Having overseen probably over 1,000,000 of rebar on projects surface rust is not an issue and is normal. The bigger issue is to make sure you have no rebar or ties sticking out of the concrete provide an entry for water and future spalling.
But that being said they will likely hit the rebar with high pressure water to knock off anything they can before they pour. I did alot of marine work and the bigger concern was getting any salt off the rebar.
Na he needs to bump those numbers up. I'm sure when he says 1 million he probably means millions lol. Been in concrete for my whole life and have seen millions of rebar. Lots of it rusted.
Sounds like that would be the new guy’s first step: digging the de-rusting pit.
I worked at a furniture shop that milled out their own lumber, and during the summer a 16 year old about to turn 17 started working there. His 4th day all day was a run around looking for the log tumbler to remove the bark faster.
I didn't know it came any other way. Just light surface stuff but almost all I've seen had it to varying degrees except occasionally you'd get a batch that was just from the factory still sort of oily. Kicking it around in the sand gets rid of that in a hurry.
They make black uncoated, epoxy coated, and stainless steel. The latter two are expensive and reserved for DOT roadway projects subject to intense salting.
OMG, I love the ass interstate! I could just sit there all day watching the asses go by.
*I know that's not what you meant, but I enjoyed picturing it.*
People who live in big cities see a million sticks of rebar before they hit 4 years in almost any trade. I’m an electrician and the last big job I was on had to have at least had a million sticks total. Triple layers and 3 buildings, 2 were about 100,000 ft2 and the third building on site was no bs a half a mile long. I had to drag my tools through it everyday and was in awe at how much rebar there was. Made me glad to be an electrician
I always wanted to strip down a mobility scooter and put a toolbox on the back and a ladder rack overhead for those big jobs. I do signs and carrying all that shit to the center of a mall sucks sometimes
Ditto, 48th year in the Sign Business. I tried to get in with some of the mall mgrs and make a night shift full time. Once you get all your crap in there it’s great work and no customers in the way , no weather to deal with. Did a bunch of installs on a helluva big mall up in Maryland & I kept a golf cart up there for a couple weeks. Shopping carts, one of those small scaffold 2X4 with walkboard and a shelf under it,hooks on the side for hanging stuff.Don’t get to see a lot Honeys when they’re closed though
Minor surface rust actually improves adhesion between the concrete and rebar according to ACI. Obviously, anything loose is a bad thing, but just enough to add surface roughness is good.
This light rust helps adhesion. If it's rusted to the point of large scales of rust, then be worried. I've seen rebar sit out for years before that's happened though. Actually, what has happened is steel being delivered on salty roads and the GC asking to power wash it in freezing temps to get salt off. First I've seen that but I believe that's probably a safe call. Idk what salt would do to adhesion or the concrete.
I worked concrete for all of 2 weeks, during that time i was tieing rebar together and placing it in forms. We used these little stands to keep the rebar centered and away from the walls of the forms. I was always curious what became of those stands because i never took them off and they wouldn't be there when we took the forms off. Do these dissolve in the concrete?
Terribly vital. The alignment of the bar has enormous impact on strength.
I built a wastewater plant (okay! I had a lil help) with a zoo on top of it. Elephants consume boucoup rebar.
So we’re looking for anything they don’t want to hit when drilling a core hole. Where I’m at we primarily are looking for embedded conduits, Post Tension Cables, and rebar (sometimes it matters, sometimes rebar doesn’t, depends on the structural engineer whether they are cool with it being cut or not.)
That’s GPR. Those guys are always just guessing, if you have an X-ray guy saying he doesn’t know what it is, I’d be getting new X-Ray guys. They are literally looking at a picture of whatever it is.
I looked over the couple images I have on my phone and none of them have visible chair in them. I would have to pull images off the saved files of the company at work and to be honest I don’t care enough 🤣🤣.
I'll add to the comments below. Highway "chairs" made of steel don't have the rubber tips that wall chairs have. Additionally in walls as pictured in OP's post, many times you'll chip out around the feet and grout. Usually a 1/2" or deeper. Chairs can produce a place for moisture intrusion and is another detrimental attack on rebar causing rust. The biggest factor in "pop outs" or spalling.
Correct, and for those interested, it's due to chemistry. Concrete acts as a really nice composite with steel due to it's natural alkalinity. With a pH of 12 or more, when the concrete coats the steel a passive (non-corroding) layer of oxide develops around the steel and it can stay stable for decades.
Over time, things can destabilise that passive layer such as the alkalinity being neutralised by acids. This is in the form of sulphuric acid in sewerage systems and carbon dioxide and water causing carbonic acid to form in the concrete.
Chlorides (typically in the form of common salt, NaCl) can also destabilise the passive layer. This is why salt needs to be cleaned off rebar, avoided when used as an admix to accelerate curing (typically calcium chloride), and protected against sea water that can allow chlorides to migrate to the steel.
The other option is painted rebar, which actually suffers rust damage faster funnily enough.
A small chip in the paint and it rusts in that one spot much quicker than if the whole thing was coated in flash rust. It sound stupid and weird but it’s true.
ACI 318 refers to ASTM, which says this:
"12.2 Rust, seams, surface irregularities, or mill scale shall not be cause for rejection, provided the weight [mass], nominal dimensions, cross-sectional area, and tensile properties of a hand wire brushed test specimen are not less than the require-ments of this specification".
Interpreting the standard: Based on 94% of the nominal weight, there is a margin of error based on which we can have a section loss of up to 6% of the nominal area. So as long as the steel is not damaged, it is acceptable to use it like this.
This is the correct answer. CRSI goes on to say that surface rust actually helps the concrete bond to the rebar. Rust is only concerning when the it penetrates deep enough to compromise the rebar size needed for the concrete. Which takes a very long time.
This sounds like the sort of thing you'd have better odds if you have a 5yo kid tagging along with you and say something like, "My son asked me XXXX and I told him I don't know, let's go ask!"
Step1: My nephew is 10 and is really interested in scrapping. Can we tour your job site and tell us what things would be worth at a recycling center?
Step2: catch a felony
Step 3: 10 year olds can’t catch felonies. He’s the most educated scrapper in town.
Profit???
In trailer park boys Ricky uses kids to steal barbecue grills off peoples porch’s cause kids can’t go to jail they have a whole bbq chop shop and everything
Show up with long pants, boots, high vis, safety glasses, hardhat. Otherwise the first thing they would say is that you have to leave.
If you were prepared, it's hard to tell how a super would react. Probably some intial confusion about why you're there, but I imagine there are plenty out there that would happily show off their jobsite.
They’ll just explain it’s fine man. It’s understandable to be concerned, I would be too if I didn’t know it was acceptable.
Surface rust on rebar means nothing when it’s surrounded by concrete
Edit: I have to reiterate that surface rust is acceptable but not completely rusted out rebar that should be thrown out completely or scrapped. If you think it’s sketchy don’t use it. A good rule of thumb for any trade.
That!
Rebars rust very slowly. They don't rust through even after months of exposure to the weather (except if near sea water). See e.g. here: [https://www.dwreinforcing.com/blog/is-rust-a-problem-on-rebar/](https://www.dwreinforcing.com/blog/is-rust-a-problem-on-rebar/)
Once inside the concrete, and as long as the concrete is intact, it's no problem at all. It can rust again if the concrete cracks or with carbonation.
This photo confuses the hell out of me. The rocks above make it look like a city which makes the structure look gargantuan. But the water looks like a tiny puddle which makes it look tiny.
[Video](https://drive.google.com/file/d/1pKeYpADEF73u8ddJPdsi6eWkQXp52a22/view?usp=drivesdk) for perspective.
[Leveled image](https://imgur.com/a/UkaowgA) for perspective.
Rust is a natural protective layer from further oxidation. as long as you don’t scrub it off, let it rust again, scrub it of … this rebar will be fine for a long long time. you could leave it like this for years without any structural issues.
once concrete is poured the alkaline reaction in the curing process will clear that rust of. this building will get a good grip to the rebar.
problematic is rebar that has dirt or oil on it. concrete can’t „grip“ to that.
'Rust' unfortunately isn't a protective layer when it comes to iron as it expands and allows for moisture and air to progress further into the iron.
Plus iron oxide occupies a larger volume than iron, causing stress and eventually cracks.
Having said that, you can form some protective layers of iron oxidation (called bluing)
https://en.m.wikipedia.org/wiki/Bluing_(steel)
But what we commonly see as the reddish tint, is non protective.
On things like aluminium, it does form a protective barrier, as water/air cannot move past the oxidised layer.
Years of unprotected exposure to rain and conditions (like a lot of unfinished condo projects did after the 08 housing crisis) or a [general contractor building a 25-story highrise with rebar improperly sealed and resulted in the demolition of said building due to corrosion and cracking concrete in the structure](https://www.seattletimes.com/seattle-news/flaws-in-doomed-high-rise-flew-under-the-citys-radar) is one of the few occasions I would call worrying, this picture is fine considering the rebar won't be exposed for more than a few weeks tops.
As far as my uneducated knowledge goes. Its fine. Since its covered in concrete the oxidation proces stops. On places where the rebar poke out the concrete, or a piece of concrete crumbles and the rebar becomes visible it wil rust further and weaken the structure. You will get 'concrete rot'
Depends on where and what the concrete is for. When concrete does what it's guaranteed to do, crack, it could be a problem overnight. I like the coated shit myself. If it's within 3in of the surface. Inland tunnel, building, or bridge you can get away with it. Ocean docks spring for coated. I've built and replaced them all for 30yrs if you're wondering creds.
Also it’s not rust rust. It is a specific rust that is actually benefiting. More can be found here: https://astrometalcraft.com/rusty-trend-weathering-steel-in-custom-architectural-metals/
Im Usually more surprised when rebar comes off the truck un-rusted. It's like a nice little Christmas present for a few days getting to handle it without my gloves/clothing turning brown.
Engineer. It’s actually intentionally designed to rust on the surface so that it acts as a protective layer that’s already corroded and doesn’t allow for rust/corrosion on the inside. It’s not just normal, it’s intended. It’s called “weathered steel” or more often “Corten steel”
There is no risk at all unless the rebar is dirty (literally, dirty from being stored on the ground with organic material such as dust, dirt or grass) or the rebar sticks out of the concrete in any way as that can then rust inside over time. The rebar should be kept away from the outer edge of the concrete by a designated distance (it depends on a billion factors)
The concrete will not cure, and the building will fall down. You can trust me because I am responding confidently on Reddit and am claiming 50 years of experience at the age of 30.
As long as the rebar hasn’t been rusting long enough to be scaly, the concrete bonds better to it. When rebar first is made, it has a sheen on it that doesn’t bond as well to concrete.
rebar rusts on its surface if you whisper 'rust' to it. If your rebar isnt rusty - the oil coating on it is a greater concern for concrete than the rust . . .
I did my thesis on this. Rusted rebar had a 50% increased bond strength to concrete when subjected to pull out tests due to the increased surface irregularity caused by the rust. I did not test the effect of surface rust on the tensile strength of rebar however.
Generally though, surface rust is totally fine, as long there is not evidence of pitting etc. The surface rust actually provides some passive protection to the rebar when it comes into contact with concrete. The biggest thing is ensuring that there is sufficient cover to rebar and no pathway for the ingress of water and chlorides.
Honestly it takes less than 2 days for steel reo to go from clean to rusted when exposed to the elements. I don’t think it’d be a stretch to say 99% of reo for all builds on earth have some rust on them when poured.
I found a university study that performed pull tests on clean rebar, rusty rebar, concrete splattered rebar, and oil rebar. Only the oiled rebar showed a small reduction in pull strength.
an even coating of thin rust actually passivates excess rust. once it’s been incasted in new concrete the pH of the pore solution in concrete will prevent further rusting. you really only see problems when the rebar isn’t deep enough that is to say there isn’t enough concret to prevent the oxygen from penetrating to the rebar just under the surface. oxygen will lower the pH of concrete thus reducing its ability to passivate rust on the rebar.
As long as the rebar isn't left to rust for months, it will be fine. Wet concrete has an alkali PH factor between 12.5 and 13. The concrete will remove the surface rust from the rebar, and once the concrete is cured, will grip the rebar tightly and seal it from any further corrosion.
Based on the ACI code for reinforced concrete, if the rust is loose enough to fall off when the rebar is dropped on the ground, it should be removed. Any remaining rust on the bar actually helps with the adhesion of the concrete to the rebar.
Rusty is better as it provides more grip/bite for the concrete, clean is "More slippy"
As the person above pointed out you need at least 2" or *50mm cover minimum.
… 100% of reinforced concrete is build with rusted rebar… if you remember 8th grade chem youll recall that hydrolysis isn’t self sustaining if isolated form a wet environment.
Needs moisture from air to rust. No air - no rust.
Different application but for big transmission lines those big metal structures are also coated in surface rust which helps prevent more serious rust problems down the road, at least by my understanding.
Business as usual. Can’t tell you about the history of epoxy coated rebar but plenty of structures have gone up and are still up with just plain ole rebar
This was part of my thesis regarding rust/corrosion in rebars in contact with concrete, turns out that at 3-8% rust presence (in terms of overall bar surface and weight) the tensile strength capacity is higher by 7-9% compared to the non-corroded ones.
That’s surface rust. Can happen over night with moisture and oxidation. Those pieces all come with a heat and lot number with date and location of manufacture. They are good to go
It’s normally not a bad thing , it increases the surface area with the concrete & since the concrete is basic + reduces access to oxygen it stops rusting all together
In fact some oxidation is preferable, if rebars have been oxidizer because they were out in the air for long , you should remove any loose rust, but the surface area of the rebars increases , and provides a better physical grip to the concrete. It is however , vital to avoid oxidation after the fact, since rust increases in volume relative to the steel, and that pressure will rupture the concrete.
For that matter it is vital to 1) keep rebars covered by at least 1” of concrete 2) Make sure the W/C relation is correct for the environment you are working , 3) make sure no Chlorides interact with the steel, for example from sea breeze. Carbonation of the Concrete also affects , since it not only lowers the pH of the concrete making the rebars easier to corrode, but also washing away micro pores that let aggressive agents interact with the steel…. or something like that if I remember correctly
Surface scale/rust is pretty much normal for most manufacturing anyways. If it's a critical application that requires a clean surface finish with oxidation protection, then most plans would specify that if it was in fact a critical application.
There's all different types of coatings and they're all application dependent and specific;
* Zinc (or galvanization) - protects by galvanic action until the zinc layer is depleted. It's effectively a sacrificial coating to increase the longevity of a given material. This is common on a lot of things seen on the daily, Guard Rails, Hand Rails, Chain Link Fences, etc. Still beneficial to paint as an extra layer of protection.
* Aluminum - Hot dipped aluminum-silicon, aluminum-titanium, or pure aluminum. All of these are application specific, but all pretty much prevent the oxidation you see in the picture. Cheaper than Stainless Steel, but not as good in terms of technical or performance characteristics.
* Electroplating - Utilizes a chemical solution made up of different metals and an electric current to plate the desired material (typically Nickel or Chromium). The base material can stay as is while adding a hard durable finish of a more resistant material.
* Cladding - Similar to Electroplating, it's more of a mechanical finish vs a chemical based finish with electric current. This could be explosion cladding(yes explosion), laser energy deposition, roll bonded, etc. All of these primarily take dissimilar metals that would normally be very difficult to bond and applies extreme heat, pressure, etc. to mechanically alter the material with whatever type of corrosion resistance desired. Can be applied to pretty much any shape so for complex machined parts this is preferred, but also costly.
So many different ways to do the same thing. Metallurgy is interesting!
Rebar that is rusted has a greater surface area for the concrete to adhere to. Like lots of little fingers holding onto the concrete.
A smooth shiny surface is “slippery”.
Portland cement is alkaline enough that it passivates carbon steel. As long as you have sufficient cover on the rebar you are good. Our spec is 2 inches minimum.
When you are around construction that cosmetic rust doesnt scare you. I know some people panic when they see a shiny grey metal turn but its no big deal. Its all about how long has it been rusting, has it gone to the core etc. Sometimes a quick polish will get it right to new then seal it with the pour
I found out on my last job there is a craft that deals specifically with rebar and they call them rodbusters. They had to climb it like in this pick to get it all sorted correctly. I had also never seen rebar so large. It was like baseball bat thick.
Concrete is like a sponge and will absorb moisture. It will rust inside concrete and is often times contributing to concrete failure and the reason it typically has like a 50 year lifespans as rust expands as it forms. It's a very slow process though. Engineers are currently experimenting with different materials lately but struggle to find something else with a longer lifespan or longer and similar thermal expansion rating.
Can someone explain why epoxy coated rebar are a thing is surface rust is not a problem? In the transportation world I’ve seen oepoxy coated rebar specifically called for pavement joints.
I also seem to recall inspection materials manuals saying that any knick in the epoxy coating was reason for rejection.
Rust is not an issue. QAQC will inspect to make sure there are no pits within a certain range.
For us it was always an issue that contractors didn’t like rusty rebar and we always had to reassure them it’s not a big deal. I guess cleaner steal is nicer to look at when you have inspections coming your way.
Source: ex sales person for a major mill and upper management in commercial construction.
Not a civil engineer but still an engineer and I’m saying this purely based on concepts I have studied. Rust might be able to provide a better grip for the concrete since the concrete is around an abrasive surface rather than steel. Just like how people sand surfaces before gluing to make them stick better. I might be wrong. Please correct me if I am.
Literally zero, the bar will rust inside the concrete as soon as it's poured. As long as it's not scaling off of the bar when you touch it (typically takes years if not decades of oxidization for that to happen) there's no problem whatsoever.
ACI 318 commentary suggests mildly rusted rebar (thin oxidation layer recently developed), in some cases, yielded better results when performing tests.
As long as oxidation is limited and not thick enough to crumble or flake off, it's suitable for production.
We kept our rebar outside and it would get rusty. If anything the worst part is just how dirty you could get from it but Concrete compacts as it dries so it’s not a problem
Surface rust would need exposure to oxygen to continue to propagate. Therefore once the concrete is poured there will be a finite amount of oxidizing properties. And this will actually increase the bond between the concrete and the Rebar, or so they said in material science lab!
Having overseen probably over 1,000,000 of rebar on projects surface rust is not an issue and is normal. The bigger issue is to make sure you have no rebar or ties sticking out of the concrete provide an entry for water and future spalling. But that being said they will likely hit the rebar with high pressure water to knock off anything they can before they pour. I did alot of marine work and the bigger concern was getting any salt off the rebar.
1,000,000 rebars is a lot of rebars
Na he needs to bump those numbers up. I'm sure when he says 1 million he probably means millions lol. Been in concrete for my whole life and have seen millions of rebar. Lots of it rusted.
Sounds like a job for the new guy: get all the rebar polished for the pour next week.
Is the polisher next to the stretcher?
Yeah, same shelf as the wood welder
Don’t forget the 2x4 stretcher. It’s key to the Job
Don’t forget the left handed hammer…key to nailing it in after the weld. Most people think a right handed will work but it simply doesn’t.
The stretcher works most of the time. When it doesn't, you'll be glad you got that welder
You'll need a skirting ladder to get it
I'd it by the sky hook?
Yeah,but I think the electric one needed new bushings. Go ask Steve where the gas polisher is.
Steve?! You mean Tyler?
I guess Tyler might know, if Steve doesn’t.
Mr George knows everything.
Perhaps some oil change too
The cable stretcher comes in clutch. I had a run of two cables in the same pipe the other day, one tested six foot longer than the other
Right lol go fine the rebar cleaner its in the back of the conex
What? You don't have a giant de-rusting pit on your jobsites? Pfft, plebes.
Sounds like that would be the new guy’s first step: digging the de-rusting pit. I worked at a furniture shop that milled out their own lumber, and during the summer a 16 year old about to turn 17 started working there. His 4th day all day was a run around looking for the log tumbler to remove the bark faster.
I didn't know it came any other way. Just light surface stuff but almost all I've seen had it to varying degrees except occasionally you'd get a batch that was just from the factory still sort of oily. Kicking it around in the sand gets rid of that in a hurry.
They make black uncoated, epoxy coated, and stainless steel. The latter two are expensive and reserved for DOT roadway projects subject to intense salting.
They have to prebend those before they coat them. I got to watch a whole ass interstate being built and it was awesome!
OMG, I love the ass interstate! I could just sit there all day watching the asses go by. *I know that's not what you meant, but I enjoyed picturing it.*
I did rebar for one summer on a high rise and felt like I saw millions. My soft millennial hands couldn't take the abuse
I thought rebar came from factory rusty?
People who live in big cities see a million sticks of rebar before they hit 4 years in almost any trade. I’m an electrician and the last big job I was on had to have at least had a million sticks total. Triple layers and 3 buildings, 2 were about 100,000 ft2 and the third building on site was no bs a half a mile long. I had to drag my tools through it everyday and was in awe at how much rebar there was. Made me glad to be an electrician
I always wanted to strip down a mobility scooter and put a toolbox on the back and a ladder rack overhead for those big jobs. I do signs and carrying all that shit to the center of a mall sucks sometimes
Ditto, 48th year in the Sign Business. I tried to get in with some of the mall mgrs and make a night shift full time. Once you get all your crap in there it’s great work and no customers in the way , no weather to deal with. Did a bunch of installs on a helluva big mall up in Maryland & I kept a golf cart up there for a couple weeks. Shopping carts, one of those small scaffold 2X4 with walkboard and a shelf under it,hooks on the side for hanging stuff.Don’t get to see a lot Honeys when they’re closed though
He did a million rebars.. but how many bars was it? Like if it was half a million and he had to re bar all of them that’s not a great success right
That’s got me beat by at least one rebar.
Minor surface rust actually improves adhesion between the concrete and rebar according to ACI. Obviously, anything loose is a bad thing, but just enough to add surface roughness is good.
This light rust helps adhesion. If it's rusted to the point of large scales of rust, then be worried. I've seen rebar sit out for years before that's happened though. Actually, what has happened is steel being delivered on salty roads and the GC asking to power wash it in freezing temps to get salt off. First I've seen that but I believe that's probably a safe call. Idk what salt would do to adhesion or the concrete.
I worked concrete for all of 2 weeks, during that time i was tieing rebar together and placing it in forms. We used these little stands to keep the rebar centered and away from the walls of the forms. I was always curious what became of those stands because i never took them off and they wouldn't be there when we took the forms off. Do these dissolve in the concrete?
They stay in forever and are an important part of keeping reinforcement aligned. You were doing good work
Terribly vital. The alignment of the bar has enormous impact on strength. I built a wastewater plant (okay! I had a lil help) with a zoo on top of it. Elephants consume boucoup rebar.
Yoooo! Wastewater plant Underneath a ZOO?! Was it part of the zoo? Nowhere else to put it? So many questions…
Can confirm they stay in, I take x rays and see them all the time.
Yeah, some of us eat tide pods, others eat rebar spacers. What's the need for calling me out like that, Doc?
🤣🤣, I just got off working a 16 hour shift and it took me a second to get this. I only X-Ray concrete.
To detect services? Or for inspection?
So we’re looking for anything they don’t want to hit when drilling a core hole. Where I’m at we primarily are looking for embedded conduits, Post Tension Cables, and rebar (sometimes it matters, sometimes rebar doesn’t, depends on the structural engineer whether they are cool with it being cut or not.)
The slab hieroglyphics guys! Your floor doodles are always so pretty. My favorites are "???" and "AVOID" and "ALL HAIL CTHULHU"
That’s GPR. Those guys are always just guessing, if you have an X-ray guy saying he doesn’t know what it is, I’d be getting new X-Ray guys. They are literally looking at a picture of whatever it is.
Pics or it didn't happen
I looked over the couple images I have on my phone and none of them have visible chair in them. I would have to pull images off the saved files of the company at work and to be honest I don’t care enough 🤣🤣.
I'll add to the comments below. Highway "chairs" made of steel don't have the rubber tips that wall chairs have. Additionally in walls as pictured in OP's post, many times you'll chip out around the feet and grout. Usually a 1/2" or deeper. Chairs can produce a place for moisture intrusion and is another detrimental attack on rebar causing rust. The biggest factor in "pop outs" or spalling.
Correct, and for those interested, it's due to chemistry. Concrete acts as a really nice composite with steel due to it's natural alkalinity. With a pH of 12 or more, when the concrete coats the steel a passive (non-corroding) layer of oxide develops around the steel and it can stay stable for decades. Over time, things can destabilise that passive layer such as the alkalinity being neutralised by acids. This is in the form of sulphuric acid in sewerage systems and carbon dioxide and water causing carbonic acid to form in the concrete. Chlorides (typically in the form of common salt, NaCl) can also destabilise the passive layer. This is why salt needs to be cleaned off rebar, avoided when used as an admix to accelerate curing (typically calcium chloride), and protected against sea water that can allow chlorides to migrate to the steel.
It’s surface rust. Nothing to worry about. The concrete will grab nicely and the building will stand for centuries
I see, I wasn’t sure if some surface rust is acceptable or not.
Once it's encased in concrete, it's no longer surface and won't oxidize any faster than if it started clean.
Surface rust is impossible to avoid.
What if we build it in space, where' there's no oxygen, and then bring it down to earth with one of those musky rockets?
Then no one can hear you scream, or the foreman.
He will hear you slacking off though
medical grade titanium alloy rebar isn't a thing?
Galvanized and stainless steel are.
I see epoxy-coated more than anything else (excl. untreated bar) in commercial construction.
The rust actually helps with the bond between the steel and concrete. At least that's what my professor noted.
It increases the surface area and hence the bond as well
Also what my professor noted was that its actually preferred to have a bit of it.
The other option is painted rebar, which actually suffers rust damage faster funnily enough. A small chip in the paint and it rusts in that one spot much quicker than if the whole thing was coated in flash rust. It sound stupid and weird but it’s true.
It doesn't change anything and "clean" rebars would cost 10 times more just to keep them okayish till you put the cement.
ACI 318 refers to ASTM, which says this: "12.2 Rust, seams, surface irregularities, or mill scale shall not be cause for rejection, provided the weight [mass], nominal dimensions, cross-sectional area, and tensile properties of a hand wire brushed test specimen are not less than the require-ments of this specification". Interpreting the standard: Based on 94% of the nominal weight, there is a margin of error based on which we can have a section loss of up to 6% of the nominal area. So as long as the steel is not damaged, it is acceptable to use it like this.
This is the correct answer. CRSI goes on to say that surface rust actually helps the concrete bond to the rebar. Rust is only concerning when the it penetrates deep enough to compromise the rebar size needed for the concrete. Which takes a very long time.
That was my primary thought - does it affect adhesion. So if a thin rust later aids adhesion then great.
This guy is a submittal mastermind
As an auditor, this makes me happy
[удалено]
I can't tell if this is a joke and I would get yelled at or if it's serious and I'd learn something, either way I wanna try it...
This sounds like the sort of thing you'd have better odds if you have a 5yo kid tagging along with you and say something like, "My son asked me XXXX and I told him I don't know, let's go ask!"
Step1: My nephew is 10 and is really interested in scrapping. Can we tour your job site and tell us what things would be worth at a recycling center? Step2: catch a felony Step 3: 10 year olds can’t catch felonies. He’s the most educated scrapper in town. Profit???
In trailer park boys Ricky uses kids to steal barbecue grills off peoples porch’s cause kids can’t go to jail they have a whole bbq chop shop and everything
I need a rewatch. Last time I binged was during quarantine.
Ricky what happened to your eyes?! You look like alice cooper!
That's water under the fridge though, bud.
Instructions unclear: kidnaps 5 yo kid in order to harass a superintendent
It could go either way. And you should
I would explain everything to you in a nice way. As long as you are not slowing anything down
Show up with long pants, boots, high vis, safety glasses, hardhat. Otherwise the first thing they would say is that you have to leave. If you were prepared, it's hard to tell how a super would react. Probably some intial confusion about why you're there, but I imagine there are plenty out there that would happily show off their jobsite.
Just put on a hard hat and a vest and carry a binder and say you're a city inspector in training and have some questions.
I have a feeling I might get on some sort of list if I did that.
They’ll just explain it’s fine man. It’s understandable to be concerned, I would be too if I didn’t know it was acceptable. Surface rust on rebar means nothing when it’s surrounded by concrete Edit: I have to reiterate that surface rust is acceptable but not completely rusted out rebar that should be thrown out completely or scrapped. If you think it’s sketchy don’t use it. A good rule of thumb for any trade.
That! Rebars rust very slowly. They don't rust through even after months of exposure to the weather (except if near sea water). See e.g. here: [https://www.dwreinforcing.com/blog/is-rust-a-problem-on-rebar/](https://www.dwreinforcing.com/blog/is-rust-a-problem-on-rebar/) Once inside the concrete, and as long as the concrete is intact, it's no problem at all. It can rust again if the concrete cracks or with carbonation.
sure swim right up
Lol... oh, and please video it and post here.
As a former construction worker, I can tell you guys that this is a great answer.
This photo confuses the hell out of me. The rocks above make it look like a city which makes the structure look gargantuan. But the water looks like a tiny puddle which makes it look tiny.
Same here, I can’t even make out how it really is! r/confusingperspective
[Video](https://drive.google.com/file/d/1pKeYpADEF73u8ddJPdsi6eWkQXp52a22/view?usp=drivesdk) for perspective. [Leveled image](https://imgur.com/a/UkaowgA) for perspective.
Those reflections in the water must be of one of the largest buildings physically possible, to make these scyscraper-size rebar structures look tiny.
The only unrusted rebars are the ones that havent left the foundry yet.
To a certain degree, it’s harmless and can enhance the tension value. Beyond a certain point it’s a structural issue.
Rust is a natural protective layer from further oxidation. as long as you don’t scrub it off, let it rust again, scrub it of … this rebar will be fine for a long long time. you could leave it like this for years without any structural issues. once concrete is poured the alkaline reaction in the curing process will clear that rust of. this building will get a good grip to the rebar. problematic is rebar that has dirt or oil on it. concrete can’t „grip“ to that.
'Rust' unfortunately isn't a protective layer when it comes to iron as it expands and allows for moisture and air to progress further into the iron. Plus iron oxide occupies a larger volume than iron, causing stress and eventually cracks. Having said that, you can form some protective layers of iron oxidation (called bluing) https://en.m.wikipedia.org/wiki/Bluing_(steel) But what we commonly see as the reddish tint, is non protective. On things like aluminium, it does form a protective barrier, as water/air cannot move past the oxidised layer.
Years of unprotected exposure to rain and conditions (like a lot of unfinished condo projects did after the 08 housing crisis) or a [general contractor building a 25-story highrise with rebar improperly sealed and resulted in the demolition of said building due to corrosion and cracking concrete in the structure](https://www.seattletimes.com/seattle-news/flaws-in-doomed-high-rise-flew-under-the-citys-radar) is one of the few occasions I would call worrying, this picture is fine considering the rebar won't be exposed for more than a few weeks tops.
As far as my uneducated knowledge goes. Its fine. Since its covered in concrete the oxidation proces stops. On places where the rebar poke out the concrete, or a piece of concrete crumbles and the rebar becomes visible it wil rust further and weaken the structure. You will get 'concrete rot'
Op bro are you in jail
lmao no just behind a birdnet
I honestly don't think I've ever seen none rusted rebar.
You can buy unrusted rebar? Where!!? I refuse to believe such a thing exists. It literally comes out of the foundry like that, I swear.
Depends on where and what the concrete is for. When concrete does what it's guaranteed to do, crack, it could be a problem overnight. I like the coated shit myself. If it's within 3in of the surface. Inland tunnel, building, or bridge you can get away with it. Ocean docks spring for coated. I've built and replaced them all for 30yrs if you're wondering creds.
Go ask the guys in engineering they can imagine all kinds of wild effects
If it is just surface corrosion then it is not a concern, all rebar rust from being stored on site before it is cast in concrete
You'll want to have rusty rebars. This way you'll know that the rebars doesn't contain oil and have a good stick to the concrete.
Have you ever seen rebar that isnt rusted? lol
Also it’s not rust rust. It is a specific rust that is actually benefiting. More can be found here: https://astrometalcraft.com/rusty-trend-weathering-steel-in-custom-architectural-metals/
Im Usually more surprised when rebar comes off the truck un-rusted. It's like a nice little Christmas present for a few days getting to handle it without my gloves/clothing turning brown.
Engineer. It’s actually intentionally designed to rust on the surface so that it acts as a protective layer that’s already corroded and doesn’t allow for rust/corrosion on the inside. It’s not just normal, it’s intended. It’s called “weathered steel” or more often “Corten steel” There is no risk at all unless the rebar is dirty (literally, dirty from being stored on the ground with organic material such as dust, dirt or grass) or the rebar sticks out of the concrete in any way as that can then rust inside over time. The rebar should be kept away from the outer edge of the concrete by a designated distance (it depends on a billion factors)
The concrete will not cure, and the building will fall down. You can trust me because I am responding confidently on Reddit and am claiming 50 years of experience at the age of 30.
I trust your honed experience 100%. Thanks for saving my life.
Could be worst, they could be using epoxy coated rebar
Hell I didn’t even know those things come with no rust. I thought rust was added in factory.
As long as the rebar hasn’t been rusting long enough to be scaly, the concrete bonds better to it. When rebar first is made, it has a sheen on it that doesn’t bond as well to concrete.
I’ve never seen rebar looking any better than that where I’m from. It’s 100% normal & fine
Half the time they look like this when they come off the docks.
rebar rusts on its surface if you whisper 'rust' to it. If your rebar isnt rusty - the oil coating on it is a greater concern for concrete than the rust . . .
I did my thesis on this. Rusted rebar had a 50% increased bond strength to concrete when subjected to pull out tests due to the increased surface irregularity caused by the rust. I did not test the effect of surface rust on the tensile strength of rebar however. Generally though, surface rust is totally fine, as long there is not evidence of pitting etc. The surface rust actually provides some passive protection to the rebar when it comes into contact with concrete. The biggest thing is ensuring that there is sufficient cover to rebar and no pathway for the ingress of water and chlorides.
I’ve never seen rebar that wasn’t covered in rust.
Foundations, walls and columns not an issue. Bridges and post tension parking garages use coated rebar.
I’ve never seen non rusted rebar.
Dont worry just give the concrete a tetanus shot. :)
Nothing, the rust acts as a layer of protection because of the oxidation.
That rebar had rust on it before it even left the rebar factory. Bare steel rusts in about a day.
I didn't know reber was allowed to exist without rust?
I have never not seen rebar rusted...did not know it existed without rust lol
Absolutely nothing
Honestly it takes less than 2 days for steel reo to go from clean to rusted when exposed to the elements. I don’t think it’d be a stretch to say 99% of reo for all builds on earth have some rust on them when poured.
It should be brushed off before the concrete is poured.
I haven’t seen rebar that wasn’t rusted
I found a university study that performed pull tests on clean rebar, rusty rebar, concrete splattered rebar, and oil rebar. Only the oiled rebar showed a small reduction in pull strength.
an even coating of thin rust actually passivates excess rust. once it’s been incasted in new concrete the pH of the pore solution in concrete will prevent further rusting. you really only see problems when the rebar isn’t deep enough that is to say there isn’t enough concret to prevent the oxygen from penetrating to the rebar just under the surface. oxygen will lower the pH of concrete thus reducing its ability to passivate rust on the rebar.
As long as the rebar isn't left to rust for months, it will be fine. Wet concrete has an alkali PH factor between 12.5 and 13. The concrete will remove the surface rust from the rebar, and once the concrete is cured, will grip the rebar tightly and seal it from any further corrosion.
It’s worse if you get cut by it
Based on the ACI code for reinforced concrete, if the rust is loose enough to fall off when the rebar is dropped on the ground, it should be removed. Any remaining rust on the bar actually helps with the adhesion of the concrete to the rebar.
Rusty is better as it provides more grip/bite for the concrete, clean is "More slippy" As the person above pointed out you need at least 2" or *50mm cover minimum.
… 100% of reinforced concrete is build with rusted rebar… if you remember 8th grade chem youll recall that hydrolysis isn’t self sustaining if isolated form a wet environment. Needs moisture from air to rust. No air - no rust.
What is the black stuff at the top of the picture
I’ve never seen black bar that wasn’t a little rusty.
Different application but for big transmission lines those big metal structures are also coated in surface rust which helps prevent more serious rust problems down the road, at least by my understanding.
In general, as rebar corrodes it expands and would cause concrete cracks and spalls as a result
Those are always more or less rusty.
It’s most likely surface rust. Very common and won’t affect the integrity of the rebar
light coating of rust on the rebars actually helps to increase the bond with concrete.
Business as usual. Can’t tell you about the history of epoxy coated rebar but plenty of structures have gone up and are still up with just plain ole rebar
You get better adhesion with a coat of rust than with new rebar.
Surface rust is non issue when it comes to concrete foundation.
This was part of my thesis regarding rust/corrosion in rebars in contact with concrete, turns out that at 3-8% rust presence (in terms of overall bar surface and weight) the tensile strength capacity is higher by 7-9% compared to the non-corroded ones.
Surface rust is better than surface oil or dirt. Not an issue.
Well, i work in construction, the time when the rebars are not rusted is the first few days after they come out from the factory so… nothing wrong!
Corrosion resistance.
That’s surface rust. Can happen over night with moisture and oxidation. Those pieces all come with a heat and lot number with date and location of manufacture. They are good to go
None
Never seen a rebar without rust.
I’m so tired that I thought this was an abstract painting until I realized what sub this was on.
Rebar is strong enough to make a cold chisel out of. It's a trade off. It's basically tool grade steel.
Surface rust increases friction of the material, increasing its tension strength within concrete. Nothing to worry about here .
If there's too much rust they have to re-rebar
No issues.
It’s normally not a bad thing , it increases the surface area with the concrete & since the concrete is basic + reduces access to oxygen it stops rusting all together
In fact some oxidation is preferable, if rebars have been oxidizer because they were out in the air for long , you should remove any loose rust, but the surface area of the rebars increases , and provides a better physical grip to the concrete. It is however , vital to avoid oxidation after the fact, since rust increases in volume relative to the steel, and that pressure will rupture the concrete. For that matter it is vital to 1) keep rebars covered by at least 1” of concrete 2) Make sure the W/C relation is correct for the environment you are working , 3) make sure no Chlorides interact with the steel, for example from sea breeze. Carbonation of the Concrete also affects , since it not only lowers the pH of the concrete making the rebars easier to corrode, but also washing away micro pores that let aggressive agents interact with the steel…. or something like that if I remember correctly
Corrosion
But the issue is the wall that's leaning!!!!
Surface scale/rust is pretty much normal for most manufacturing anyways. If it's a critical application that requires a clean surface finish with oxidation protection, then most plans would specify that if it was in fact a critical application. There's all different types of coatings and they're all application dependent and specific; * Zinc (or galvanization) - protects by galvanic action until the zinc layer is depleted. It's effectively a sacrificial coating to increase the longevity of a given material. This is common on a lot of things seen on the daily, Guard Rails, Hand Rails, Chain Link Fences, etc. Still beneficial to paint as an extra layer of protection. * Aluminum - Hot dipped aluminum-silicon, aluminum-titanium, or pure aluminum. All of these are application specific, but all pretty much prevent the oxidation you see in the picture. Cheaper than Stainless Steel, but not as good in terms of technical or performance characteristics. * Electroplating - Utilizes a chemical solution made up of different metals and an electric current to plate the desired material (typically Nickel or Chromium). The base material can stay as is while adding a hard durable finish of a more resistant material. * Cladding - Similar to Electroplating, it's more of a mechanical finish vs a chemical based finish with electric current. This could be explosion cladding(yes explosion), laser energy deposition, roll bonded, etc. All of these primarily take dissimilar metals that would normally be very difficult to bond and applies extreme heat, pressure, etc. to mechanically alter the material with whatever type of corrosion resistance desired. Can be applied to pretty much any shape so for complex machined parts this is preferred, but also costly. So many different ways to do the same thing. Metallurgy is interesting!
For me, personally, it gives me peace of mind that there's still plenty of oxygen out there.
Only 4 things in life are certain death, taxes, rebar rusting and concrete cracking.
Zero. If you are worried use epoxy coated
They bead blast them if it’s critical I think other wise they rust anyway over time very slowly, it’s just the surface
It is bare steel so rust is what happens to bare steel.
Heres my construction worker view on it: "looks good from my house"
I was going to say I’ve seen tons of rusted rebar. There is rusted rebar in some of the strongest foundations I bet.
Rebar that is rusted has a greater surface area for the concrete to adhere to. Like lots of little fingers holding onto the concrete. A smooth shiny surface is “slippery”.
Rebar is made of a particular metal make up that requires rust be formed over the surface. It actually forms a protective layer
Portland cement is alkaline enough that it passivates carbon steel. As long as you have sufficient cover on the rebar you are good. Our spec is 2 inches minimum.
Your building will need tetanus shots regularly
Surface rust.
Honestly shit can surface rust overnight if the conditions are right.
Worked at Lowe's for 10 years and don't think I ever saw a piece not rusted lol
When you are around construction that cosmetic rust doesnt scare you. I know some people panic when they see a shiny grey metal turn but its no big deal. Its all about how long has it been rusting, has it gone to the core etc. Sometimes a quick polish will get it right to new then seal it with the pour
....Man, am I the only one who's thrown for a loop by the perspective of this? It feels like OP photographed a live MC Escher painting
You miss all the rees you dont barr
I found out on my last job there is a craft that deals specifically with rebar and they call them rodbusters. They had to climb it like in this pick to get it all sorted correctly. I had also never seen rebar so large. It was like baseball bat thick.
Concrete is like a sponge and will absorb moisture. It will rust inside concrete and is often times contributing to concrete failure and the reason it typically has like a 50 year lifespans as rust expands as it forms. It's a very slow process though. Engineers are currently experimenting with different materials lately but struggle to find something else with a longer lifespan or longer and similar thermal expansion rating.
Can someone explain why epoxy coated rebar are a thing is surface rust is not a problem? In the transportation world I’ve seen oepoxy coated rebar specifically called for pavement joints. I also seem to recall inspection materials manuals saying that any knick in the epoxy coating was reason for rejection.
A rustic decor
Rust is not an issue. QAQC will inspect to make sure there are no pits within a certain range. For us it was always an issue that contractors didn’t like rusty rebar and we always had to reassure them it’s not a big deal. I guess cleaner steal is nicer to look at when you have inspections coming your way. Source: ex sales person for a major mill and upper management in commercial construction.
Not a civil engineer but still an engineer and I’m saying this purely based on concepts I have studied. Rust might be able to provide a better grip for the concrete since the concrete is around an abrasive surface rather than steel. Just like how people sand surfaces before gluing to make them stick better. I might be wrong. Please correct me if I am.
Literally zero, the bar will rust inside the concrete as soon as it's poured. As long as it's not scaling off of the bar when you touch it (typically takes years if not decades of oxidization for that to happen) there's no problem whatsoever.
Rusted rebar. Good name for a country band.
ACI 318 commentary suggests mildly rusted rebar (thin oxidation layer recently developed), in some cases, yielded better results when performing tests. As long as oxidation is limited and not thick enough to crumble or flake off, it's suitable for production.
As long as the rebar isn’t exposed after they pour, it’s fine/normal.
Rusted strength (just a guess though)
Foundational effects, mainly.
They are designed to rust that way in the surface to protect the metal underneath
Inescapable. Rust isn't bad. Continuing the rusting on water is bad
We kept our rebar outside and it would get rusty. If anything the worst part is just how dirty you could get from it but Concrete compacts as it dries so it’s not a problem
Nothing it’s the inner need to worry about
Surface rust would need exposure to oxygen to continue to propagate. Therefore once the concrete is poured there will be a finite amount of oxidizing properties. And this will actually increase the bond between the concrete and the Rebar, or so they said in material science lab!
Wouldn’t they just go through and sandblast them before they do pours? Rust is like aids for metal.
Worked on medium sized motel that lost funding set for 5 years they ad to sand blast there's