Laying a concrete slab question

[Scoot]

I'm going to put a concrete slab in my back yard this summer. Because my driveway is SO sloped, I've decided to put a slab in back to put up a basketball hoop. I'm being told that I could skip putting rebar in the concrete if I put some additive in the cement. I think the additive was some fiberglass product.

Does anyone have any experiece with this? Is it an acceptable alternative to traditional concred/rebar? When I asked the "concrete expert", all he said was that the concrete with additive (and no rebar) would last considerably longer than I would.

[DOC33]

The "additive" is called Fiber mesh. It is fiberglass like you said. The fibers mix into the concrete and hold everything together. Some people don't like to use it on exterior slabs because when you broom it, it can collect and make little bumbs. Personally I would use the fiber mesh, with traffic the bumps wear off. No need for rebar in a slab like that. The other option would be wire mesh, chicken wire. With the fiber mesh, you don't have to worry about pulling it up in the concrete as you would with wire.

[burl]

Used a bag of fiber mesh on a 6x20 kennel run.Put two cuts in width ways equaly spaced on the length and it has held up better than any of my other slabs.I broomed the finish but did not have any problems with it balling up.Burl.

[JohnMickish]

Rebar isn't that expensive, and is it really worth the savings to have an cracked and uneven slab? I am not a concrete guy by trade ( have poured more than my share however) but I do work in the trades and I can say that I have NEVER seen a professional concrete crew use fiber mesh instead of rebar. That alone should tell you something. It would probably be fine for something narrow but I doubt you would get 15+ years out of it for a B ball court.

I am guessing that you would also want to pour your slab a bit thicker with mesh insted of rebar. On a 10X20 slab at 4" you would need 2.5 yards and at 6" you will need 3.7 yards of mud. Now at todays cost of concrete that would more than offset the cost of rebar. Just my .02.

[LundExplorer]

I used fibermesh concrete for a few pours I did for my driveway.

I used rebar around the perimeter and cross braces like an X across the diagonals.

[hanson]

Structural Engineers on our commercial projects specify 6x6 WWF (Welded Wire Fabric) for concrete slabs. Its essentially a grid of small diameter steel with 6" x 6" openings... "fancy" chicken wire. You really shouldn't need rebar unless your driving heavy loads on it.

The problem with fiber mesh reinforcement has been mentioned already, the top of the slab is "hairy".

[kb1965]

I have a fiber mesh slab in my shed. With fiber mesh, once the slab is cured take an ice melting torch, kind used on a 20 lbs cyclnder and burn the slab. The fibers will burn off, otherwise if you don't and walk on it barefooted you get slivers.

[Shack]

If I were selling you a slab, fibercrete or FRC (fiber reinforced concrete)would be considered an up sale. If you are interested in what mix to poor, call your local dispatch. They will inform you of the do and do not’s, even if you do not buy anything at that time. I recommend Aggregate Industries. FRC is a lot more per square yard than a reg. 6 bag mix. Rebar is cheap, or maybe not with the price of steel now a days. When I priced last job of the year, last year. I still found straight 6 bag mix, 4000 psi and rebar was cheaper. Also for what you are doing ,it is all you need unless you are on clay or bog. If that if the case, wire mesh and rebar are recommended . Also may think of switching to a 6000 psi injection. Remember (I hate when people say that), this is Minnesota and not matter what you do, there is always a chance for cracks and heaves. When concrete is prepped and done correct. It will last for years. Also seal concrete the same day as it is poured. Pour in morning, spray in after noon. Concrete is cleanest at this time and sealer will adhere much better and for longer period of time. For a dog kennel and basket ball court, fiber is over kill. Also an add. Cost, that is usually marked up. If a customer really has hart set on FRC, sure I’ll sell it to ya and make some money. I say above statement, because I like to help fellow F.M.er’s out. In real life, I would push any up sales I could.

Best regards,

SHACKBASH

P.S.

I know the American male’s view on things is over kill, but you could go with rebar 4’ on center and no outside rim. Again, if ground prep is done right, this is all you need for a slap that will never see traffic or structural load. This is if you want to save money. Others will go to there grave saying 2’ on center, with outside rim. The choice is yours. Steel isn’t cheap, but you only poor once and have to live with what happens in future. Good luck!

[Shack]

Also do what ever makes you sleep better at night. I threw rebar in the slabs around my house, because I have it laying all around. For your application, you rely do not need rebar if every thing is done right!

[JohnMickish]

Key words? "Everything done right."

[bigswede]

I also work in the industry and on the office and retail side of things and Fiber mnesh IS NOT a direct substitute for mesh or rebar. It does help, but is not a substitute. For what you are talking, the most I would do is some 6x6 mesh. Anything else would be overkill. Just my $.02

[Meat-Run]

Scoot,

If I may steal your thread a little bit? I'm thinking about doing a 26X30 garage with for my boat and truck this summer. What is the difference between rebar an steel mesh(?) sorry don't know what it is called. Plus can anybody give me a questemite on what to expect for cost on this size of slab?

1. if contract to have done?

2. if I do it my self and just purchase the material and cement?

thanks,

MR

[Shack]

For that size slab you around 10 ¼ to 10 ½ yards needed (includes 5%-10% surplus). I would say if you do it your self, around $1500.00 with tax and rebar cost’s. Also figure in food and beverage costs for friends you have help or side money. If you have an outfit do your slab, you are looking around $6000-$6500 (includes tax, form set up, broom finish rebar and install of rebar). Now any extra’s will drive price up, like burn finish, color, fiber, stamping, saw cutting instead of tool cut and additives in concrete. The list goes on and on. This should put you right in the ball park. I figured a little high, but all depends on what sources you use. If you do it your self, plan on having about 4-5 guys on hand. The more help the marrier. Make sure someone knows how to handle a bull float and finishing tools. Its a good size slab, but can be done by noon on a Sat. morning.

Best regards,

SHACKBASH

P.S.,

SAW CUT!!!!!! It looks much nicer and you can roll a tool box over with out getting stuck.

[luckey]

Timely post. I started staking out the slab for a garage. It's a 28X36 garage with a 12X20 attached porch. That's about 1250 sq ft of slab. I haven't decided on fiber, mesh, or rebar. One end of the garage will need about 18-20 inches of fill so maybe rebar would be best.

[Shack]

I really push the use of rebar, because of my experience with both steel mesh and rebar over the years. Another benny rebar has over mesh is it is easier when pulling the strengthening device you have chosen up while pouring concrete. I feel both steel mesh and rebar are about the same strength wise when used correctly. When it comes to pulling up on them during a pour, rebar requires less man power to bring up. One person can pull up on 2’ on center ½” tied rebar and lift the same area or more as two men lifting steel mesh. It one less hassle on the job. Now if you are doing bends or slops (slopping stairs down hill), it easier to use mesh than bending rebar. Also rebar is cleanest way to tie into concrete already there. Drill hole and bang in stub and tie off. You can tap-con and wire tie steel mesh in, but its a lot of work and I personally think there would be a chance of shifting. Again, do what ever helps you sleep better at night. Once tools are cleaned up and loader is loaded, the warranty expires. Concrete has a tail lights out warranty in residential, as soon as the tail lights are out of sight the warranty is over. Good luck.

[RipJigger]

I run a concrete plant and you wouldnt believe how many times I get asked this question and I'll give the same answer.There is no substitute for rebar,fibermesh is designed as a secondary reinforcment,It should be used in conjunction with rebar.It might be fine on very small projects,it will help to keep hairline cracks out of the slab but offers no protection from the shearing forces from the freeze thaw cycle.I personally wont pour anything or warranty any slab without rebar.If you dont want to use rebar I would at least use the woven wire mesh.I dont have anything against fibermesh it's a good product but not a primary reinforcement.

[Shack]

I got a good one! Any of you concrete guys use this during pour and finishing. I say many things when pouring, but this one usely gets a laugh or two from my guys. "Hey, hurry up over there. This isn’t like were finishing the front of a liquor store here" or just "Hey this isn’t no liquor store, get a move on it". Its all fun and games when your setting up. A few laugh's, a few jokes. All of a sudden, one of the guys hears the sound. The sound could be the truck coming down the road or the reverse beep. It all changes at this time. People seem to get in a different mood. Father will swear at son. The puddler takes the brunt of it. One of the men on the rod is yelling at the other. The only people who keep there cool is the truck driver and bull floater. They do not say a peep, unless there is a low spot and puddler throws to much or to little. Ahh, the pour life. You have to love it. When your finishing, every one calms down. Jokes start to fly. People start to laugh again. Oh the sound of finishing trowels scraping away. Finally, time for a beer.

[DOC33]

Shack-

Nothing like the sight of the truck to send the grunts flying. Running for boots, rakes, handles, etc. Throw in a fresh dip or light a new smoke, cause it's go time. You are exactly right about the tempers being a little shorter when the trucks on the job. Once the rod strikes off the last corner, the anxiety level drops immediately. I remember the days running the rake thinking, man I wish I could run the bull float. Never failed, after every pour, my old sup would say "This job is sooo easy, women and childern could do it."

"This ain't a bar" and "Tail light warranty", classic finisherisms.

[iffwalleyes]

Scoot where you live is the worst soil in the world. The dump is only good for farming. The stuff is constantly moving. I personally for what you are doing wouldn't get the fiber mesh in the concrete waste of money. Then do a price comparision I like the wire mesh that Hanson mentioned for smaller jobs. It should work really good for your situation. Otherwise a single mat of #3 or #4 rebar tied 16" on center should be good for a basketball court. I guess it is really up to you. If you don't reinforce it it will probably crack in the Red River Valley.

[Scoot]

Thanks to all for the info!

[dogs]

The biggest thing to concrete holding up is the base. Uneven soil mix and moisture are your worst enemy. Designed and built roads for years. The biggest thing with your slab is when the ground freezes or settles that the whole slab does it in unison.