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RE: SLAB - Control Joints in Concrete Slab on Grade

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I believe that you have been very lucky with the use of Fibermesh. If you
review the product literature, I believe you will find that the company does
not recommend the use of Fibermesh as a replacement for reinforcement or
even WWF to control temperature cracking. I had a contractor substitute the
additive for WWF in some small tract homes that I designed. In residential
construction, the care and quality during the curing process of concrete is
very poor. Each of the slabs cracked considerably in the first three weeks -
more from the fact that the slab was allowed to sun dry while it was curing
and no care was given to keep it moist.
Fibermesh is suppose to be used in commercial and industrial slabs to reduce
temperature cracking in slabs with appropriate reinforcement - not as an
alternative to. You can argue that on residential projects not designed to
Federal lending conditions, there is not code requirement for either welded
wire fabric or reinforcing - except for continuous steel in the perimeter
foundation or slab edge.
I would caution any engineer who is led to believe that Fibermesh is a
replacement to temperature steel - I have met some very disappointed
homeowners and contractors who had to spend the money on Epoxy injection to
correct the conditions.
That's my $0.02 worth.

Dennis S. Wish PE


-----Original Message-----
From: Bramhall [mailto:mab(--nospam--at)nwlink.com]
Sent: Saturday, April 25, 1998 5:58 AM
To: seaoc(--nospam--at)seaoc.org
Subject: Re: SLAB - Control Joints in Concrete Slab on Grade


I have used Fibermesh in slabs-on-grade in lieu of wwf for two or
three projects for the same owner.  I think it works quite well
but great care must be taken in the early stages of the slab to
ensure excess shrinkage does not occur.  If Fibermesh (or an approved
equal) is to be used in lieu of steel reinforcing, ALL parties
involved (owner, architect, SE, contractor, testing agency, etc.)
need to be keenly aware of the unique advantages and shortcomings of
fiberous reinforcing.

The deletion of the wwf in these projects was a result of a value
engineer process for the first project and became the "standard" for
the subsequent projects.  The slabs under the office buildings
turned out very well but very large random cracks appeared in slabs
under the fre standing parking garages.  The cause of this cracking
was due to the fact that the slabs in the garage were exposed to the
elements (direct sunlight, warm temperatures and breeze) while the
slabs under the buildings were protected (formwork and basement
walls) as soon after being finished.  Once the cracks in the garage
slabs had reached a certain width the Fibermesh was of no use and no
backup method remained to distribute the shrinkage throughout the
slab.  We ended up epoxy injecting some of the smaller cracks and
replacing a few other sections (20'x20').


Michael Bramhall, PE