Have you ever got a batch of brittle rebar?
I got 20 sticks of #5 today (grade 60) . Heard a snap and thought my helper was cutting the stuff in the rebarr bender. He had this weird look on his face and said the bar he was bending just snapped in two. We both agreed it was odd and went on with our work. A few hours later I was bending a piece and it snapped on me.
What is going on here? Same vendor, same bender, same everything except new batch of rebarr. Have you ever had this happen to you.
Lumber yard to pick up the remaining rebarr and I will get new stuff elsewhere.
We got a little scared after the second bad piece. Not too good for the concrete strength maybe and sure is dangerous for the person bending it.
I should add that we did do maybe 3-6 bends from this batch of rebarr with no problems.
Replies
never heard of that...
time to get on the horn and look into it....
slag spots or it had been tempered...
what radius are you bending...
proud member of the FOR/FOS club...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Edited 1/21/2005 11:04 pm ET by IMERC
if you was close I could test a piece for you and tell you how many pounds of pressure it take. if you are uncomfortable with it, get a local soils lab too test it.
slag spots or it had been temoered...
Not sure what you mean by slag spots, no slag or anything else for that matter was seen. I assume "temoered" is a typo for tempering, who knows knows what went wrong. It was just supposed to be plain jane regular rebarr.
As far as the radius , I'm not sure, 4-6" is my guess. It's a regular old rebarr bender.
I'm stumped
slag would be a section of the par that is mre like pot metal...
and that was a typo... a hard brittle spot..
time to get something done or the liability may catch up with you latter...
proud member of the FOR/FOS club...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
I'd hang on to the manufacturer's tag / batch number. The mill would probably be interested in testing the bar that failed, given the liability should a structure with their mill mark on it suddenly collapse from tension failure in the future. Your local building inspector might appreciate a heads-up, if he's smart.
Maybe it is not rebar they sold you, is there salt on them do they taste good with cheese dip, could be pretzel.
I've had a brittle batch before...you're bending along like usual and then you get the bender handle down with all your weight on it and SNAP! Think fast or smash your knuckles. To be honest, I don't think my boss did anything about it. Don't you just love 60 grade?
Perhaps a bad batch or spots in the steel but it also occurs to me it might also, at least in part, be related to temperature. I know that steel can become brittle.
Some alloys much more than others. One explanation of why the Titanic went down so fast was that the steel had a high sulphur content, not uncommon in that day, that made it quite brittle at low temperature. A standard trick for thieves faced with steering wheel locks was to use a can of freon to 'freeze' the steel and then shatter the bar with a sharp blow from a hammer.
Seeing as that some portions of the country are quite cold, I understand something like -20F in some areas, it would seem some might experience such problems. Especially considering that rebar is a fairly low purity steel originating as various and low grade scrap.
Being in Florida I seldom have such problems, inclusions and slag can be be troublesome, but come Sunday it may be down to the low twenties here.
Yeah, I had the same thoughts.Some Liberty ships in WWII sunk when launched because they had such poor steel that 40F water was below their ductile-brittle point. That's extreme, but demonstrates how bad the problem can be.Yes, I had -20F this last week, don't know what the poster had locally. Even 30 or 40F could cause a problem that would never arise at 60 or 70F. Note that it is "ductile-brittle POINT" The transition is abrupt and specific to that batch of steel. 5 degrees warmer and you might never have seen the problem.If you are building a bridge on I-95 in CT, then there are lots of issues and you are right to be worried. If you are working on a cold day, but the concrete is for a conditioned space, it is less of an issue.David Thomas Overlooking Cook Inlet in Kenai, Alaska
A standard trick for thieves faced with steering wheel locks was to use a can of freon to 'freeze' the steel and then shatter the bar with a sharp blow from a hammer."
....or go for the weakest link. Bolt cutter to the steering wheel.
WSJ
I've had it happen with galvanized rebar but not regular stuff.I'd do same as you ,send it back .
mike
If it is graded it must meet certain specifications. What happened to you is something to discuss with the steel supplier. It may be that the stronger steel is more brittle, and should not be bent, or bent below a certain radius or below a certain temperature. The steel supplier will have all that information.
A phone call to a civil engineer may be instructive as well.
What are you bending with? I got a long lecture from my structural engineer on this. All the standard manual benders on the market have a bend radius that is too tight for #5 grade 60 -- and Grade 40 on many brands. Even if you bend it without breaking, you have weakened it.
I use an electro-hydraulic bender made by Ez-bend that is rated for #6 Grade 60: http://www.ezebendinc.com/
I don't remember the bend radius, but it is a lot larger than the manual benders rated for #5 Grade 40. Once I determined that the radius was large enough to satisfy the structural engineer I forgot the numbers and moved on.
I can't believe what a time saver this unit is. The big advantage is you can bring the cutter and bending heads to the work. No measuring or marking and hauling bar to the bender, just put the bar in place and bend or cut to fit. Another advantage is you can make bends that are not practical with manual benders. 3D pretzels are no problem.
I recently loaned this bender to a friend who had the same problem as you. It worked fine.
A lot of import steel doesn't have the right technology for good steel, or even rebar quality steel. The way I get it, to make steel you have liquid cast iron that you add air/oxygen to (the Bessemer process) which changes the carbon content of the iron to steel. It sounds like the rebar is brittle like grey iron.
My steel supplier in Baltimore (Metals Express) had a similar story about an abandoned cargo of rebar they bought from the docks at a deal. When they put in on their shear to cut into the lengths they deal with, it would snap near and far into pieces.
All this rebar talk reminds me of a crane operator story.
Somehow or another, we got hold of a new boom truck operator in our area...since he had no miminum fee, he was a good fit for us so we gave him a try. The guys shows up with an old rig, completely revamped...new motor, all painted and all new straps and riggings.
One of the truss setting tools that he shows me is some "S" shaped "truss hooks". He had made these out of rebar...heating with a blowtorch and sharply bending the shapes. As soon as I spotted those I knew they would be trouble...so I asked him...."what are you going to do with those?" He said "they can hold two trusses...I made them myself". He was very proud. I mentioned that they must be brand spanking new and he hadn't ever actually used them on anything and he nodded yes and wondered how I knew. "Because they would break if you actually hooked anything with them"! AS I said that, I snapped them in two with my bare hands.
You should have seen the look on his face.
blueJust because you can, doesn't mean you should!
Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!
reminds me of the radioactive rebar story, but I've seen a fair amount of substandard rebar lately , visiting as many jobsites as I do I'll bet I've seen several pieces snaped in two during an average week and knowing construction as well as I do I'll bet there are many more pieces in the concrete just tie wrapped together!
Radioactive ?
The person you offend today, may have been your best friend tomorrow
Yeh it seems a while back the sold the metal from a reactor plant and it was melted into rebar. They got caught hauling it thru a military base to use for contruction , sent back and sold elsewhere..
Don't remember the full details.
Yeesh.My luck, I have some of it sitting around here.;)
The person you offend today, may have been your best friend tomorrow
Tim: Back about 7 yrs ago, when I was doing the foundation for my house, I got a bunch of rebar from Home Depot. Criteria was for 20K Rebar. Now 20K rebar should be pretty ductile, but this stuff was brittle as glass. Also, a real B-itch to cut - and bend! Obviously harder than it should be. Further you bent it, the harder it got. That made sense, as you were work hardening it as you exceeded its break point in the stress-strain curve. But then it snapped. Found out it was really 60K bar! That's when I learned how to read the crappy forged in markings on the stuff. Went to a real, registered, practicing professional civil engineer I know & talked to him about it. His answer is roughly as follows: You are hard-pressed to find any 20K Rebar any longer - most of it is 60K. And - most of it is pretty brittle. Said there was no standard for ductility on it - just tensile strength. That's why it can be so cheap. Went on to say that the stress that causes failure comes in bending under load - as you discovered. That to reach that point in a poured concrete piece was nearly impossible, since you can't bend the concrete that far. So...brittleness doesn't matter as long as you don't excede the tensile strength, where it will fail anyway. Remember that a designer cranks in a significant safety factor in calculating allowable loads just to cover this sort of problem. Make sense? Different colored horse (See the Wizard of Oz for photo) for structural members not embedded in concrete. Then ductility becomes critical.
Don
So what are you supposed to do, anneal it at the bends? Is it possible to warm it enough to bend without affecting the tensile strength?