Difference between TMT Bar and TOR Steel
Steel bars are integral part for all type of construction that is used to reinforce the concrete. In construction, steel bar is the most important material because it is not only reinforcing the concrete but also saves the construction from easy wear and tear due to rust or any natural calamity such as an earthquake.
Here we will discuss about the different types of steel bars that are of different categories. Generally the property and type of steel bars varies depending on the geographical and environmental factors. In present days’ construction technology prefers to use TMT bars in construction but before it, till 90’s CTD or TOR steel were used vastly.
TOR stands for Toriseg Steel Corporation of Luxembourg. It refers to a brand name. The name became so popular that TOR became synonymous with CTD or Cold Twisted Deformed steel bars. During the time period seventies to nineties, TOR steel was used for reinforcement purposes of the construction massively. Thereafter, TMT bars introduced to the market.
For superior ductility and other qualities TMT Rebar gradually captured the market over TOR Steel & CTD. TMT bars or Thermo Mechanically Treated bars are considered as high-strength reinforcement bar with excellent corrosion-resistant property. Even TMT bars have many grade classifications as well. It comes with different grades such as Fe 415, Fe 500, Fe 500D, Fe 550D, Fe 600 etc. Here the word ‘D’ signifies ductility which provides the steel bars a higher percentage of elongation.
Though TOR and TMT bars are both high strength reinforcement steel bars, engineers prefer the TMT bars most because of its superior ductility. Conventional TOR steel is less ductile and other features are poor for which reason TMT bars are used for every kind of concrete construction.
i.e. from residential building, highway, sports complex, bridges, dams, factories or industrial establishments and retail purposes as well. Being completely residual stress free, TMT bars are highly corrosion and Fire resistant as well.
Before the introduction of TMT Steel Bars to the market TOR steel was a huge upliftment from mild steel bars. It was better high-adherence steel at that time and had more tensile stress than anything else. These were produced from mild steel billets with limited carbon content. Their high elasticity value comes from the surface deformation created by twisting the steel after elongation. But this feature created residual stress into that as well, which used to make the bars corrosion-prone.
TMT steel bar has upgraded the variety for construction purposes. These Thermo Mechanically Treated bars avoid twisting operation and thus cut down residual stress to increase the corrosion resistance.
In geographically diverse country like India, engineers’ first choice is always TMT bar as its Thermo Mechanical Treatment technology prevents rust and corrosion in humid weather conditions whereas, TOR steel bars contain chloride irons which makes it very much vulnerable in humid conditions. Though both TOR and TMT bars exhibit high strength, TMT bars are significantly much superior and better suited for use in large concrete structures, especially on coastal areas where humidity is a major issue and also its superior ductile feature helps to protect the construction structure during an earthquake.
As mentioned earlier, TMT bars have different grades as well. We all demand strength in TMT bars for our home but before purchasing TMT one must know that true sense of TMT lies within proper balance between toughness and flexibility. So choosing the TMT bar wisely is very basic part before starting a new construction. There are several grades of TMT bar like Fe 415, Fe 500, Fe 500D, Fe 550D, Fe 600 etc.
Fe 500D has 0.25% Carbon (max) as compared to 0.30% (max) in Fe 500. Also the maximum percentage of Sulphur and Phosphorous are lower in Fe 500D. Fe 500D with lower amount of carbon, sulphur and phosphorous helps in preserving the steel and resisting from earthquake shocks in future.
Therefore, as per IS 1786:2008 amongst all the grades of TMT Bar Fe 500D has the perfect combination of strength & flexibility in it.
So it saves the construction from calamities in high earthquake prone areas. Due to the ductile micro-structure and hard exterior surface, TMT bars have a stronger external layer and higher tensile strength. Thus, TMT bars provide a longer life to the structures where these are used in construction. So before purchasing TMT, know well the difference between TMT and TOR steel bars and understand why it is beneficial to opt for TMT bars over other variants.
