TOR Steel / CTD Bars
The TOR steel is also called as Cold Twisted Deformed (CTD) Steel Reinforcement Bar. TOR Steel bars are bars made with surface deformations formed by twisting the steel after elongation. The elongation process increases 'yield strength' from 250 to say 500 MPa. The surface corrugations impart higher bondage with concrete. TOR steel is one of the best grade of steel used in concrete reinforcement.
Note: TOR is a Brand Name originally marketed by TORISTEG STEEL CORPORATION of Luxembourg, Germany.
TMT Bars
TMT (Thermo Mechanically Treated) steel bars are relatively newer variety of steel used in construction. Due to their Thermo-mechanical treatment, TMT Bars are highly rust and corrosion resistant, hence they are best suited in humid and coastal areas for construction.
TMT bars are also known as 'Quenched and Tempered re-bars', because of the quenching and tempering processes involved in making the bars. The quality of TMT bar depends on three major factors:
A] Quality of raw materials used,
B] An automated mill which is properly designed, and
C] A well-designed quenching and tempering process.
The softer core with a concentrated hardened periphery, coupled with high elongation as required in seismic zones TMT Bars can have the desired tensile strengths. Depending on the size and grade, rebars with hardened periphery of about 15 to 30 per cent of the cross sectional area of the bar are ideal for civil constructions.
TMT bars are also known as 'Quenched and Tempered re-bars', because of the quenching and tempering processes involved in making the bars. The quality of TMT bar depends on three major factors:
A] Quality of raw materials used,
B] An automated mill which is properly designed, and
C] A well-designed quenching and tempering process.
The softer core with a concentrated hardened periphery, coupled with high elongation as required in seismic zones TMT Bars can have the desired tensile strengths. Depending on the size and grade, rebars with hardened periphery of about 15 to 30 per cent of the cross sectional area of the bar are ideal for civil constructions.
TMT Bars vs TOR Steel
TMT Bars give many advantages over other types of steel since 'Twisting operation' is not involved in their production. They offer better corrosion resistance since there are no residual stresses involved in therm.
Advantages of TMT Bars over TOR Steel:
- TMT Bars offer better safety for structures since they have higher Strength and Ductility.
- TMT Bars have greater ease of use due to better Ductility and Bend-ability. Pre-welded meshes can be made away from construction site. Avoiding manual binding at construction site reduces construction and fabrication cost and time.
- Since TMT bars offer high thermal stability, they can be used in building structures with very high temperatures like Chimneys, Foundries etc.
- The 'Cold twisting process' in formation of CTD bars causes surface stresses. On other hand, the TMT process gives TMT Bars superior strength and anti-corrosive properties. Hence TMT bars are better in resisting corrosion.
- TMT bars have better work-ability and bend-ability since they have very high elongation values and consistent properties through out their length.
- TMT bars offer better earthquake resistance than TOR Steel bars. TMT bars have high fatigue resistance to Dynamic and Seismic loads due to their soft ferrite-pearlite core. This makes them most suitable for use in earthquake prone areas.
- TMT bars are more malleable than TOR Steel bars because of their flexible nature.
- TMT bars have low carbon content in their composition, they can be used for welding joints without reduction in strength at the weld joints. Hence they are preferred for their fine welding features.
- The external ribs running across the length of the TMT bars give them superior bonding strength between the bar and the concrete. They fulfill bond requirements as per IS: 456/78 and IS: 1786/85. Hence TMT bars offer better bonding strength
- TMT bars are highly cost-effective as compared to TOR Steel bars. A combination of high tensile strength and better elongation value gives users better savings and reduced shipping and transportation costs.
