What is the difference between TMT and twisted rebars?

TMT and twisted rebars

What is the difference between TMT and twisted rebars?

TMT and twisted rebars are different in the way they are made, although both are high strength reinforcing bars. Twisted rebars are basically done with older technology process of cold twisting, whereas TMT bars use modern day hot twisting technology. Here are few specifics that may help you understand the process better.

TMT and Twisted rebars

TMT Bars: Treating TMT bars have 3 stages – quenching, self tempering and atmospheric cooling. During this process, the steel bars receive a short, intensive cooling as they pass through the specially resigned Tempcore Water Cooling System after the last Rolling Mill Stand. The sudden quenching converts the surface layer of the steel bar to a hardened structure. Also since there is no twisting during this process, torsional stress do not create any surface defects, making TMT bars more corrosion resistant.

TMT Rebars are integral to every construction project. During construction TMT rebars and concrete complement each other in a way that Reinforced Cement Concrete (RCC) structure can be moulded into any desired shape, with the rebars providing the requisite tensile strength to withstand the load.

CTD (Cold twisted deformed) Bars: During the making, the bars are kept in natural cooling and being twisted at room temperature. Due to this process, the grains inside the bar turns into crystal, that provides the required strength. These kind of bars also have few disadvantages. The twisting process has adverse effect on the steel ductility. Also it breaks the protective blue oxide leaving the CTD bar open to corrosion.CTD rods are called as Cold Twisted Deformed.

The method of twisting the rods generaly increases the tensile strength of rods. After steel rods gets cooled twisting is done. Here at this time the topmost and near topmost fibres are getting ruptured while it is twisted, which ends in the formation of micro cracks over the surface of the finished steel rods. If these cracks are carefully seen in microscope the width of cracks is more at the topmost fibre and gradually reduces when it goes deeper into the section. These cracks gets water or water molecules which are harmful to steel or it may be the major cause for RUST. Hence the use of CTD rods are not advisable.

These are the difference between TMT and twisted rebars. For more details, please visit Rebar People to avail our services and clarify your rebar related queries. You can contact us by phone and email.