In recent times, thermo-mechanically treated (TMT) steel bars have gained popularity in the construction industry. TMT is a process in which the steel bars are subjected to constant and repeated cooling to attain maximum yield strength. These anti-corrosion bars are used for industrial establishments, bridges, residential buildings and all kinds of concrete reinforcement. So, why are TMT bars being preferred to normal steel bars?
Jatin Gupta, CEO, Shree Ji Steel Corporation, told BE, “TMT bar is made of mild steel only. Around 40 years ago, companies used MS-round bars instead of TMT bars. But with time, the popularity of TMT bars has soared. The advantage is that it has a better ductile strength and better binding capacity with concrete. They are specifically designed for earthquake resistant buildings and additionally, possess high thermal resistance.”
The role of steel in any building determines its structural strength and stability. Experts believe that there are several qualities in TMT bars which have made it a preferred steel product for construction. They are high-strength reinforcement bars having a tough outer surface and a soft inner core. As Gupta mentioned, they are not just steel bars with enhanced strength but are also highly ductile and malleable in nature.
When it is manufactured, there is no twisting during the TMT process. Hence, no torsional stress occurs. Surface defects are minimised in absence of torsional stress. Therefore, these bars resist corrosion better than cold, twisted and deformed (CTD) bars or normal steel bars. These bars have also changed the landscape of the construction sector in India, with their versatility and with their ability to be moulded into shapes such as slabs, beams, columns and more.
They also come in different grades making them apt for various structures which include small homes, medium-sized commercial establishments, ports and airports. The grade represents the strength and rigidity of the bar and its yield strength. It is necessary to choose the right grade, depending upon the type of structure.
During the structural design of the structure, the designer selects the appropriate grade based on the structural need, material availability and cost considerations. Most widely used steel grades are Fe415 and Fe500 which provides sufficient strengths for most of the reinforced concrete applications. These bars are neither too expensive nor do they compromise on safety.
The development of TMT bars helped the construction industry in India to mature rapidly. Engineers and architects could experiment with different construction techniques. This led to the development of new solutions for problems earlier encountered by engineers while building tall structures. The recent demand crisis in the market has resulted in some pushback in TMT bar sales.
Gupta told BE, “Presently, there is a lot of fluctuation in prices. In one year, the prices for TMT bars have gone down by `8 and then gone up by Rs 3. Of course, this is the reflection of the slowdown. Small factories are getting shut down these days. Though the government expenditure is good enough, there are various sectors where the government isn’t spending money like in the railways. Along with the public sector, there is also a slowdown in private sectors like real estate. So, we are moving ahead on a lower demand trajectory for TMT bars.”