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Old 04-19-2019, 09:57 AM   #1
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concrete with fiber


framing to pour a slab (15' x 30') for a storage shed - being told that the fiber mix does not require rebar, but am curious if its easy to work with? anyone have any tips, or suggestions?
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Old 04-19-2019, 10:51 AM   #2
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Re: concrete with fiber


That's a loaded subject and is not as simple as that, don't let a contractor tell you otherwise. It's mostly a labor saver for them. Fiber mesh has a different purpose than WWF or rebar. Every situation is different and multiple solutions may exist. In a storage shed you're probably not concerned with exposed fibers in sawcuts and such, or worried too much about tensile strength or structural cracking.

But with workability, you do have to be careful and not over-work it being float happy. Sometimes you may be focused on some errant fibers and make too much cream.
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Old 04-21-2019, 02:30 PM   #3
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Re: concrete with fiber


how thick is the proposed floor ? aci doesn't like anything in floors 4" or less,,, wire only helps when its placed correctly at the vert mid-point +/- 1/8",,, they also like 2" of 'cover' top & btm when in slabs,,, we usually only see fiber in warehouse floors - not sheds or exterior conc,,, when it 1st arrived on the scene, specifiers were gung-ho about it,,, now we don't see that much of it
suggestion - no wire mesh - it usually comes in rolls & very few have necessary equip to make it lie straight/flat,,, rebar doesn't add compressive strength but it does add flexural strength
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Old 04-21-2019, 03:01 PM   #4
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Re: concrete with fiber


I like fiber. I've used it on (5) buildings I've built and had good results on each one.

It's best feature is if you do end up with cracks it holds the concrete together at the surface so the hairline cracks don't start breaking apart.

But fiber is no substitute for reinforcing steel.

Most reputable lumber yards will have, or can get, reinforcing mesh in sheets (not the rolled type that stadry talks about). I'd suggest 6 gauge, 6 x 6-W2.9 x W2.9 wire mesh in 8' x 20' sheets.

Use those mesh sheets, overlap them 6", wire them together with re-bar wire, and set the sheets on concrete dobies. Don't allow the contractor to lay the mesh on the sub-grade and then pull it up as they place the concrete. That never works, it's half assed.... tell them that.

That's what I did on my barn slab. The 6 gauge mesh is a heavy enough gauge that when the folks pouring the slab step on it the mesh pops right back up into place.

One other thing, none of this matters much if the sub-grade isn't prepared properly (compaction) and the correct materials weren't used (crushed aggregate).

Here are a few photo's. Good luck with your project.

Concrete Dobies Link
: https://www.whitecap.com/shop/wc/p/d...th-wire-123704
Attached Thumbnails
concrete with fiber-dobie-003.jpg   concrete with fiber-dobie-002.jpg   concrete with fiber-dobie-000.jpg   concrete with fiber-ready-pour-004.jpg  
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Last edited by HenryMac; 04-21-2019 at 03:14 PM.
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Old 04-28-2019, 09:27 PM   #5
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Re: concrete with fiber


The standard fibermesh don't effectively replace steel in concrete, even the manufacturers backed off on these claims years ago.

THere are mono-filament and macro fibers out now that have the ability to replace steel, but they are far less common, much more expensive, and offer additional placement and finishing challenges that the smaller fibers don't.


At typical dosages, the benefits of synthetic fibers occur only during the first few hours after the concrete is placed; after that time, they provide no real benefits. Many studies have verified that synthetic fibers, unlike wire mesh, reduce plastic shrinkage cracking. Plastic shrinkage cracking occurs as the concrete makes the transition from liquid to a hardened slab. "Synthetic fibers help with avoiding plastic shrinkage cracks, but they don't do much after the concrete hardens, in terms of providing a lot of strength for the slab later on," admits Hal Payne, marketing services manager at Synthetic Industries, the manufacturer of Fibermesh.

https://m.homeadvisor.com/article.sh...esh.13698.html
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Old 04-28-2019, 09:34 PM   #6
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Re: concrete with fiber


Quote:
Originally Posted by stadry View Post
how thick is the proposed floor ? aci doesn't like anything in floors 4" or less,,, wire only helps when its placed correctly at the vert mid-point +/- 1/8",,, they also like 2" of 'cover' top & btm when in slabs,,, we usually only see fiber in warehouse floors - not sheds or exterior conc,,, when it 1st arrived on the scene, specifiers were gung-ho about it,,, now we don't see that much of it
suggestion - no wire mesh - it usually comes in rolls & very few have necessary equip to make it lie straight/flat,,, rebar doesn't add compressive strength but it does add flexural strength
It feels like we've been through this a million times, but ACI doesn't say anything about 2" of coverage in this application. 1.5" is there recommendation on exterior slabs exposed to weather. Interior floors over vapor barrier can go down to 3/4"coverage.

Nice to see you're still kicking around, young buck!
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