Cutting methodology of rebars

[rameshchandrapatel]

On one of my project's structural member, the Site Engineer In charge cut the rebar with gas torch cutter.

The Quality manager immediately ordered the work to be stopped and issued NCR.

What is the reason that rebars need to be cut with a rebar cutting machine and not gas torch cutter ?

Need your valuable answers. @HockeyPuck @Dnyan Deshmukh @Srinivasan

 

[HockeyPuck]

Give your QC Manager a pat on the back - I'd say he made the right call. A good call.

Torch cutting heats the steel and changes the metallurgy of the steel's properties, plain and simple. I'm going to guess that the Contractor didn't have a steel cutting chop saw with him and opted to flame cut them because he had bottles on his truck. Really, the time to cut them with either method is relatively the same, it's just a matter of having the right tools for the job....

I'm sure the Contractor would argue that the degradation is at the ends of the bars and not necessarily in a structurally-influenced zone, but, rebar works in shear and tension to some degree no matter where it is in the structural element, middle or the ends - The goal is to not have degraded material in our structures.

I'm curious: Do your job specifications address flame cutting? And what was the Contractor's response when the QC Manager shut him down?

 

[rameshchandrapatel]

Give your QC Manager a pat on the back - I'd say he made the right call. A good call.

Torch cutting heats the steel and changes the metallurgy of the steel's properties, plain and simple. I'm going to guess that the Contractor didn't have a steel cutting chop saw with him and opted to flame cut them because he had bottles on his truck. Really, the time to cut them with either method is relatively the same, it's just a matter of having the right tools for the job....

I'm sure the Contractor would argue that the degradation is at the ends of the bars and not necessarily in a structurally-influenced zone, but, rebar works in shear and tension to some degree no matter where it is in the structural element, middle or the ends - The goal is to not have degraded material in our structures.

I'm curious: Do your job specifications address flame cutting? And what was the Contractor's response when the QC Manager shut him down?

@HockeyPuck Thanks for replying.

The QC Manager ordered the rebar to be replaced.

The contractor had to adhere to the decision as QC Department had issued NCR.

Without closing of NCR, reimbursement of Running Account Bills is not possible as per client's policy.

 

[Dnyan Deshmukh]

Steel mostly used for construction is HYSD bars it have hard surface outside and mild core inside. I am not familiar with production process of steel, soon going to plan for visiting steel manufacturing plant.

The process of steel manufacturing like melting, moulding / casting is done at certain temperatures. Steel is good conductur of heat and its molecule pass on the heat from one end of bar to the other.

If we melt the steel during flame cut, it transfer lot of heat to another end and when that bars get cooled down, the whole internal structure of steel and its roperties gets changed, i can not say about, how deep it make impact but steel made once gets melted and reformed, it definately loose its properties and become something else with unknown properties.

To ensuer no uncertainties in construction, heating of steel bars by flame, by welding arcs or by any other mean is not permitted.

There is nothing more that i can technically explain until i visit steel plant and have talk with technical expert of that field.

Will definately write the article on how steel is manufactured and how it may get spoil if we do those non permitted activities with it.

To ensure safety of structure we should nit allow the heating of installed reinforcement steel bars.

For cutting of steel bar we can use hand grinder cutter, it take lot of time but does job well.

May i know the reason, why the cutting of steel bars is required in that work, is it was the last slab of structure.

 

[rameshchandrapatel]

Steel mostly used for construction is HYSD bars it have hard surface outside and mild core inside. I am not familiar with production process of steel, soon going to plan for visiting steel manufacturing plant.

The process of steel manufacturing like melting, moulding / casting is done at certain temperatures. Steel is good conductur of heat and its molecule pass on the heat from one end of bar to the other.

If we melt the steel during flame cut, it transfer lot of heat to another end and when that bars get cooled down, the whole internal structure of steel and its roperties gets changed, i can not say about, how deep it make impact but steel made once gets melted and reformed, it definately loose its properties and become something else with unknown properties.

To ensuer no uncertainties in construction, heating of steel bars by flame, by welding arcs or by any other mean is not permitted.

There is nothing more that i can technically explain until i visit steel plant and have talk with technical expert of that field.

Will definately write the article on how steel is manufactured and how it may get spoil if we do those non permitted activities with it.

To ensure safety of structure we should nit allow the heating of installed reinforcement steel bars.

For cutting of steel bar we can use hand grinder cutter, it take lot of time but does job well.

May i know the reason, why the cutting of steel bars is required in that work, is it was the last slab of structure.

Not the last part, but no front was available for further execution of casting work. So stopper was installed. Only 1 metre lap length was allowed and remaining protuding rebar was cut.

 

[HockeyPuck]

@HockeyPuck Thanks for replying.

The QC Manager ordered the rebar to be replaced.

The contractor had to adhere to the decision as QC Department had issued NCR.

Without closing of NCR, reimbursement of Running Account Bills is not possible as per client's policy.

Hopefully the Contractor was able to make the appropriate corrections without too much of an issue. It is unfortunate when work has to be removed & reinstalled, but hopefully the incident serves as a Lesson Learned for everyone on the project team moving forward....