Rebar in Concrete Pier

[oakey]

I was looking at some member's builds and I got to thinking about something. I had helped build a shop with my uncle one time and we used 4 foot or so concrete pier forms and I think he was using fiber mesh concrete mix from the company, not exactly sure of the name but I remember it was a little more per yard and had some type of synthetic "bonding material" in it. For something like a pier form, is rebar required or just added insurance? I know that we put three pieces in his and the driver was saying that technically we didn't need to do that with that mix being put in them.

[dug]

I would say that though with a fiber reinforced mix you may not technically need the rebar, but it is relatively cheap and will definitely make the concrete stronger. I would use it.

[MountainDon]

I've never used it myself but have read that it replaces steel bar or wire mesh. There are different grades, sizes. It is supposed to save the cost and labor of the steel. Theoretically doing away with the steel could be a good thing. Steel rusting within concrete takes up more space and can crack concrete. No idea on real world experience.

One problem the park service has with maintaining historic buildings, forts and piers is that the iron that was used in many corrodes and actually explodes sections on old works.  

[oakey]

I know alot of people that agree with you MountainDon. Some old school builders in my area don't like the idea of of metal in the concrete due to the reasons you stated. I have some pier work myself coming up and I am thinking about going with the fiber blend without metal.

[MountainDon]

I believe it takes a very long time for that to become an issue though. It helps a lot to have the rebar or wire mesh fully encased within the concrete. Driving rebar into the ground for a vertical column id bad as it provides a pathway for moisture. Eliminating the steel/iron does seem to offer a lot.

[Don_P]

The fiber isn't up to the task, it's great for preventing shrinkage cracks and for light loads but it takes continuous rebar to develop real tensile strength. They use steel not fiber in bridges even knowing salt will eventually eat it causing spalling and eventual replacement (they use epoxy coated nowadays but even there it will one day fail). I think I've read that rust is 5 times bigger than the steel. Rebar needs at least 3" of cover, more is better, keep the O2 away and it slows rust, hook the ends preferrably around the footing steel, and it grabs the footing and ties it to the pier.

[MountainDon]

So there, keep the rebar in piers and columns and footers and such.

The fibermesh sounds like an ideal concrete additive for use in a slab floor that was to be finished using a concrete stain process.

[glenn kangiser]

I agree with Don P.

For a while some engineers eliminated a lot of the steel in slab work but for the most part I see steel in the slabs now along with fibermesh sometimes.

I would use the steel myself in piers.

I do use fibermesh in stucco and the Kern/CBRI floor John and I reported on.

[Bobmarlon]

You don't need rebar in a regular foundation wall at least around here but Its highly recommended and Pretty much anything thats engineered there goanna want you to add rebar.

[glenn kangiser]

Footings here under a continuous foundation wall require 2 #4s continuous if nothing else.  Nothing in the wall itself though.