HYSD bars possess high yield strength than mild steel but TMT bars yields greater tensile strength, flexibility, and ductility than high yield strength deformed bars. TMT bars or Thermo-mechanically treated bars is a technological progression for the production of high strength deformed steel bars for concrete reinforcement. They have a tougher outer core and softer inner core. The high strength of these bars are obtained from thermomechanical treatment wherein the bars get cooled off intensively right after rolling. The quick reduction in the temperature of the exterior layer makes it harder while the interior layer still being hot. The ductility and strength of the bars enhance due to the tempering that takes place due to the heat from the core of the bar. This approach generates a very strong external surface hardened by the steel crystalline formation. The high temperatures and consequent shaping by twisting and rolling effects in the micro-structure unique to the TMT bars.
Advantages of using TMT bars in construction
Thermomechanically treated bars offer excellent weld-ability, great strength workability, healthier elongation, and ductility. Because of their amazing flexibility in construction and renovation, they are suitable for a broad variety of uses. Using TMT bars in construction increases the speed of construction and decreases the cost spent. TMT bars are lightweight when compared to the other alternatives which make the maintenance and transportation of TMT bars more convenient than others. The thermomechanically treated bars depreciates the risk of damage during earthquake, fire and similar natural disasters. The steel of thermomechanically treated bars rods can be recycled without any lack of quality. The steel frames needed for the production can be easily created and compiled in the construction factory itself.
TMT steel bar doesn’t crack or break even after turning and bending 180 degrees. Better elongation and flexibility of the TMT bars are due to the better ductility of the steel. TMT bars with higher elongation rate are easy to transport and gives better cost efficiency when compared to cold twisted deformed bars. For sounder ‘sudden load absorption’ capability, the Fe 500D TMT bars is preferred because of its ductile nature. TMT bars possess high thermal stability and can withstand temperatures varying from 400 to 600 degrees celsius. Thus, they are excellent for resisting fire and implementing safety.
The thermomechanical process gives the bars anti-corrosive qualities. The water cooling procedure for TMT bars resists the formation of coarse carbides in the bars. Absence of surface stresses and coarse carbides makes the bars corrosion resistant. Using TMT for construction thus aids in the longevity of the structure. When considering TMT bars for construction to ensure quality, it is very important to make sure that its bought from a trustworthy manufacturer.
Grades of TMT bars
There are four distinct grades of TMT Steel available in India; Fe-415, Fe-500, Fe-550, and Fe-600. The grade number, yield strength, and tensility are directly proportional. The higher the grade number, the higher the values are.
Below are the areas of uses for different grades of TMT
- Fe 415: RCC Constructions in areas with great corrosion and earthquake incidence.
- Fe 500: RCC constructions, in building, bridges and other concrete structures.
- Fe 550: RCC construction that is exposed to humid coastal, marine or underground areas.
- Fe 600: used for large RCC construction purposes.
Hello everyone ! This is a blog series with two parts and we will be talking about Steel and its properties, TMT bars and TMT Bars Manufacturing Process in detail. So, let’s get started.
The severe earthquake that struck Nepal on April 25, 2015, claimed almost 9,000 lives, many thousands more were injured, and 600,000 structures in Kathmandu and other nearby towns were either damaged or destroyed. The staggering figure of structural damages forces us to believe that it is not the earthquake that kills but poorly built buildings.
The Supreme Court order of demolition of five buildings in Marad, Kerala has come as hot news in media with the people applauding the order as well as a few condemning them. This has not been the first instance of demolition of buildings for illegal construction in coastal lines against the CRZ regulations. Rainbow restaurant, in the banks of Periyar, Aluva also met a similar fate of demolition for illegal construction on CRZ regulations in 2014. Why were these construct to be taken down and what does the coastal regulation zone mean. It has been a question that plagues us.
Over the past few months, a slew of fire accidents has occurred In India damaging human lives, properties and goods. In a tragic incident, 20 students died after a fire broke out in a private coaching center in Surat, Gujarat last month. Eyewitness recall that in a bid to escape the blaze, students were seen jumping and falling from the third and fourth floors of the building. This accident is just one of the countless fire tragedies in the country.
Engineers build leaving a wide berth of safe loading capacity to construct, let’s get a brief view on how the same is for steel reinforcement bars. We have talked enormously on safety codes listed in IS 1786:2008, in the manufacture of reinforcement bars. Now, let’s discuss how safe loads are calculated in a construction material like reinforcement bars. The min. yield strength a reinforcement bar should have is easily inferred from the grade of the reinforcement purchased. Grade Fe 415 having a min. yield strength of 415 N/mm2, similarly for grade Fe 500 having min. yield strength of 500 N/mm2 and Fe 550 with min. yield strength of 550 N/mm2, so goes for every steel reinforcement grade.
We have been talking about the pros and cons of steel and concrete as a construction material. Let’s get a better understanding on why they work better together. Anyone reading about construction materials would have come across the saying – Concrete is good against compression, but weak in tension whereas steel bars are good in tension, but weak in compression. What a few had inferred from the statement is that, steel is naturally weak in the face of compressive forces, which is not the case. Steel is good in both compression and tension. Steel bars or steel reinforcement bars are weak in the face of compressive force due to their dimensional property. Steel reinforcement bars have an insignificant cross sectional area when compared to the length of the steel bars, and thus the ability to withstand compressive forces are naturally less.
Our last blog described the TMT steel bars and its importance as reinforcement for the construction of commercial buildings. More specifically, it described the standard IS 1786:2008 that every reinforced steel bar should conform to. The IS standard defines certain guidelines that must be followed when manufacturing the reinforced steel bar.
The introduction of reinforcement drastically changed the phase of construction of building structures of steel. Reinforced steel provided the necessary tensile strength which the concrete lacks. Today, very few constructions are done without using reinforced cement concrete. At the current scenario, the most used reinforced steel bars are the Thermomechanically Treated (TMT) steel reinforced bars. They are preferred for their excellent tensile strength and optimum ductility. The TMT steel bars are of different grades namely Fe 415, Fe 500, Fe 550 and Fe 600.
When it comes to constructing a building structure, the right set of resources must be used for ensuring the overall life and the integrity of the building. The introduction of reinforcement in construction improved the overall life expectancy of the structure and made them strong enough to withstand the forces of nature. Steel is the primary component used as reinforcement because of its excellent tensile strength, recyclability and similar thermal coefficient of expansion to that of concrete.