fiber mesh vs. rebar in driveway

[Johnson]

I need to get a sub to do the apron for the garage I'm building. Perhaps I'm behind the times, but one bid I received mixes in fiber mesh with the readymix and does not use rebar. I am not confident with leaving out the rebar. Is the fiber mesh sufficient by itself in giving the driveway the strength it needs? This contractor packs the gravel well and places the 4000lb concrete 4" thick. Does anyone know of any good literature or have good advice in this? Also, when going with rebar, some go with 3/8" and some with 1/2. Some place it 2' o.c. and some 3' o.c. in a grid. Is there any standard? I live in the upper midwest

Thanks, Steve

[Thor Matteson, SE]

Re: fiber mesh vs. rebar in driveway

Fibermesh is going to do a lot more good than rebar on two or three foot centers. Best thing to do is cure the slab REALLY well--at least a week. Use curing compounds, cover it with plastic sheeting (this may create odd patterns on the slab) or keep it covered with moist burlap. Also do not allow the concrete to freeze during this time. You can also use an admixture like Polyheed 997 (by Master Builders) that will reduce the amount of water needed to get the same workability, for an extra six to eight bucks per yard. This makes for stronger, more durable concrete if you don't think that the 4,000 psi mix your sub uses is good enough (or he can use less cement, pay for the admixture).

Thor

www.shearwalls.com

[Andrew R.]

Re: fiber mesh vs. rebar in driveway

Ive used fibermesh on house slabs and garage floors but not on driveways.Its not easy to work with, troweling machine churns up the cream and seems like it takes forever for the cream to tighten up to finish. I have never used rebar in driveways, good expansion joints and subgrade is all you need with a 3000 psi. 10 x 10 pours and you wont crack.

[dakota]

Re: fiber mesh vs. rebar in driveway

A lot depends on your soil conditions. Fiber wil do a great job in controing surface cracks and in most cases would replace 8x8 mesh. I do not believe it will replace rebar when needed for tensal strength. I think andrew is right Good sub base, expansion and control joints are key to long term durability. Here we use fiber in sidewalks, residential drives are 4" to 5" 3500 PSI with #3 bar 16" oc/ew and crushed lime stone not softer rock. This is because of our extreme weather changes. Somthing intersting I learned of reciently is on a new Interstate paving project the soil condition are so bad that any rebar in the concrete pavment is corrdiing in 5 years and the pavement is failing. They are now trying a new concrete mix with a fiber mesh reinforcing. The fiber is about 3 times the size that we would use. It should be intersting to see how it works.

[James Eggert]

Re: fiber mesh vs. rebar in driveway

Fibermesh is cheap insurance all-in-all.

Dakota
Usually all the rebar I have seen for highway work is epoxy coated in a green color, supposed to last assuming they paint any cuts. Also there is available "structural" steel fibers used to replace rebar for specific situations such as warehouse floors and truck docks. It is not used for an exterior application where appearance is important because the fibers can show or telegraph rust. Some of these fibers are stainless steel but there are still restrictions. SI Industries is one company that comes to mind for fibers.

[dakota]

Re: fiber mesh vs. rebar in driveway

I have been out of the industrial concreet for 10 years now. My neighbor who was on the soils team was telling me about the project. This 10 mile stretch was originaly asphalt but could not keep from buckling, then went to 10" concrete, but failed in 4 years, compleatly re engineered and re built the road bed installed epoxyed rebar double coated, up'd the quanity by 30%. Had a state engineer constant supervision of the bar instlation. the road showed signs of problems in 3 years by 6 they were re engineering and have replacement bid out to start next year. The real problem is the high acid content of the soil and ground movment. The rebar is rusting from the inside causing the concrete to fail. Now they are using some new kind of non caroding synthic fiber designed for this project, new sub base with some kind of synthetic liner. And a diferent concrete formula? I was afraid to ask how many million this was costing the tax payer. If I find out exactly what is being used I will try to mention it here.

[gdavis]

Re: fiber mesh vs. rebar in driveway

I have never had much luck with fiber mesh. It sounds better than wire, but it never seems to work out that way.

I go for solidly compacted subgrade, wire mesh (in the middle of the thickness-- go for the top and it will end up in the middle), and be sure the concrete dudes don't add water which will change the water cement ration and weaken the mix. Then if you pour in 10x10 squares (i.e. saw a control joint every 10 feet) you ain't going to have a problem. If you are going to drive heavy trucks over it, make it 6 inches thick instead of 4 inches, ands really thicken it up if it flares at the end to a point.

If you got a descent subgrade, there should be no need for rebar.

glenn

[LC Hester]

I am getting estimates for my double driveway right now. One is 4" of fiber mesh and 1 is 5" concrete with rebar. which one would be best for the cold winters of Nebraska. I am also told the fiber mesh looks hairy after installation but they are offering to seal it after 30 days . Any feed back would be appreciated.