billconner
Well-known member
I see Owens Corning has introduced Pink Rebar, fiberglass rebar. At Lowe's, same as price as steel. Nice to have options.
Pink rebar
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nadogail
Well-known member
My guess is that it wont rust. Am I correct?
txvwnut
Well-known member
Wonder what it looks like after you cut it with bolt cutters.
K'ledgeBldr
Well-known member
Yes, it’s an alternative to raw steel rebar- no rust!
But, there’s also “coated” steel rebar- so I guess it’s just a matter of cost and what engineer(s) spec for a specific duty.
But, there’s also “coated” steel rebar- so I guess it’s just a matter of cost and what engineer(s) spec for a specific duty.
Probably not the approved method, but I bet an abrasive cut off saw works well. Plus you get the benefit of fiberglass dust floating in the air.
OP
billconner
Well-known member
Non metallic rebar isn't new, but I had not seen it in big box stores or seen it competitive with steel.
WillyBoy
Well-known member
My first thought is, what happens when it's bent into a nice smooth 90 degree sweep and you let go of it?
I think it's unlikely that it will stay bent, and more likely that it will go "WHAP" and smack someone in the head when it straightens out.
I think it's unlikely that it will stay bent, and more likely that it will go "WHAP" and smack someone in the head when it straightens out.
OP
billconner
Well-known member
Lots of applications that don't need bending. Raises the question can you mix it with steel rebar? I'd guess it's OK but don't know.
HoosierBuddy
Well-known member
I was at a corrosion seminar at Purdue years ago, and the professor leading the class got pretty animated about a parking garage replacement on campus. The rebar in the decks had corroded causing spalling of concrete, to the point they were replacing the whole structure.
His concern was they were building the new garage to the the same spec with the same concrete and rebar as the failed garage. Sounds like non-metallic might be the way to go if it works.
His concern was they were building the new garage to the the same spec with the same concrete and rebar as the failed garage. Sounds like non-metallic might be the way to go if it works.
mike93lx
ALLIANCE MEMBER
Parking garages with metal rebar exist all over the place without issue. Not saying that fiberglas is a bad idea, but metal can work fine
mike93lx
ALLIANCE MEMBER
Huh?
larry4406
Well-known member
I've been on jobs where the concrete guy pounded u-shaped stirrups of metal rebar into the earth to then support the footing rebar. Third party inspector made them remove all the bars in the earth as he said they would lead to corrosion that would migrate inward; wanted all steel fully concrete encased.
Doubt a 20' continuous fiberglass rebar will suffice as a UFER!
mike93lx
ALLIANCE MEMBER
I get not putting rebar in the ground, but that is not the only application for FG barI've been on jobs where the concrete guy pounded u-shaped stirrups of metal rebar into the earth to then support the footing rebar. Third party inspector made them remove all the bars in the earth as he said they would lead to corrosion that would migrate inward; wanted all steel fully concrete encased.
Doubt a 20' continuous fiberglass rebar will suffice as a UFER!
larry4406
Well-known member
I thought you were challenging @bb29520 's comment; the fiberglass pounded into the earth might work as a standoff to then tie metal bars to. Not sure if water will wick up fiberglass from earth contact to then corrode the encased steel bars.
mike93lx
ALLIANCE MEMBER
I am challenging that pounding it into the ground is its purpose. That may be a use, but it isn't what it was designed for
ConCretin
Well-known member
If straight lengths of fiberglass bar are comparable in cost to steel rebar, it probably makes a lot of sense. It's lighter and thus easier to handle but I doubt the average garage would benefit from it's corrosion resistance enough to justify much additional cost. If the concrete is sound, it provides more than enough corrosion protection to protect the steel. When rebar corrodes, it usually means the concrete has already failed and it just makes a bad problem a little worse.
Any cost savings quickly disappear in more complex structures that require bent bars such as hooks or stirrups. You obviously can't bend it - the manufacturer needs to form it into the shapes you need. The cost might be justified in a parking garage or bridge deck where maintenance is challenging and corrosion is a major concern but I suspect good old rebar will continue to be common.
As an aside, I've always thought it was a little silly to worry about non structural rebar in contact with soil. I doubt water is going to wick up the offending bar and rust out all the other bar. You obviously want proper concrete cover around the main rebar but of all the potential concerns, a few pieces of rebar driven into the soil isn't very high up the list.
Any cost savings quickly disappear in more complex structures that require bent bars such as hooks or stirrups. You obviously can't bend it - the manufacturer needs to form it into the shapes you need. The cost might be justified in a parking garage or bridge deck where maintenance is challenging and corrosion is a major concern but I suspect good old rebar will continue to be common.
As an aside, I've always thought it was a little silly to worry about non structural rebar in contact with soil. I doubt water is going to wick up the offending bar and rust out all the other bar. You obviously want proper concrete cover around the main rebar but of all the potential concerns, a few pieces of rebar driven into the soil isn't very high up the list.
composite rebar has been around a long time and lately GRP has been upstaged by BRP (Basalt Reinforced) that considerably outperforms glass. For both types, however, you have to order bent sections from factory, same with rings. Just to put things into perspective: Basalt rebar is something like 8x the strength/weight ratio of steel. You can easily replace 1/2" steel with 3/8" basalt and have a much stronger, much lighter and totally corrosion free structure. Also same coefficient of thermal expansion as concrete.
hans109h
Well-known member
I once drove a couple hundred miles to buy some 1/2" x 12' fiberglass rod (think thick driveway markers) for the purpose of using it as the support structure for an amateur radio antenna. It was exactly what I needed and not that expensive, but impossible to source locally in the length I needed, so I went to the manufacturer. They didn't get many small orders, and their market for these lengths were as tornado and hurricane proof seeding/tree supports.
I'm going to have to take a look at this fiberglass rebar the next time I'm at Menards and see how it compares. It's always good to know what raw or semi-raw materials are available at the yard for repurposing. Thanks for sharing.
Hans
I'm going to have to take a look at this fiberglass rebar the next time I'm at Menards and see how it compares. It's always good to know what raw or semi-raw materials are available at the yard for repurposing. Thanks for sharing.
Hans
firebirdparts
Well-known member
I am curious about something related - if you pour concrete at freezing temperatures with rock salt in it, does that affect the rebar corrosion? My shop has a beautiful slab on the second floor which contains salt, but it can never rain on this floor. It's 20 years old, and it's pretty obvious already it's okay, but I have always wondered about that. Up north, in a parking garage, you are importing salt all the time, so you don't necessary see the difference.
Around here parking structures are lucky to last 40 years and bridge decks 20. Here in the prairies we are considered "low salt" winter roads!
paredown
Well-known member
Very cool--this is my new nugget of information for the day...
There's a pretty good general summary about this material here: https://www.basalt-rebar.com/
If you (or anyone else on GJ) wants to make far better concrete, you can buy made in USA stuff here: https://www.fiberglassrebar.us/basalt-rebar/ Nick (the guy in your link) is a wealth of knowledge and experience but the guys over in TX are the ones who got it into the marketplace by using existing rules (meant for glass fiber - that they also make) to test and accept under same standards when using basalt fiber. There is another company on the East Coast that sells out of FL who draw their own fiber offshore and are trying to do that inside of USA. Bright future for bonded tendon construction.
yatg
Well-known member
That's the whole deal with the concrete/construction/civil eng world - put steel rebar bonded tendons into your work and it pretty much guarantees you a complete replacement in 40 or 50 years. Concrete made with Portland Cement will shrink forever but the steel embedded in it wont. Eventually, micro cracks feed moisture to the steel, that then corrodes and the exfoliating oxide cracks the concrete some more.
The steel rebar can be coated - sometimes works, usually not for long - or you can go to stainless (******** expensive) or composite. Problem is the glass in fiberglass doesn't necessarily like the alkali environment - so the smart money for bonded tendons is basalt fiber bars. Far stronger than e glass (around S glass strength) but completely inert and same coefficient of thermal expansion as concrete. MUCH stronger, lighter and longer lasting that steel, but in the end any bonded tendon is going to get squished by concrete contracting.
Problem with composite rebar is as noted above - can't be field bent. You have to order the bends done at factory before curing or splice bends into straights.
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y'sguy
Well-known member
difficult to weld! haha
MovingAlong
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MovingAlong
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micromind
Well-known member
I wonder if you'd still need to attach the electrical UFFER ground to it.............
rlitman
Well-known member
You can attach the plastic ground wire to either the pinkbar, or your PEX water main.
edit: does hot melt glue count as a CAD weld?
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reader2580
Well-known member
A section of interstate freeway in the Minneapolis area was rebuilt with stainless rebar and other corrosion resistant technologies. The highway is supposed to last 70 years. The thing is, they already had to do the same twenty year concrete repairs to that section of highway that all concrete highways seem to need in Minnesota.
reader2580
Well-known member
The concrete contractor who redid my detached garage apron, and did the slab for my new garage, used composite rebar. Composite rebar is his standard unless there is a reason to use steel rebar.
Most of that is now e-glass. There is a TX company making basalt bar alongside their glass line, but mostly a lack of fiber production capacity in USA severely limits basalt (a far, far better fiber) in our market. There are plans (read bux) in place to fix that problem.
pcmeiners
Well-known member
Yes if the work is done properly, as in work done in the 1930s. Today's workmanship is pitiful unless carefully supervised, especially concrete work.
Basalt, interesting.
Be aware that fiberglass rebar, and for that matter basalt rebar, has much different engineering properties than grade 60 steel rebar. These bars are not interchangeable based on equal strength or area. The required bar area in your garage foundation slab is usually based on crack serviceability performance, and is largely a function of bar stiffness. The fiberglass and basalt bars are 1/3rd the stiffness of the steel bars per same area. Flexural design of reinforced concrete using fiberglass, basalt, carbon fiber, stainless, or mild steel bars has to be done on a case-by-case basis. All the properties have to be taken into consideration including strength, stiffness, ductiltity, fatigue life, creep and relaxation, development length and bond, coefficient of thermal expansion, cost, and durability. Grade 60 rebar is a natural match for reinforced concrete, and is still easily the best choice in most all cases.
Corrosion of steel rebar is usually an indication of poor concrete. Just look at a good bridge deck concrete, which is nothing special and inexpensive. It takes between 125 and 350 years for chlorides to penetrate 2.5" of cover to reach the rebar and start corrosion in a modern bridge deck. The bridge deck concrete has about 600 Lbs of cementitious material, with 80/20 portland cement to Type F flyash or 50/50 portland cement to slag. The water/cementitious ratio is 0.45 or a little less. It is cast at about 5" slump on cross slope using water reducing admixture for workability. It is fogged until initial set, then covered. After final set it is moist cured and covered for 7 days, then left covered. They also can opt to use a spray on curing membrane early in the process. The use of epoxy coated, stainless, and non-ferrous rebar is solving a problem that we do not have in most design cases.
Corrosion of steel rebar is usually an indication of poor concrete. Just look at a good bridge deck concrete, which is nothing special and inexpensive. It takes between 125 and 350 years for chlorides to penetrate 2.5" of cover to reach the rebar and start corrosion in a modern bridge deck. The bridge deck concrete has about 600 Lbs of cementitious material, with 80/20 portland cement to Type F flyash or 50/50 portland cement to slag. The water/cementitious ratio is 0.45 or a little less. It is cast at about 5" slump on cross slope using water reducing admixture for workability. It is fogged until initial set, then covered. After final set it is moist cured and covered for 7 days, then left covered. They also can opt to use a spray on curing membrane early in the process. The use of epoxy coated, stainless, and non-ferrous rebar is solving a problem that we do not have in most design cases.
coef thermal exp x 10to-6/degF A615=
yield strength KSI: Grade 40 steel rebar = 40ksi E glass bar basalt bar
grade 60 steel rebar = 60ksi
I would argue that is not the case, as both Florida and Quebec have banned coated rebar. Some studies show epoxy coated steel actually corrodes faster than bare steel.
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All the properties have to be taken into consideration including strength, stiffness, ductility, fatigue life, creep and relaxation, development length and bond, coefficient of thermal expansion, cost, and durability.
One failure mechanism is indeed the difference in thermal expansion coefficient between concrete and steel. E glass closer but basalt almost a perfect match
You call materials with VERY different coefficients of thermal expansion and difference in dimension over time giving a guarantee of failure in tension from the concrete matrix a "natural match"?
As I am sure you actually know but for some reason do not want to deal with is that the route of water into the rebar to corrode quickly is a function of the dimensional incompatibility of concrete vs. steel that WILL result in compressive failure due to poor modulus of elasticity of the matrix. It is easy to make relatively impervious concrete mixes and coatings, but clearly from the real world a lot more difficult to make a self-healing crack.
I am not saying every use of steel is bad - as there are some things (i.e. guaranteed failure of columns from geophysical movement where the plastic behaviour of steel rebar crushes the occupants more slowly) but when designing things you don't want to fail, composite bonded tendons - particularly basalt - offer some clear advantages. Similarly steel cable works very well for post tensioned slabs - but hardly cost effective for most home garages.
reader2580
Well-known member
I'm trying to figure out where this is that concrete highway bridges last 125 to 350 years. The Minnesota Deportment of Transportation routinely replaces interstate overpasses and underpasses at 40 to 60 years. New major bridges crossing bodies of water generally have a 100 year design life. Those bridges that aren't replaced at 40 years will generally have a deck replacement and rehab done by 40 years. MNDOT is starting a major two year bridge rehab program on I-394 where the bridges are just less than 35 years old.
We'll see how long the bridge decks last that were built in the last 20-30 years since the DOTs improved their concrete specifications. Some of the DOTs have gone to stainless or semi-stainless rebar for bridge decks and aggressive environments, and to carbon fiber or stainless prestressing strands. We should be able to get 75-100 years out of a new bridge deck, but the decks take a lot of abuse over that time period. Also, girder spacing has widened in recent years putting more demand on the decks, and thickness remains at 9". Even at that, I have inspected numerous bridge decks without a single crack, except a couple over the piers, after years of service (they are designed to crack in flexure).
Research has shown that mild steel rebar durability in concrete exposed to chlorides is the same in uncracked concrete and in concrete with cracks less than 0.004" wide. But cracks can end up wider than that in bridge decks for several reasons. I have tried to introduce partially-prestressed bridge deck design to DOTs but nobody is biting (cracks are held closed except during truck live load events). Crack widths are controlled as part of typical design by using the correct rebar area and size. GFRP rebars hinder this effort since they are 1/4th the elastic modulus of steel, and they creep. That said, I inspected a bridge deck with GFRP rebar after 2 years of service and there was not a single crack anywhere (simple span bridge). Of course the decks on the two spans next to it with steel rebar were not cracked either. This is on a steel girder bridge no less. It rained every day for two months after these decks were cast.
And steel and concrete have nearly the same coefficient of thermal expansion. CTE in concrete varies with aggregate type, so BFRP can never be an exact CTE match either. xFRP is made from two materials with radically different CTE, so CTE of 6E-6 is designed into BFRP. From that we get low modulus and significant creep. The carbon fiber CFRP prestressing strand has a CTE 1/10th that of concrete. It has a modulus 3/4 that of steel, and relaxation only about 4 times that of steel prestressing strand. So temperature change is an important load case, and girders can be cracked easily in fabrication if you let the concrete cool off before cutdown of prestessing strands. But it works well, and is expensive.
Since garage slab reinforcement is about crack control, I would opt for steel rebar and a good mix design and curing. If the slab gets salted, then maybe MMFX steel bars could be used or xFRP bars in greater number.
Research has shown that mild steel rebar durability in concrete exposed to chlorides is the same in uncracked concrete and in concrete with cracks less than 0.004" wide. But cracks can end up wider than that in bridge decks for several reasons. I have tried to introduce partially-prestressed bridge deck design to DOTs but nobody is biting (cracks are held closed except during truck live load events). Crack widths are controlled as part of typical design by using the correct rebar area and size. GFRP rebars hinder this effort since they are 1/4th the elastic modulus of steel, and they creep. That said, I inspected a bridge deck with GFRP rebar after 2 years of service and there was not a single crack anywhere (simple span bridge). Of course the decks on the two spans next to it with steel rebar were not cracked either. This is on a steel girder bridge no less. It rained every day for two months after these decks were cast.
And steel and concrete have nearly the same coefficient of thermal expansion. CTE in concrete varies with aggregate type, so BFRP can never be an exact CTE match either. xFRP is made from two materials with radically different CTE, so CTE of 6E-6 is designed into BFRP. From that we get low modulus and significant creep. The carbon fiber CFRP prestressing strand has a CTE 1/10th that of concrete. It has a modulus 3/4 that of steel, and relaxation only about 4 times that of steel prestressing strand. So temperature change is an important load case, and girders can be cracked easily in fabrication if you let the concrete cool off before cutdown of prestessing strands. But it works well, and is expensive.
Since garage slab reinforcement is about crack control, I would opt for steel rebar and a good mix design and curing. If the slab gets salted, then maybe MMFX steel bars could be used or xFRP bars in greater number.
logical
Well-known member
That must be a pretty big garage that some of you are suggesting both a suspension bridge and a concrete overpass.