Steel has been an integral part for all types of constructions for decades now. Its uniqueness lies in the fact that it reinforces the concrete which protects the construction structure from easy wear and tear that can occur from rust or any natural calamity like an earthquake.
There are different types of steel bars that are of different categories. Generally, the property and type of steel bars varies depending upon the geographical and environmental factors. Till the 1990s, TOR steel was used vastly. Later on, TMT bars superior ductility and other qualities gradually captured the market.
TOR STEEL AND TMT BAR
TOR is the brand name for ‘Toristeg Steel Corporation’ of Luxembourg. The word ‘TOR’ came from a French man by the name of TOR who brought 1000 lbs of steel over a boat. Then later it became synonymous with Cold Twisted Deformed (CTD) steel bars. For a period of time from the seventies to the nineties, TOR steel, as a high adherence steel was one of the best grades of steel used in concrete reinforcements. Produced from mild steel billets with limited carbon content, TOR steel had more tensile stress than anything else then. Its high elasticity value came from the surface deformation created by twisting of the steel after elongation. Subsequently, this created residual stress which made TOR steel corrosion-prone.
TMT (stands for Thermo Mechanically Treated) Bar, also called as Reinforcing Bar or Rebar in CIVIL ENGINEERING terminology, is described as a high-strength reinforcement bar with a tough outer core and soft inner core. Since its introduction, TMT bars have time and again proven itself to be extremely viable for reinforcing concrete structures. Today, TMT bars are commonly used as tensioning device to reinforce concrete, helping it resist compressive forces.
Known for its high-strength, sturdy built and robust appearance with the capability to provide better reinforcement to any concrete structure, TMT (Thermo Mechanically Treated) Steel Bars are ideal for building earthquake-resistant structures. They not only help to minimize the effects of damages during any seismic activities but they also offer the perfect optimum balance between toughness and flexibility (Elongation). Further, they also possess high yield strength and greater tensile strength, flexibility, and ductility than mild steel.
DIFFERENCES BETWEEN TMT BAR & TOR STEEL
The processes through which both TMT bars and TOR steel are manufactured are different, giving them unique properties. However, the TMT bars have clear advantage over TOR steel, possessing superior unique properties. This is the reason as to why TOR steel is less preferred.
- TENSILE STRENGTH: TMT bars have higher value of yield-strength when compared to TOR steel. For an applied load on the structural element, usage of TMT bars will result in lower steel quantity whereas the use of TOR steel results in 20% more steel quantity. For instance, if the total steel consumption in a project using TMT bars is 200 tons, then likewise using TOR steel, it would be 240 tons. Thus, there would be huge saving in steel of 40 tons by using TMT bars.
- DUCTILITY: Ductility refers to the ability of any material or structural element to deform, without collapse even after reaching the failure load. TMT bars possess superior ductility when compared to TOR steel, allowing them to protect construction structures from rupture and structural collapse. Further, TMT bars also possess extraordinary strength which allows them to help a building structure acquire 20% extra strength. More importantly, all of it built with the same amount of steel as used in conventional steel bars.
- ELONGATION: Elongation refers to the ability of any material to elongate before failure. It along with yield strain / deformation plays a major role in a steel bar’s ductility; the higher the elongation, the higher will be the ductility. Also, the higher the percentage of elongation, the lesser will be the chances of damage to the construction structure. When compared to TOR Steel, TMT bars with their hard outer layer and soft inner-core can elongate in a way that makes construction structures strong and flexible, well-insured from the dangers of natural calamities, like earthquake and so on.
- BENDABILITY: It is essential to give steel bars a desired shape, such as the end-connection of beam-column joints. Though both TMT bars and TOR steel possess a good track-record of bendability, TMT bars with their soft inner-core possess greater elasticity which allows them to bend more to achieve various shapes. Further, TMT bars (thanks to excellent elasticity) are equipped with better bending and re-bending properties. This makes them the easiest materials to work with that can be bent and molded into any shape during a construction project. Greater bendability of TMT bars helps construction structures to stay firm and strong even in adverse circumstances of natural calamities and other such dangers.
- WELDABILITY: TMT bars with low carbon content are highly weldable when compared to TOR steel. The low-carbon ingredient in TMT bars makes them a viable choice for hassle-free welding works. Furthermore, TMT bars require no pre or post-welding treatment, which makes them easier for construction purposes. Thus, construction designers and architects can create innovative structures without compromising in any way, the quality of the structures and strength of the TMT bars.
- DURABILITY: Resistance against the corrosion of steel bars is the key parameter in durability of the construction structure. This resistance depends upon steel bar’s chemical composition. The residual strain in TOR steel initiates faster corrosion process than in TMT bars that does not include twisting and stretching process. Thus, thanks to their manufacturing process and processing of raw materials, TMT bars stay highly resistant to corrosion. During any construction works, the TMT bars can stay exposed to water for a longer period without in any way getting affected. Traditional bars do not possess the anti-corrosive properties of TMT bars and hence remain vulnerable to rusting.
- SEISMIC-RESISTANT: Earthquake imposes repetitive loading for a number of cycles or cyclic loading in a construction structure. The process of failure under repetitive loading is called ‘fatigue’. TMT bars are intrinsically hard and strong than TOR steel. Initially hard and strong, TOR steel shows softening behavior later which makes them vulnerable to earthquake shocks. On the other hand, with their excellent concrete bond of soft ferrite-pearlite core and reinforcement strength, TMT bars can firm up the tensile strength of construction structures. This in turn allows them to absorb a greater amount of energy released during an earthquake, and also ensure the longevity of building structures.
- RUST RESISTANT: Failure in any reinforcement concrete happens due to corrosion. TOR steel corrodes in the concrete due to its high concentration of chloride ions. On the other hand, TMT bars due to their thermo-mechanical treatment are very highly rust and corrosion resistant which makes them ideally suitable for construction structures in humid and coastal areas.
- FIRE-RESISTANT: TOR steel contains low thermal stability. On the other hand, TMT bars with their higher thermal stability can retain more than 80% of the ambient temperature yield strength at 300Â°. This helps the construction structures to stay safe and secure during fire disasters.
- FLEXIBILITY: When compared to TOR steel, TMT bars are extremely flexible which allows them to endure high temperature and humidity levels. In addition, they do not crack or break even after turning and bending 180 degrees.
- BONDING: TMT bars also bond better than TOR steel with cement. This is possible due to the superior bonding strength of the ribs on the surface of the TMT bars that run across the entire length. Combined with superior strength, TMT bars’ strong bonding capabilities allow them to form a strong structure with concrete or cement, whilst providing superior strength to the construction structures and increasing their longevity.
TMT bars are also devoid of torsional stress as they aren’t put through any physical deformations. Hence, chances of surface defects are almost zero. Reduction in surface defects means that TMT bars are less prone to harmful oxidation, like corrosion, in comparison to TOR steel.
TMT bars are also more affordable when compared to TOR steel. That is because they do not go through additional hardening processes like TOR steel. This in turn reduces energy as well as money spent on deformation processes. Moreover, TMT bars also use 8-11% steel compared to TOR steel and gives longer life to construction structures, as the TMT steel does not react with the concrete, forming rust that occupies more space and makes cracks in the concrete.
TMT BARS ARE IDEAL FOR INDIAN CONDITIONS
TMT bars can be used in various types of construction works due to their amazing flexibility and ductility which TOR steel cannot provide. In a geographically vast and diverse country like India with its hot and humid weather for most part of the year, TMT bars remain the best bet. TMT bars thermo mechanical treatment technology prevents rust and corrosion whereas TOR steel bars contain chloride irons which makes them highly vulnerable in humid conditions.
Further, though both TOR and TMT bars exhibit high strength, TMT bars are significantly more superior and better suited for large concrete construction structures, especially in coastal areas where humidity remains a major issue. Their superior ductile feature also helps to protect construction structures during an earthquake.
If you’re looking to purchase TMT bars, it’s important to understand that the true sense of TMT bars lies in the proper balance between toughness and flexibility. So choosing the right TMT bar will help to begin a new construction on the right note.
There are several grades of TMT bars in the marketplace. The higher the grade, the better the TMT bars are. Herein, Fe 500D Grade TMT Bars offers the perfect balance of strength & flexibility according to IS Standards. Hence, it is recommended for all types of construction purposes. Further, Fe-550 is also extremely flexible in line with the norms laid down.
Top TMT steel bars manufacturer, VINAYAK STEEL LIMITED is a prominent producer and supplier of the best-of-its-kind genuine strongest and long-life TMT steel bar Fe-550, that conforms to IS: 1786:2008 BIS standards (a standard equivalent to a number of international standards like ASTM A615 Grade 60 of the USA; BS 444 Grade 460 of Britain; BST 500 of DIN 488 of Germany).
VINAYAK STEEL’s high-grade Fe-550 is extremely robust with guaranteed assurance of top-notch equilibrium, safety and stability to a concrete structure, allied with the ability to greatly resist dynamic loading with varied yield and tensile strength. In every sense, it remains an ideal construction material for coastal, marine or underground construction structures.
Fe-550 TMT steel bars manufactured by VINAYAK STEEL involve the latest technology with robust quality-check processes including intense anti-corrosion testing methodologies, in extreme rusting conditions. Most importantly, every VINAYAK’s Fe-550 steel bar carries a BIS Certification confirming its adherence to IS 1786:2008 (Contains the Standard Mark, Cast / Lot number, Grade, Size, & Corresponding test results).
To extract the best out of VINAYAK STEEL’s Fe-550, it’s advisable that its best selected in accordance with the design requirement of the construction structure.
VINAYAK STEEL, with its well established in-house infrastructure Capabilities and Capacities plus comprehensive stock of raw material and finished products, is ideally positioned to continually provide the best quality TMT bars for all types of construction needs, for years to come.