Concrete slab reinforcement: M100 vs. F100 fibers: finish and strength
My concrete contractor has 2 fiber choices for the slab pours : M100 and F100 from BASF. Both are polypropylene fibers, the difference is the size.
Officially M100 is only to be used to prevent shrinkage cracking. Unofficially it has been used (with apparent success) to replace light wire mesh in slabs poured in Southern Ontario. Concrete contractors prefer it when a smooth finish is requested as the extra fine fibers make the slab easier to finish.
F100 is a larger fiber, that is approved by BASF to replace light gauge wire mesh. There is no question this is the robust choice.
I have already decided to go with F100 fibers in the garage slab, but I am on the fence with regards to the house slab.
Has anyone had experiences finishing a slab with a smooth finsih with F100 fibers? I was told it finishes OK, but there may be some “fuzziness” compared to the M100, which finishes butter smooth. Is this correct? Is it possible to get a good finish with F100 fibers? I would love to hear comments from people who have used both.
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Replies
Mai Tai,
I don't have direct experience with the use of fibers in concrete slabs, but I've written articles on the topic, and I've heard reports about "fuzziness" problems.
Is there any reason why you don't want to go with one of the tried-and-true approaches: either wire mesh or a grid of rebar?
Hi Martin,
Rebar checkered pattern on chairs is tried and true (if expensive, both in setup and materials).
Wire mesh is pretty flimsy, barely useful when installed properly, and useless at the bottom of the slab (where it usually ends up).
Basically F100 fibers provides the benefits of wire mesh (most argue it is much better at preventing crack spread), with added benefit of almost foolproof installation and through slab distribution. Cost is also quite low compared to wire mesh and rebar. (an incremental cost per yard of concrete, when it is not "included" to avoid call backs).
I am almost certain I will be going with F100, but I would feel better if anyone had positive experiences with a smooth finish with limited fuzziness.
I'm skeptical about polypropylene fibers working as well as polypropylene fibers+rebar to control non-curing related crack width/height. But with a good subgrade (consider pea gravel), fibers alone could well be good enough for your use.
Thanks Jon.
I don't think the quoted fibers can replace rebar, they claim light gauge wire mesh at best. Rebar is hard to beat for flexural strength and crack resistance, but I'm trying to keep costs low. Fibers are really there to increase toughness and spall resistance.
I attached both data sheets for reference.
Mai Tai,
This article (http://www.concreteconstruction.net/how-to/fibers-in-polished-concrete_o) does not answer your specific question, but I think it suggests some options for creating a polished surface without fiber fuzz or "wormholes."