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Fibers in Concrete

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I would like to get some different opinions on using Polypropelene vs. Nylon
fibers in concrete slabs-on-grade.

Some facts:

Fibermesh typically recommends 1.5 #/yd and Nycon recommends 1 #/yd. I have
heard of some engineers using as much as 3 #/yd since they say 1.5 #/yd is
not enough to control plastic shrinkage cracking. (I know it is not a
replacement for reinforcement.)
Nycon fibers are more expensive $2.90 vs. $2.30 per pound.
Fibermesh leaves a "fuzzy" look. Nycon does not. If a floor cannot have
exposed fibers, like say changing room for swimmers with a bare concrete
floor where people will be walking on the surface with bare feet, then the
exposed fuzzes have to be burned off. This added cost may justify the Nylon
fibers.
Nylon fibers assorbs a small amount of water (3/4 oz per cubic yard).
Polyproplene is inert, therefore, no assorbtion. I assume no adjustment
needs to be made in the concrete mix with fibers.

Some questions:

It does not appear that Fibermesh and Nycon are equivalent. Fibermesh will
always win because of price. How can you bid both? Do you spec one and use
an alternate for the other? Do you write one product out?
What type of projects are you using Fibermesh vs. Nycon vs. WWF?
What do you prefer and why?

Jim K.



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