Rusty Rebar?!?

[Sheepdogmarine]

Okay, a totally newbie question, but you know what they say about then one never asked.

Can you use rusty rebar? Not horrible, but the surface is covered.

This would be for my slab. I can get 1000 lbs or so for free so I figure if it would work, why not?

Did I mention I am on a budget?

 

[Photo]

I'd be very careful about using it unless you can get it sandblasted or spend a lot of time wirebrushing the rust off of it.

The rust is a sign that it's been wet. The rust will continue to build up on the rebar in the concrete, as it builds up it will expand eventually cracking the concrete. Not sure where you live in Maryland, but have you ever seen exposed rebar in a semi-tropical or tropical environment? Wherever it's been exposed to salty sea air, the rebar does not last long at all. Or even rebar in a bridge deck or column that's been exposed to salt for clearing roads. Yes, the salt does a lot of the damage, but you are already starting with rebar that's been compromised.

Talk to an experienced concrete contractor and get his opinion. If it was me, I don't think I'd do it. Rebar is not that expensive compared to the cost of the concrete you're trying to pour.

Lane

 

[red]

Almost all the rebar I've seen has rust on it. The green coated rebar is to keep the road salt from reacting chemically with the rebar and ruining the concrete. I would use it. On my garage I coated my rebar (with rust and @$6 a piece) with the Rust-Oleum Cold Galvanizing Compound. Free is good!

Ed

 

[Mike83]

I disagree that you should not use it. Rebar will start forming surface rust the second it is made. Take a look at buildings and bridges as they are built - the uncoated rebar is red and brown with rust. In fact, the rust provides better engagement with the concrete for structural members. The key to longevity is to seal the concrete to avoid chlorides from attacking the reinforcement. If you get a crack in the slab and salt water gets in there, you will have ongoing problems.

Think about this - bridge decks built with black steel and having only about 2" of concrete cover on top of them will last 15-20 years before rehab, and a total expected life of 40 years.

 

[Sheepdogmarine]

Well here is a picture. Maybe that will make a difference.

View media item 3062

 

[Gary S]

I've put it in rusty before and never had a problem. And, I've cut out 30-40 year old rebar and it was still rusty and doing its job.

 

[PurdueSD]

I'd be very careful about using it unless you can get it sandblasted or spend a lot of time wirebrushing the rust off of it.

The rust is a sign that it's been wet. The rust will continue to build up on the rebar in the concrete, as it builds up it will expand eventually cracking the concrete. Not sure where you live in Maryland, but have you ever seen exposed rebar in a semi-tropical or tropical environment? Wherever it's been exposed to salty sea air, the rebar does not last long at all. Or even rebar in a bridge deck or column that's been exposed to salt for clearing roads. Yes, the salt does a lot of the damage, but you are already starting with rebar that's been compromised.

Talk to an experienced concrete contractor and get his opinion. If it was me, I don't think I'd do it. Rebar is not that expensive compared to the cost of the concrete you're trying to pour.

Lane

Ignore this guy....

It is bare steel from the factory, not sure where he got his information- but he is wrong... Use away, even new rebar is usually stored outside and already starting to rust.

Jeez....

 

[red]

Rusty rebar may be a problem in exterior work were it would be exposed to salt and moisture. Are you sealing your garage floor? Are you installing plastic under your concrete slab? Both would stop/slow down any chemical reaction with the rebar.

Ed

 

[uhcrandy]

I have got new rebar from the supplier that looked like that. Thats not so bad. Once it starts to expand or flake from rust, thats a different story.

 

[caper]

Well here is a picture. Maybe that will make a difference.

View media item 3062

Looks like the new rebar in most steel yards I've seen around here.

 

[BackAgain]

I didn't know you could buy rebar without rust?

 

[X1 Mike]

I'm with the general concensus, I've never seen rebar that wasn't rusty. Most yards will store it outside in the elements.

 

[toxicz28]

Looks fine to me.
I've used worse.

 

[Art From De Leon]

As long as there is not loose, flaky rust, the concrete will bond to it better than a smooth, or painted surface.

 

[Charles (in GA)]

Do NOT weld rebar and then put the welded joint in the concrete, that is not allowed by building codes. Virtually all rebar has that thin film of rust on it. If that is all, you are looking at normal rebar. If it has heavy flakey rust, sell it for scrap metal.

I watched a TV documentary about ship breakers in India. They buy old Russian ships and tow them to India where they beach them and cut them up. The steel plate is cut into large chunks and run thru a mill where it is sliced into strips and then run thru a furnace and rolling forms and it comes out as rebar. I always tell people that their rebar is made from old Russian ships, no one understands of course.

Charles

 

[Sheepdogmarine]

Well everyone made me feel better. I think I will use it.

Thanks!

 

[Sheepdogmarine]

Do NOT weld rebar and then put the welded joint in the concrete, that is not allowed by building codes. Virtually all rebar has that thin film of rust on it. If that is all, you are looking at normal rebar. If it has heavy flakey rust, sell it for scrap metal.

I watched a TV documentary about ship breakers in India. They buy old Russian ships and tow them to India where they beach them and cut them up. The steel plate is cut into large chunks and run thru a mill where it is sliced into strips and then run thru a furnace and rolling forms and it comes out as rebar. I always tell people that their rebar is made from old Russian ships, no one understands of course.

Charles

Well, now I understand. That is pretty cool.

 

[timewarp]

That's just light surface rust, no problem using that rebar.

 

[GeorgiaHybrid]

The rust is normal and helps promote adhesion to the concrete. That is why any steel in contact with concrete is not painted (curb plate, beam flanges, embed plates, etc.).

 

[brownbagg]

I,m a concrete inspector, rusted rebar is legal, as long as you knock the scales off it.

I would not think twice of not using it

 

[BackAgain]

I watched a TV documentary about ship breakers in India. They buy old Russian ships and tow them to India where they beach them and cut them up. The steel plate is cut into large chunks and run thru a mill where it is sliced into strips and then run thru a furnace and rolling forms and it comes out as rebar. I always tell people that their rebar is made from old Russian ships, no one understands of course.

Charles

They do the same thing here in America, except they use expensive and often irreplaceable/historic firearms as the source for steel. All the guns police departments confiscate...all the guns morons turn in for a free $50 gift certificate somewhere...usually someone from the police department watches them get melted.

They could just sell them to law abiding citizens or use them for their own arsenal, but that would make too much sense....

 

[austin308]

Well I was a Public Works inspector for several years and have inspected thousands of yards of concrete. The answer is (the rust can not be to the point to effect the deformation in the steel). That is what grips it to the comcrete. Your rebar is fine. use proper rebar chairs, moisture barrier, and not to high slump concrete these will make your project stand the test of time. Hope that helps

 

[Dan in Pasadena]

Ha, ha...I THINK this may be a subject on which I qualify as somewhat of an expert on. I am the Construction Quality Manager for the METRO system in Los Angeles. We just finished the Gold Line Eastside Extension and I am now managing construction quality for the I-405 Sepulveda Pass Widening project we're doing for CalTrans.

Listen to the guys that tell you there is NOTHING to worry about with surface rust on rebar. In fact, I will have to find it but there is actually a technical position paper issued by the ACI, American Concerete Institute that says the bond between concrete nd rebar is actually improved by mild rust. Trust me, you're fine. Not to worry.

 

[krooser]

I used to haul rebar out of the steel mills in Gary, IN... it sat outside for weeks/months until it was shipped... rusty as hell.

 

[A_Pmech]

In fact, I will have to find it but there is actually a technical position paper issued by the ACI, American Concerete Institute that says the bond between concrete nd rebar is actually improved by mild rust. Trust me, you're fine. Not to worry.

Dan, I'm interested in reading that paper.

 

[Dan in Pasadena]

The more I think about it, it MAY have been AISC that issued that paper. I'll look up the source when I'm back in the office - taking tomorrow off to go camping this weekend. When I find it, I'll post it or a link.

 

[Snap50]

Well here is a picture. Maybe that will make a difference.

View media item 3062

That's fine. The rebar on most jobs look like that. It's just light surface rust.

Don't paint it like someone noted. The rebar needs to bond and the paint, if not well bonded will hinder that.

The "green" coated rebar is actually epoxy coated, but the kicker is that if you cut it then you end up with bar steel where rust can start, so you defeated the purpose. Also the epoxy coated bars require MUCH longer embedment length to achieve the same bond as the black (bare) bars; and that also reflects on the bars that someone painted. Longer required embedment meaans longer lap lengths to achieve continuity.

As long as it has the proper amount of minimum concrete cover, once it's in the concrete it's not going to see moisture to rust it as long as it is not an exterior slab.

 

[A_Pmech]

The more I think about it, it MAY have been AISC that issued that paper. I'll look up the source when I'm back in the office - taking tomorrow off to go camping this weekend. When I find it, I'll post it or a link.

Cool.

Looking forward to reading it.

 

[tatra]

well i disagree and think it should be blasted clean, powder coated and pin stiripped on the ridges then cleared and polished by 21 year old swedish virgins..........tie wires are to be galvanized dipped and twited no more than 3.3333 turns.........anymore, fire the guy doing the twisting.........support all rebar with cast steel blocks machined to specific dimensions as required to aqllow for an aestehically pleasing look..........remember beauty is skin deep and only you will know how good your rebar is and that's all that counts........

 

[hetkind]

I have been on many jobs were welding rebar is REQUIRED...it is essential in blast resistant structures to weld and not tie the rebar together.

Howard

 

[ebfabman]

No welded rebar joints in concrete??? What is the reason for this? Other than just its code....if it is....I'm not saying its not, cause I donno, but I'd sure be interested in knowing whats wrong with welded rebar imbedded in concrete.

 

[Daniel Dudley]

No welded rebar joints in concrete??? What is the reason for this? Other than just its code....if it is....I'm not saying its not, cause I donno, but I'd sure be interested in knowing whats wrong with welded rebar imbedded in concrete.

I believe that rebar is supposed to be overlapped 18 inches where it joins, and some people don't like to see it wired together tight at the overlap, they like to see space around the bars so that each bar can be totally encased in concrete. YYou don't see that much though.

I would think the overlap would be better than a weld in general, as well as quicker and easier. I like rebar, and I like a lot of it. I like to see it in the bottom third of the pour, and I like to see it bent up into walls, or candy caned down into pours. I like to bend around corners, and run the overlaps on the straight runs.

It was very good to hear from an inspector, among others.

 

[brownbagg]

rebar is really not a strong metal, so welding will make the metal brittle. Most of rebar is in tension mode so the pulling of the bars could "pop" under loads.

Now there is some welding of rebar that legal but its under strict guidelines.

 

[viper86]

standard ASTM A615 rebar is not weldable (it is, but the weld quality is poor and therefore prohibited), but ASTM A706 rebar is. The only welding on reinforcing I see or spec is for embed plates in concrete. We don't do anything special enough with concrete to warrant it otherwise.

I have seen rebar in varying degrees of corrosion, from almost none to almost completely covered. I can't say I've seen a sheet of wire mesh that wasn't rusty, though... though I was probably chewing out the contractor for "pulling up" the mesh and not placing it on chairs prior to concrete placement and not paying attention to the corrosion on the mesh

 

[bazzateer]

In fact ..................... there is actually a technical position paper issued by the ACI, American Concerete Institute that says the bond between concrete nd rebar is actually improved by mild rust.

Stands to reason really, the surface rust introduces small 'pits' which increase the available surface area for the concrete to adhere to and 'grab' the rebar. It's the same principle when you key a surface to enable paint to adhere better.

 

[bazzateer]

Just realised, "Rusty Rebar" - I'm sure I've seen some of his films!

 

[Sheepdogmarine]

well i disagree and think it should be blasted clean, powder coated and pin stiripped on the ridges then cleared and polished by 21 year old swedish virgins..........tie wires are to be galvanized dipped and twited no more than 3.3333 turns.........anymore, fire the guy doing the twisting.........support all rebar with cast steel blocks machined to specific dimensions as required to aqllow for an aestehically pleasing look..........remember beauty is skin deep and only you will know how good your rebar is and that's all that counts........

Actually, I just got it soda blasted and acid dipped. I am taking it to the chromer this morning. Can't wait to get it back!

Gotta have some bling!

 

[Mike83]

I believe that rebar is supposed to be overlapped 18 inches where it joins

18 inches would be an absolute minimum for #4s generally. I designed a retaining wall last month that lapped #8s at about 7 feet. Of course, these were coated bars and also experienced high tension. It all depends on the situation - coated or uncoated, ratio of area of steel provided to As min, size of bar. Lap lengths are classified as Class A, B or C. Generally Class C is specified as it is the most conservative (and requires less work than trying to check to see that the other lap lengths will be ok )

 

[Zrexxer]

rebar is really not a strong metal

There's another misinformed statement. Rebar is actually quite strong, medium carbon steel. The reason that heated bends/welding is not generally allowed practice is because of localized embrittlement in the heat affected zone due to its carbon content.

 

[mx5.7]

The "green" coated rebar is actually epoxy coated, but the kicker is that if you cut it then you end up with bar steel where rust can start, so you defeated the purpose.

That is why the supplier always sends a couple of cans of epoxy to mix together and coat the ends or do touch ups.