confused on fibermesh

[prostreet]

I am having 4" of concrete poured on 2" foam boards that have bosses that hold pex tubing. My contractor is using fiber mesh with 4000 psi concrete. I heard that the fibers make people itch. How do you remove fibers before i epoxy floor? One other question does the manifold need to be in center of garage for pex tubes?

 

[Duane]

I poured a concrete walkway last fall and purchased my concrete from U cart concrete. They told me about fibre mesh as well and showed me a bag of it.
It is a powdered like additive that is mixed in with the concrete to make it even stronger. It was recommended to me as a substitute for wire mesh or rebar. There should be no fibres to mess up your epoxy. You won,t even know the fibre mesh is in there.

Duane

 

[rburke65]

I have heard that you might have to take a propane torch and burn the "hairs" off before you start your floor prep.

 

[boiler7904]

Like mentioned before, you use a torch to burn the fiber fuzz off the surface. May have to do some light sanding / grinding as prep after the torching. Wear a particulate mask while doing this.

Manifold doesn't have to be in the center of the garage but the overall lengths of the loops should be as even as possible.

It's a good idea to keep the lines pressurized (with water or air and a gauge) during the pour and cutting of joints. A drop in pressure shows that a line's been cut and the approximate area to start investigating if you're paying attention. During the pour, water or air bubbling will mark the spot for you. I'd also have couplings and extra pipe on hand along with the required tools . If a line gets nicked during the pour, it's easy to make a repair without holding things up. After the fact means chipping out and patching a new floor. Make sure you know where and how deep in the slab the pipe is when your control joints are cut and set the saw depth accordingly.

 

[darkk]

Fibermesh does NOT replace wire mesh or rebar. Fibermesh is to help prevent surface cracking during the cure process. After the cure, fibermesh ceases to have any other function. I would use either wiremesh or rebar along with fiber mesh and cover the bottom before the pour with at least 6 mil plastic with taped seams. Keep your surface very very wet (soaking wet) for a minimum of 7 days to help set the concrete. research this very well before the pour because most of the people doing the concrete work are only interested in pour and smooth...then gone. At least one person there should have an idea what's going on. That person should be you. Save yourself from problems after the pour...educate yourself.

 

[Wastedwagesracing]

Fibermesh does NOT replace wire mesh or rebar. Fibermesh is to help prevent surface cracking during the cure process. After the cure, fibermesh ceases to have any other function. I would use either wiremesh or rebar along with fiber mesh and cover the bottom before the pour with at least 6 mil plastic with taped seams. Keep your surface very very wet (soaking wet) for a minimum of 7 days to help set the concrete. research this very well before the pour because most of the people doing the concrete work are only interested in pour and smooth...then gone. At least one person there should have an idea what's going on. That person should be you. Save yourself from problems after the pour...educate yourself.

I have seen you post this several times. Do you have a link to a good site on this subject? I have read up on it but like lots of stuff on the web you don't know what to trust. Thanks

 

[chickenhauler]

I have seen you post this several times. Do you have a link to a good site on this subject? I have read up on it but like lots of stuff on the web you don't know what to trust. Thanks

I don't know about any links on the subject, in fact I'd say the majority believe that fibers can replace reinforcement. From my experience pouring, I would have to say that fibers do NOT replace reinforcement, but they do still have some degree of holding strength after the cure. I HATE them for any type of troweled/smooth concrete, because for some reason, I end up with a ball of them screwing up my finish. I didn't use them for my garage floor for that reason.

 

[Charles (in GA)]

After seeing fiber used in concrete, I cannot see how it does any real good at all. It certainly won't replace rebar or wire mesh, it might help a little, but I have seen slabs done with it that were slick finished and it was much more difficult for the finishers and just really wasn't right (finish wise) when done.

Honestly seems to me to be more of a gimmick than anything else.

Charles

 

[Falcon67]

I went 3/8 bar on 18" centers and passed on the fiber option. I have several surface cure cracks, but that's expected. I'd worry about steel, footings and beams first.

 

[69dz302z28]

I fully agree with darkk on this subject. In my last building I was sold on the fibermesh, what a disappointment! It is cheaper and easier than rebar, but you definitely get what you pay for. No small surface cracking, just rather large ones!! After working on your back under a vehicle, you feel as though you were rolling around in a pile of glass insulation, on an untreated floor. It is a pain in the rear to seal. The building was built in 98 and still had fibers coming loose through cheap sealant until I moved in 09. Just had slab poured yesterday in my new 40x30, rebar every 2 foot in grid pattern pulled up into the concrete over vapor barrier. Did it right this time, except for the 110 degree temps we had yesterday! Soaking with lots of water.

 

[ConCretin]

Fibermesh does NOT replace wire mesh or rebar. Fibermesh is to help prevent surface cracking during the cure process. After the cure, fibermesh ceases to have any other function. I would use either wiremesh or rebar along with fiber mesh

X2!

Fibermesh resists early cracking while the concrete is still essentially plastic. It will control shrinkage cracks long enough to relieve the tension with saw cut control joints. It's fine as long as you understand what you are buying and what you aren't.

 

[pauls340]

M2C's...There is no know disadvantage to using fibre in your concrete. The American Concrete Inst. says, and we know this from many hours and $$$$ of research, fibre makes your concrete stronger. Those fibre's don't stop working. Think about it. You have a polyurethane, or poly something, strand that is holding adjacent concrete together. Even when it snaps apart, you then have two shorter strands. THAT was a small and good investment AND no it doesn't replace steel. Also, I believe, it has no affect on dry shrinkage of the surface. Put a post applied penetrating concrete sealer in that slab and you're good to go.

 

[pauls340]

Also, your foam boards will not stop moisture drive up to and thru the concrete. If you, they don't put a good moisture barrier, plastic, under that foam, then you need to spray your concrete with a good penetrating sealer/ vapor proofer....this is where i'm supposed to say Vapor Lock, but i'm not going to.

 

[Edger]

Here is a datasheet link to steel fibres which are much stronger than poly fibres http://www.bosfa.com/docs/EE FIBRESTEEL.pdf
(sorry about the spelling downunder)

 

[discbrks]

What is the consensus of fibers with wire mesh, troweled smooth and a sealer applied? Does the "fuzz" have any effect on the sealer?

 

[brownbagg]

yes you can see the fiber after you expoy the slab, because I am looking at it right now on my slab but after ten minute you forget all about it. Fiber does not replace rebar. wire mesh does not replace rebar. fiber and wire mesh are closer in product design than rebar. After curing both does minimal. Rebar is for load factors, and thats all, if there is no load factor, rebar does nothing. Rebar controls the bending of concrete due to load which creating cracking and system failure. Fiber and wire mesh can never do these jobs. Never confuse rebar with wire mesh. Never compared them, they do two different jobs. Now a typical slab on grade like house slab or garage slab, according to the calculator, rebar is not needed. that doesnt mean you should not do without it if you want rebar. Not talking about slab in shop where you have point loading. Rebar doesnt control cracking except in a load factor. majority of cracking is cause by uncompacted sub soil, curing, or process of placement (no vapor barrier, too much water, concrete getting hot, over working)

 

[Frank The Plumber]

I have a fibre mesh floor in my shop, you can't see any fibres sticking out of it.I still skreeded in rebar and mesh with a poly liner on the bottom over a foot of 95% compacted stone in 3" lifts. It adds strength to the floor, I used it because I saw it used on a trucking terminal and the engineer claimed it was 1/3 stronger than straight mix. It's held up OK.

 

[Neuswede]

For a pour over PEX, a pump truck is typically used to minimize damage to the pipe. The boom can get the concrete to every corner of the building quickly, and without wheelbarrowing loads of the stuff over your pipe. Leave your pipes long (about 5' extra) and set them on a piece of plywood or board that the manifold with mount to temporarily. Remember to insulate the perimeter of the slab as well. Just 1" of polyfoam (Blue board) is enough to insulate the slab against the foundation. 6 Mil vapor barrier, with at lest 6 inch overlap and taped joints is recommended. Some radiant designers are also recommending as much as 35 Mil vapor barrier now.

I am about 1 month away from my pour, which has steel, radiant and 4000PSI with fiber mesh. I had a local designer do my tube layout, and I specified the exact location for the manifold; the computer then calculates the heating requirements and loop layout based upon openings and space to be heated.

 

[darkk]

I have seen you post this several times. Do you have a link to a good site on this subject? I have read up on it but like lots of stuff on the web you don't know what to trust. Thanks

I did a considerable amount of searching and reading about concrete and proper curing before and after my pour. To answer a few questions: Fibermesh does leave little hairs sticking out of the concrete. It can be removed by burning them off with one of those propane weed killer torches. Fibermesh helps ONLY during the cure process to help keep the surface from getting spider cracks. After cure, fibermesh does nothing., It serves no other purpose. A plastic of 6 mil minimum taped at the seams and should be placed under any concrete slab especially if it is an inside floor. The concrete must be cured properly by one of several ways to avoid structural cracks. Myself I used the keep it wet process. I kept it soaked 24/7 for a solid 7 days.

 

[hockey88fan]

I understand the reasoning behind putting xps insulation where the pad meets the wall. But my question would be where then do you put the expansion joint material? I'm having trouble picturing this. My case is the slab will be poured against a concrete wall.

 

[ConCretin]

Rebar is for load factors, and thats all, if there is no load factor, rebar does nothing. Rebar controls the bending of concrete due to load which creating cracking and system failure. Fiber and wire mesh can never do these jobs. Never confuse rebar with wire mesh. Never compared them, they do two different jobs. Now a typical slab on grade like house slab or garage slab, according to the calculator, rebar is not needed. that doesnt mean you should not do without it if you want rebar. Not talking about slab in shop where you have point loading. Rebar doesnt control cracking except in a load factor. majority of cracking is cause by uncompacted sub soil, curing, or process of placement (no vapor barrier, too much water, concrete getting hot, over working)

I don't think its fair to say that mesh and rebar don't help control cracking at all. By adding tensile strength to the concrete section, they all resist shrinkage cracks. Granted, fiber, wire or bar aren't capable of completely eliminating cracks - for that you need to post-tension - they all help in varying degrees. Above a certain size slab, the only option is to manage and 'hide' the cracks with control joints

The depth of a typical garage slab isn't adequate for rebar to do much to resist applied loads. Loads applied to a slab go right to the sub grade, which is why it is so important. The slab must be able to resist a flexural load but the sub grade takes the brunt of it.

The major advantage to using wire or bar is that they hold the crack together keeping it from widening and/or lifting.

Cracks in slabs generally fall into four categories; Surface cracks caused by finishing problems, shrinkage cracks that occur early in the curing process, thermal cracks (uncommon) that result later with seasonal change and structural cracks that result from over loading the slab/sub grade.

No reinforcement will help with surface cracking. All 'help' with shrinkage cracks and to some degree thermal cracks. Rebar helps a little with structural issues.

Not trying to be disagreeable brownbagg. Just thought I'd elaborate on your comments.

 

[Neuswede]

I understand the reasoning behind putting xps insulation where the pad meets the wall. But my question would be where then do you put the expansion joint material? I'm having trouble picturing this. My case is the slab will be poured against a concrete wall.

From what I've seen done, no expansion material is placed between the inside of the foundation wall and the slab (around the perimeter of the slab); you have 1" of insulation in that area which aids in with any expansion issues.