Getting to know the rods
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Not much general attention is given to the quality aspect of steel, though it is an important part of most structures.
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– Photo: H. Vibhu
BACKBONE: Quality should be an important consideration when it comes to selecting steel for construction.
While steel is an integral part of construction, not many are aware about the kind of steel that needs to be used for it. The layman only knows that it should be ‘good’ steel. While branded items are flourishing in the market, there are a number of local manufacturers who are trying to compete, especially during the boom period.
Building material
As a building material, it is one of the most important items and should be seen on par with cement in terms of quality. However, this material, because of the lack of visibility from outside, does not find much of a place in the layman’s mind. A person takes pains to see whether the concrete mix is in the right proportion or whether his house is getting a good coat of paint or whether quality woodwork is being done. But, steel, which gives the basic strength to a building in combination with concrete actually does not draw much attention unless its availability is affected like it had happened some five years ago.
A large section of people are ignorant about the need to check the quality of steel. Not that it is easy to check. It needs to be checked at an analytical laboratory or one has to depend on the engineer’s advice on its quality. The steel used in construction sector is usually double the strength of other steel available in the market.
Branded steel is more known to people. But the availability of this steel is rather scarce, said S. Suresh, structural engineer. The locally available steel may not be having the top quality of the big brands, but they are vastly used in construction here because of easy availability and their being cheaper than the top brands by at least Rs.2 to Rs.3 a kilo.
While the top brands have a commanding market presence and are used by many major builders, the local brands have also moved up by making available products that have an ISI mark.
The potential of the steel market is huge, considering the scale of the construction works that are going on now, said Paul Varghese, promoter of Metrolla Steels Limited, which produces Metcon Steel. The consumption of steel can be roughly said to be around 3000 tonnes a day, he said.
Steel is the backbone of a building, giving it the desired look as envisaged by an architect, said Mr. Varghese. People need to be careful about the quality of steel used as it cannot be removed, when once used. New plaster can be applied but not new steel, he said. The locally made steel may not be having all the basic elements in the correct chemistry, but that would not affect its strength per se, said Mr. Suresh. It may, however, affect the durability if it is not properly embedded in concrete. The technical skill in giving the right concrete cover is very important, he added.
Ductility
Another quality that needs to be ensured is ductility, he said. The thermo mechanical treated (TMT) steel is more ductile than the cold twisted deformed (CTD) bars. The CTD bars, which are mechanically processed are said to be less strong than the TMT bars, because of the treatment that adds strength to the steel rods.
Ductility of steel is important during seismic vibration. To be ductile means having the physical property to elongate. Usually steel is ductile, but top quality steel will have better ductility.
During mild earthquakes, if the steel is able to elongate, the structure will develop only cracks.
SHYAMA RAJAGOPAL
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