huangyhg

#9 bar broke while bending
i had a #9 bar bend at 90 degree. there were total 56. 4 of them were broken while a labour tried to move them for adjustment.any thoughts on that, how concerned u r with the quality of steel or wrokmanship.
i would be very concerned about the quality of the steel. take one of the broken sections to a testing laboratory to run tension and elongation on the bar. in addition, have chemistry done on the specimen and then compare that to the mill certificates if you can get them, or at least to the specification it was supposed to meet (such as astm).
rebar shouldn't be that brittle.
you might want to get a metallurgist if the local lab doesn't do that. would be good to check the grain characteristics and inclusions near the point of failure.
rebar is usually made from recycled scrap steel and has the potential to have non-metallic and non-ferrous metal inclusions in it. after all, they toss entire smashed cars (some of them get chopped into smaller pieces before being incinerated) into the furnace and the crud floats to the top of the molten steel as slag.
what was the radius of the bend? how much were the adjustments? i have seen some contractors want to do some crazy things using pipes to get leverage to bend rebar multiple times.
check bend geometry for one thing. check out what "moving them for adjustment" means, as well. it doesn't sound like he was just moving them over by hand. check mtr's on the material.
ron- your comments on source of rebar are correct, but keep in mind this is the source of a lot of steel (ie, structural steel, plate), not just rebar. this is seldom a problem in plate work.
rebar has specific properties required (aashto m31 or astm a615). in my opinion, while the specifications do not make it mandatory, you must insist on actual mill certificates when ordering and taking delivery of the deformed steel rebar. to have the bars 'break' after "hopefully" just a little adjustment is not normal and ron has very appropriately indicated that you should be worried about the quality of the steel. astm a36 governs plates.
was this a "field bend"? if so, did they use a torch to heat up the rebar before bending? this could cause the bend area to become very brittle after cooling.
1) the original bend could have been made with too small a pin size causing too small a radius of bend and the bars are damaged at the bend.
or
2) the bars could have been improperly "adjusted" in the field using a pipe or flame or both and the bars are now damaged at the bend.

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