Structural steel and rebar

Steel enters civil works in two main forms: rolled structural sections and plates for frames, bridges and towers, and reinforcing bars for concrete. Both are made from iron produced in blast furnaces or by direct reduction, refined into steel in converters or electric arc furnaces, and then cast and rolled. Chemistry and processing set strength, ductility and weldability.

Structural steel in India follows IS 2062, with grades named by yield strength such as E250 and E350, and sub-qualities that specify impact toughness for low temperature or thick welded work. Hollow sections, cold-formed sections and high-strength bolts have their own standards. Mill test certificates should accompany every batch, with traceability to the heat number.

Reinforcing bars follow IS 1786, with high-strength deformed bars in grades such as Fe 415, Fe 500 and Fe 550, plus D and S variants that require higher ductility, important in seismic zones. Most modern bars are thermo-mechanically treated (TMT): quenching the hot bar with water hardens the outer rim while the core stays soft and ductile. Ribs on the surface provide bond. Tests include tensile strength, yield or 0.2 percent proof stress, elongation, the ratio of tensile to yield strength, bend and rebend tests and mass per metre. Corrosion protection options include epoxy coating, galvanising, stainless steel bars and simply good concrete cover. Rebar should be stored off the ground, under cover and away from salts, and cut and bent cold to approved shapes.