Fiber reinforced concrete?

[mudcat]

Thanks for all the input. I talked with the local building department and ,for a monolithic slab, they require a 3ft. perimeter of wire mesh if you opt for fiber.

 

[Doc_Bob]

Thanks for all the input. I talked with the local building department and ,for a monolithic slab, they require a 3ft. perimeter of wire mesh if you opt for fiber.

What do they require if you don't use fiber mesh?
Bob

 

[Doc_Bob]

The only thing I didn't care for about fibermesh is it finishes fuzzy. The little fibers are like little hairs and if your flatwork crew isn't careful....Fuzzy wuzzy is your floor.

Humbly submitted

I had fiber mesh in my garage floor and wire mesh. But I had 1/2 inch PEX attached to the wire for future radiant heating. I had no idea what I was doing, and I still don't. The concrete guy thought I was crazy for asking for fiber mesh in a garage floor. He said he only uses fiber mesh outdoors, never in a garage. Did not cost me anymore so I said, why not. Now I have a fuzzy garage floor. And hopefully it will never crack (good base). The fuzzy fiber look like they will give great traction in the winter!
Bob

 

[mudcat]

What do they require if you don't use fiber mesh?
Bob

The 6"x6" wire mesh.

 

[Cowboyjg]

Thanks for all the input. I talked with the local building department and ,for a monolithic slab, they require a 3ft. perimeter of wire mesh if you opt for fiber.

You left out the part that you were pouring a monolithic slab. The point of the wire mesh is to create a bond between the footing and the slab. It's an uplift/shear related issue. Fiber by it'self dosen't provide the kind of strength necessary for that sort of thing. And not that I'm trying to tell your concrete guy how to do his job but sometimes the indians forget to hook the j-bolts on the mesh. I helps create that continuous connection.

Have fun with your project.

 

[sandman2234]

I am from the old school, and prefer to add not only wire to a slab, but also rebar. The last footer I poured, the city inspector took one look at the prints, another at the footer(not yet poured) and asked me what I was building, "a bomb shelter?
I go on the premise, that after it is hard, concrete is awful hard to go back and add some reinforcement. It is always better to do it while it is still in the semi solid state.
Another thing I keep a close eye on, is the water hose. Adding water makes it easier on the guys doing the work, but wrecks pure havoc on the strength of the concrete. (don't believe me? try my job as a Q.C. inspector and send a few thousand concrete samples through a press, to failure and watch the results)
David from jax

 

[CurlyDave]

Listen to sandman.

The first slab I poured, I used the wire & it cracked. Ever since then I have used rebar and they don't crack.

#4 (1/2") bar on 18" centers costs about 35-40 cents per square foot, and will prevent cracking almost no matter how bad the preparation under the slab is.

This is cheap & easy up front. Difficult & expensive after it has cracked.

 

[Dargo]

Let me first say that I am NOT an expert on concrete; but I am now getting close to the 1000 yard mark on concrete used at my place and I"ve been involved in every pour. I am a firm believer in using plenty of steel in your concrete. In my last pour I used not only #5 rebar (.625 of an inch in diameter), 6 gauge wire matting, the intermixed fiber in the concrete, but also 5000 psi concrete. This is in 6" thick 12' X 20' pads in my driveway. The floor in my barn ranges from 10" to 12" thick and has #4 rebar on 18" centers along with the 6 gauge wire matting but no fiber. I also have a couple hundred yards of exposed aggregate concrete in my porch. Unfortunately, I still have about 700 feet left to do in my driveway as well as a 20' X 80' pad behind my barn.

Anyway, the only point I wanted to make is that no matter what you do, it will be the exception rather than the rule to not have any cracks in your concrete. It's taken almost 10 years for some cracks to appear, but I do have hair line cracks in most all of my concrete. To me though, the most important part is to try to make sure that the concrete does not move when it cracks. All of the steel in my concrete has kept any crack from getting any larger or having one slab drop lower than another etc. Most every old concrete guys I've used have told me that all concrete gets hard and it cracks. It's just controlling the cracks that is the art. You want it to crack in the stress joints incorporated with your pour. If it cracks there you shouldn't be able to see it if you have all of your joints filled with concrete caulk.

P.S. Since I've had to tear out an area or two that didn't come out to my satisfaction, I can tell you that the exposed aggregate concrete seems the hardest to cut and to tear out. Why? I don't know, but it sure is a bugger to rip out.

 

[GeneD14]

"If it cracks there you shouldn't be able to see it if you have all of your joints filled with concrete caulk."

That is some good advice. Up here were we get alot of freezing and thawing if you don't seal a crack over time it will expand wider.

For my driveway I used 5" thick 6,000 psi concrete with heavy "road mesh" wire and after 3 years just one hair line crack over the culvert at the end of the drive.

I also saw cut it into 8' squares to control the cracks. Then I used concrete caulk to fill them and prevent spaulding. The caulk that I used was very thick and difficult to spead, almost like bubble gum. I got it at Menards.

We have a delivery truck that stops by monthly that is 26,000 GVW and he usually is loaded heavy, so I still get concerned. So far - so good.

 

[sandman2234]

I am not familiar with what the cold does with concrete, having lived in the south most of my adult life, but do realize that the salts used on the highways are a concrete killer.
However, a concrete slab, properly prepared, and properly poured is quite possible to do and not have c r a c k s here in the south.
My driveway is a perfect example. It was poured sometime around the time this house was built, in 1965, and has no cracks. The garage was poured around the mid 70's and it has no cracks. Why? Because the guy that poured them was a stickler for details and left nothing to chance.
I accidently broke one corner of the last slab with a backhoe while doing some clearing at the end of the driveway. It broke, revealing wire and rebar.
Anybody ever pour any prestress???
David from jax