macropolymeric fibers instead of welded wire mesh
macropolymeric fibers instead of welded wire mesh
(OP)
Has anyone had any positive or negatives about replacing a slab on grade (4" thick) with fiber reinforcement instead of welded wire meash?





RE: macropolymeric fibers instead of welded wire mesh
RE: macropolymeric fibers instead of welded wire mesh
http://www.eng-tips.com/viewthread.cfm?qid=236915
http://www.eng-tips.com/viewthread.cfm?qid=172018
RE: macropolymeric fibers instead of welded wire mesh
RE: macropolymeric fibers instead of welded wire mesh
www.PeirceEngineering.com
RE: macropolymeric fibers instead of welded wire mesh
RE: macropolymeric fibers instead of welded wire mesh
In contrast, slabs on grade may be subjected to high bending and shear stress which may require reinforcement and certainly requires attention to the subgrade to provide adequate resistance to the stress. Placement and curing are not done in the controlled conditions like precast elements, so measures to control cracking should be used.
RE: macropolymeric fibers instead of welded wire mesh
See attached fiber story I mentioned in my previous post.
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RE: macropolymeric fibers instead of welded wire mesh
RE: macropolymeric fibers instead of welded wire mesh
RE: macropolymeric fibers instead of welded wire mesh
My comment about the fraudulent marketing of plastic fibres does not apply in the case of steel fibres. Steel fibres, as referenced in PEinc's article, have many benefits, some only now being utilised fully, as in the Spanish tunnel liners.
RE: macropolymeric fibers instead of welded wire mesh
www.PeirceEngineering.com
RE: macropolymeric fibers instead of welded wire mesh
The arguments back then in the formative years of the ACI recommended practice were three-fold. There were the ductile steel fiber producers (U.S. Steel/Mitchell Fibercon), the stiff steel fiber producers (Dramix, etc.), and the glass/poly fiber producers. Glass dropped out rather quickly for general commercial use. More specialized.
Each touted its own benefits. For the poly fibers, it was the number of fibers (many, many thousands). For the ductile steel, it was strain compatibility and finishing. For the stiff steel it was strength and bond.
As hokie66 noted, fibers enhance some of the properties of concrete, but do not provide mass tensile reinforcement as would rebar or wire mesh. For instance, most of my experience (though I've used each type)has been with ductile steel fibers in concrete and asphalt, and I have seen the compressive strength and modulus of rupture of the steel fiber modified concrete increase by as much as 50 percent. About a 10 to 20 percent increase was common for both properties at the recommended "dosage" rates. Increases in strength for poly fiber concrete are gained, but not as much. These strength increases may reduce the required steel in the same manner that increasing the concrete strength by any means would do, but they don't replace the tension steel.
Crack propagation properties are changed quite a bit by fiber enhancement. Steel fibers tend to reduce cracking. Poly fibers tend to increase the space between cracks but make the cracks wider.
You can replace wire mesh in a slab on grade with fiber if you choose...since as a practical matter, you don't really need either. (OK>>>here come the arguments!). DO NOT EVER replace tension steel in a flexural member with fiber. That's patently dangerous.
RE: macropolymeric fibers instead of welded wire mesh
To follow up on your last paragraph, I don't specify wire mesh for slabs on grade or pavements. I do specify plastic fiber. I have demoed a few slabs and observed the construction of a few other. The wire mesh is always at the bottom of the slab, where it does little good.
The most important factor in preventing drying shrinkage cracking is timely sawing of properly spaced contraction joints. I believe the plastic fiber is enough help in preventing cracking to justify its cost and will give you a little more leeway in timing of sawcutting.
I don't understand why wire mesh is used in structural applications. I would never trust the workers to get the mesh right, whereas rebar is easier to place, inspect, and will remain in place during a pour. Plus, workers seem to take rebar installation more seriously than wire mesh in general.
RE: macropolymeric fibers instead of welded wire mesh
Even if you use fiber, specify the timing and location of sawcutting and make the contractor adhere to it. Late sawcutting won't be mitigated by fiber.
Heard about your new business venture...good luck.