Concrete Chairs

[paulsharvey]

Quick scan of Google (after weeding through the manufacturers of the fiberglass rebar) seems to be; for what I would call typical use case (not power plants, not MRI rooms)
major advantages; light weight; corrosion resistance
Major disadvantage; can't do field bends; some talk about cheap fiberglass using inferior resins, that degrade in alkaline environment(ie concrete); and it failing when exposed to multiple fatigue loads.

When you look at the relative low cost of rebar compared to total project cost, at this time, I would run uncoated steel, Grade 60, unless you had a special use case or a special shipping issue with the weight.

The epoxy coated, it seems, can be worse than uncoated, as once the epoxy starts to separate, the bars aren't really bonded to the concrete.

 

[paulsharvey]

BTW, I remember hearing about fiberglass rebar the first time about 20 years ago, but it was specifically used in high energy environments, where there was a concern about steel rebar carrying voltage.

Construction is often slow to pick up on drastic changes at times. Had a company owner talking to another client company owner; he said we know the products, and we can build/make money with existing, and we don't want to be guinea pigs try new. His specific case he mentioned that red, salt treated, fire resistant roof trusses; that 5-10 years later, they found dissolved nails... another case was Hardi Pipe storm drain pipe. It's lighter than concrete, same price, longer joints, what's not too love; but it turned out it cracks under vibration over the years; and apparently lab tests didn't reveil it, till many miles of it was installed under roadways.

Right now, there seems to be a moving debate about HDPE vs FPVC for directional drilled pipe; and some municipalities love FPVC (common fittings with C900 PVC) and others refuse to allow it (claim when a joint splits, it's the entire 40 ft section).

 

[etpm]

When I had my machine shop built I had 2 foot high stem walls around the perimeter. I had to put 6 grade beams in that tied opposite stem walls together along the length of the building. Along with the rebar in the grade beams I also had fiber put in the concrete. I also had some more rebar put in the slab along with wire mesh. The wire mesh was 3/16" or 1/4". When the rebar and wire mesh was placed the crew used rocks to hold it above the ground. I was assured that this was OK. I have no idea if it was or not. We have so many rocks here it was easy for the crew to find plenty of rocks of the proper size. The slab is 7 inches minimum thick. I did this because of the heavy small footprint machine tools that were to be placed in the shop. There a few tiny cracks in the slab so apparently something was done correctly because there are no big cracks and the shop has been through one earthquake with machine tools in place.
Eric

 

[paulsharvey]

Attached is the standard plans detail on a P5 inlet top. The amount of rebar in those in huge.

 

[Streetcar]

Is fiberglass rebar a good thing or something to avoid? I've never used it, but Menards sells it for less than steel.

Not sure what Menards sells but cost is reason fiberglass reinforcement is not used more.

 

[4570Man]

Is fiberglass rebar a good thing or something to avoid? I've never used it, but Menards sells it for less than steel.

There’s not a Menards available locally buy the Lowes rebar is high. I can get it from other suppliers for close to half price. I’ve never used the fiberglass rebar but I’m not sold in the idea. We all know what happens when you cut fiberglass. I don’t want covered in that dust. You can’t bend it either which is a pretty big downside.

 

[Egon]

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I have a dumb question: if the rebar is supposed to be in the lower 1/3 of the slab why are the chairs or dobies 2.5-3" high when most slabs for non industrial use are in the 4-5" range?

There is a minimum clearance to the edge of the slab.

 

[Wood_Butcher_Dav]

This is what an homeowner can do, by following Eddie's advise.
Side note what motivated me to build this a few years ago - an above ground storm shelter with a 4 car garage was all of Mr. Walker's posting. Building the lake and all of his challenges like the dozer fixes.
Can't find the garage floor photos - 2" 4x8 foam boards, rebar on plastic chairs sitting on form board 600 feet of 1/2 pex tubing attached to rebar on 3 loops for a 28X40 5 inch pour.