Fiber mesh and floor coatings

[brownsmustang]

Ok, I just ripped out the old asphalt that was in my recently purchased shop. I'm going to pour a 5-6" slab, #3 rebar, 10 mil vb, and was considering adding the fiber mesh as well to the mix. But I know some of the mesh will be at the surface and even loose ends sticking out. How would that affect my paint on floor epoxy? Could I burn them off before coating? U coat it says I don't need to grind the floor but I need to use an acid. Would the acid remove the fibers?

 

[benwah]

You should always grind when possible. What type of floor are you doing?

 

[brownsmustang]

U coat it.

 

[brownsmustang]

I asked them, and they said as long as the concrete is uncoated, sanding or grinding is not necessary.

 

[Renegade1LI]

I hate fiber mesh, if you’re using a legitimate rebar matt and expansion joints there’s no need for mesh. The subgrade is very important, should be 95% compacted stable material or stone, my masons hate finishing mesh, what you can do is add a hardener if you are machine finishing, we add that alot for industrial floors.

 

[benwah]

I asked them, and they said as long as the concrete is uncoated, sanding or grinding is not necessary.

I mean are you doing a solid color, full flake, partial flake, metallic, something else? How thick of a system are you applying?

Is your slab going to be power troweled? If so I'd highly recommend grinding to open up the concrete.

I personally never burn the fibers, I prefer to solvent wipe the floor after grinding. It seems to make the fibers lie down. I also always run a quick sanding screen on a swing buffer after my prime coat as well. This takes care of any fibers or roller lint that may be protruding. It also helps with the mechanical adhesion between coats.

 

[LegacyIndustrial]

Rose-bud torch, the fibers are polypropylene, it doesn't take much.
Wipe the floor clean afterwards.

 

[ConCretin]

You don't say how big your shop is but unless it is very large, I wouldn't bother with the fiber mesh. Fiber simply limits early age shrinkage cracks. This allows you to space out your control joints a bit and might buy you a little more time to get them cut.

Fiber doesn't eliminate the use of control joints unless the need is marginal to begin with based on the size of the slab and performs performs no long term function. Seems like an unnecessary cost and hassle.

If you are going to invest in an expensive floor coating, I'd consider upgrading the vapor barrier to a 15 mil product like Stego unless the soils in your area are very dry.

 

[1MtnGoat]

Don't spend the $$ on the fiber. Put 6 x 6 #10 WWM (highway mesh) in your floor. Make sure that when the floor is poured the mesh gets pulled up to the middle of the concrete. Cut and fill the expansion joints ASAP (cut same day if possible). Control joints are a must. The question is not if your floor will crack but where. Even if power troweled (unless done to a glaze) as long as the floor is clean no grinding is necessary. Allow 30 days to cure and coat with your coating of choice. BTW Hellfire coating from Legacy mentioned above is great! I have over 3k sq. ft. of their product in my shop and am well pleased with it.

 

[Dh3256]

Control joints are a must.

Agree on control joints if you cannot keep the slab soaking wet for a month.

However, if you are able and willing to keep the slab wet for a month, control joints are not necessary and the slab won't crack. It's a good solution for a home project but impractical for a contractor to do.

Concrete cures through a chemical reaction that requires water. If there is not enough water, the reaction stops and cannot be restarted. If you can keep the slab soaking wet, that ensures there is sufficient water and the reaction continues. After a month the concrete is in the 90% range of strength and will be stable without control joints.

I have done several large slabs this way with no control joints or cracks.

 

[Renegade1LI]

We recently built a bus garage in nyc 390,000 sq ft of concrete, no fiber, all reinforced. The design called for a steel floor hardener that gets power troweled into the finish & then a clear sealer. They build these for easy maintenance & longevity, that's how I would do a new shop floor. If you are epoxy coating, usually calls for shot blasting prior to coating, the manufacturer will spec out a roughened surface similar to sand paper grade & you can rent a blaster & do it yourself if you want. Or ask the vendor if a broom type finish is acceptable & what type of curing compound is compatible. We do a lot of epoxy coatings for NYC DEP & there spec always refers to the manufactures install procedure, I'm not familiar with U Coat but I believe it is water based, I would stay away from water based for an industrial floor, personally I like a machine troweled finish with a hardener & than sealed. You should look at some pics of surface hardened concrete that is polished, very impressive when done correctly.

 

[Armorpoxy]

Hi, you will need to burn off the fibers, otherwise they have a 'hair gel' effect.

Acid is worthless on fibers and even grinding usually leaves quite a bit of fiber residue.

Stick with a 100% solids system like www.armorcladepoxy.com or similar.

 

[brownsmustang]

You don't say how big your shop is but unless it is very large, I wouldn't bother with the fiber mesh. Fiber simply limits early age shrinkage cracks. This allows you to space out your control joints a bit and might buy you a little more time to get them cut.

Fiber doesn't eliminate the use of control joints unless the need is marginal to begin with based on the size of the slab and performs performs no long term function. Seems like an unnecessary cost and hassle.

If you are going to invest in an expensive floor coating, I'd consider upgrading the vapor barrier to a 15 mil product like Stego unless the soils in your area are very dry.

32x48

 

[ConCretin]

32x48

The typical plan for a slab that size would be two cuts the long way and three the short way creating 10-8 x 12-0 panels. Since fiber probably wouldn't prevent random cracks if you eliminated a cut or two, I don't see the benefit.

With that said, timing is very important. Ideally you'll cut your joints with an early entry saw right after finishing or worst case, the following morning. This will create cracks where you can't see them and relieve the tension from drying shrinkage so you don't get them where you can.

That is a nice size shop. Congrats and good luck with the build.

 

[65ranchero]

I was also in the fiber/ no fiber dilemma when I started my planning of the garage/shop
After all my research I came to the conclusion that no fiber was the way to go.
The one thing I did do was to opt for dyed concrete when it was mixed at the plant. (Many different colors) after it was poured it was power troweled and I couldn't be happier.
then sealed, with rolled on concrete sealer, (gas takes it right up, ask me how I know)
got to reseal it soon after a good power wash

 

[brownsmustang]

The typical plan for a slab that size would be two cuts the long way and three the short way creating 10-8 x 12-0 panels. Since fiber probably wouldn't prevent random cracks if you eliminated a cut or two, I don't see the benefit.

With that said, timing is very important. Ideally you'll cut your joints with an early entry saw right after finishing or worst case, the following morning. This will create cracks where you can't see them and relieve the tension from drying shrinkage so you don't get them where you can.

That is a nice size shop. Congrats and good luck with the build.

I think I'm going to forgo the fiber and not have to deal with it. The early entry saw is new to me,I had no idea they made such a thing. I'm planning on renting one when the time comes. Thanks for you input.

 

[ConCretin]

I think I'm going to forgo the fiber and not have to deal with it. The early entry saw is new to me,I had no idea they made such a thing. I'm planning on renting one when the time comes. Thanks for you input.

An early entry or soffcut saw has a very thin blade that turns into the slab through a plate that presses down on the concrete to keep aggregate from getting dislodged. They can be used immediately after finishing, which relieves the tension before random cracks occur. Cracks often occur before you cut if you wait much longer.

No reason you can't do it but most finishers up this way own the saws and do the cutting. It may be possible where you are but we can't rent early entry saws.

 

[brownsmustang]

An early entry or soffcut saw has a very thin blade that turns into the slab through a plate that presses down on the concrete to keep aggregate from getting dislodged. They can be used immediately after finishing, which relieves the tension before random cracks occur. Cracks often occur before you cut if you wait much longer.

No reason you can't do it but most finishers up this way own the saws and do the cutting. It may be possible where you are but we can't rent early entry saws.

This is gonna be a diy job start to finish. My cousin is kind of the gen con as he's done this type of work before and several shop slabs in the past, I checked and can rent the early entry saw from my local rental place