that got very rich due to Sarabond.  At one time, HUD specified Sarabond in their specifications. 

Regards,
Harold O. Sprague

-----Original Message-----
From: Tim Allison [mailto:AllisoT(--nospam--at)trusjoist.com]
Sent:
Friday, October 03, 2003 9:22 AM
To:
seaint(--nospam--at)seaint.org
Subject: RE: Fibermesh Topping Slab

 

While my hands-on experience with this is limited to laboratories, my impression is that steel "dogbone" fibers are most effective when used WITH polypropylene fibers?  The mix and placement required care to disperse the fibers adequately, but the synthetic fibers did well resisting the small cracks from developing while the steel fibers did well in resisting the larger cracks and providing some strength in tensioned areas.

>>> spragueho(--nospam--at)bv.com
10/03/03 10:04AM >>>

Thomas,

 

I have done the steel fiber deal, too.  They perform very well.  The only down side is the potential for balling in the truck.  But if you can get them dispersed in the mix, they perform very well.  But that is a big if. 

 

I would never use polypropylene fibers for anything except to reduce rebound in shotcrete, but you have to use them at 15 pounds per cubic yard or more in that application.  And even then, I would prefer steel fibers.

 

The biggest lesson is to look at all vendors with a suspicious eye.  I normally require a test placement with new concrete products.  But you only find the problems with something like polypropylene fibers when you do a full scale placement.  And then it is too late.  On the plus side, polypropylene fibers create almost as much work for lawyers and repair specialists as did Sarabond.  Good news for lawyers is bad news for engineers.

Regards,
Harold O. Sprague

-----Original Message-----
From: THunt(--nospam--at)absconsulting.com [mailto:THunt(--nospam--at)absconsulting.com]
Sent:
Thursday, October 02, 2003 6:03 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Fibermesh Topping Slab

 


Brian,

Fibermesh (the brand name) is made from synthetic fibers, typically polypropylene and as you have seen generally gets bad press.  You may want to research metal fibers which under certain circumstances may be used in lieu of WWF temperature steel.  I do not have personal experience with this but have seen some interesting studies and of course some good old industry hype.

Thomas Hunt, S.E.
ABS Consulting

 



"Brian K. Smith" <smithegr(--nospam--at)bellsouth.net>

10/02/2003 10:02 AM

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Fibermesh Topping Slab

 

 

 




We recently completed the design of a 3 story assisted living center
Construction is pre-cast hollow core with cmu walls.  We specified a 2"
composite topping slab with welded wire fabric.  One of the contractor's VE
options was substitution of fibermesh for the WWF in the topping slab.  Is
this common????  The shear loads are relatively low due to the depth of the
structure and the spacing of the interior walls, but this just seems like a
bad location to use fibermesh.  Any thoughts or experience???  The structure
is in south
Florida, high wind but no seismic.


Brian K. Smith