IS 1786 — TMT Steel Bars

IS 1786:2008 — 'High Strength Deformed Steel Bars and Wires for Concrete Reinforcement - Specification' is the Indian standard for HYSD (High-Yield Strength Deformed) steel bars used in RCC construction. Published by BIS, the current edition is IS 1786:2008 with multiple amendments through 2024. The standard covers chemical composition, mechanical properties, surface deformation patterns, dimensional tolerances, and test methods for steel bars in diameters 6 mm to 50 mm.

Key IS 1786 specifications: (1) Steel grades — Fe-415 (yield strength 415 MPa), Fe-500 (500 MPa), Fe-500D (ductile, fy 500 with elongation ≥ 18%), Fe-550 (550 MPa), Fe-550D (ductile, 550 + ductility), Fe-600 (600 MPa). (2) Mechanical properties — yield strength (0.2% proof or upper-yield), tensile strength, elongation on 5.65√A gauge length, bend test. (3) Chemical composition — limits on carbon, manganese, phosphorus, sulphur, plus combined chromium + nickel + copper for high-strength grades. (4) Surface deformation pattern — rib / lug pattern for bond with concrete; specified in Annex C. (5) Dimensional tolerances — mass per unit length within ±3% (for bars >12 mm) to ±7% (for bars ≤ 8 mm). (6) Test methods — tensile, bend, re-bend (after ageing).

Before 2008, IS 1786 was published in multiple editions (1985, 1993). The 2008 revision introduced the Fe-500D, Fe-550D ductile variants — ductile rebar with elongation ≥ 18% and tensile-to-yield ratio ≥ 1.10 — required by IS 13920 ductile detailing for SMRF in Zones III/IV/V. Modern Indian construction predominantly uses Fe-500 (residential, commercial), Fe-500D (seismic frames), and Fe-550 (high-rise). Fe-415 is rarely produced by major mills; Fe-600 is reserved for specialty applications. Site QC priorities per IS 1786: visual inspection for surface deformation pattern, dimensional verification (mass per metre), tensile testing of consignment samples, mill test certificate verification.