Can we use recycled steel bars from 2 years old concrete in columns 1

[precast123]

Hi,

Can we use recycled steel bars came from a concrete block casted 2 years back. The steel is in the form of square rings which will be straighten up and used in the columns. Please suggest.

 

[TehMightyEngineer]

Short answer is maybe, but probably not.

If they were already straight then if you cleaned them up they probably would be fine. But since you're rebending them I highly doubt they're going to be acceptable (typically you're only allowed to bend rebar once, in one direction) or straight enough for that application.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[ACtrafficengr]

After straightening, the residual bending stresses would still be there, compromising the steel's strength. A professional heat treater might be able to anneal them and relieve the residual stresses, but then you'd need a QA/QC program to make sure it worked. Even then, it might not be permissible. It would be much easier and cheaper to buy new.

 

[Ron]

Agree with above. The bars have been bent once already. Straightening them out will increase the strain hardening and can introduce cracking, depending on the quality of the rebar. Don't re-use.

 

[precast123]

So, if its not to be bend again it can be used? The rebar dia is 16mm. It is recovered from a concrete block 2 years old (2.5x2.5x0.5m)which was never put use. Will it not lose any strength when compared to new rebar?

 

[TehMightyEngineer]

If cleaned of concrete (well bonded mortar can probably be left on the bar), has not lost any cross-section (not likely if only 2 years old), undamaged during the removal, and wasn't overloaded during it's previous use, and of the correct grade and size; then you could reuse it in my mind.

99% of the time it's going to be cheaper to just buy new bars, though.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com