HISTORY For year’s, Bamboo has been used by man for construction activities, later it has been replaced by CTD (Cold Twisted Deformed steel rods) or TOR steel rods. The manufacturers adopted the Cold Twisting Process in which the naturally cooled rods were twisted by means of motors. Thus the molecular structure of the core steel is weakened. Thus it should not be used for construction activities. Now, the TMT (Thermo Mechanically Treated) steel bars have emerged. Description TMT Bars, Thermo mechanically treated bars are high strength deformed steel bars used in reinforced cement concrete (RCC) work manufactured with the help of advancement of technology. TMT bars are latest production in MS steel bars and have superior properties such as strength, ductility, welding ability, bending ability and highest quality standards at international level. Technical Specification Chemical Composition Constituent Percent, Maximum Fe 415 Fe 415D Fe 500 Fe 500D Fe 550 Fe 550D Fe 600 Carbon 0.30 0.25 0.30 0.25 0.30 0.25 0.30 Sulphur 0.060 0.045 0.055 0.040 0.055 0.040 0.040 Phosphorus 0.060 0.045 0.055 0.040 0.055 0.040 0.040 Sulphur & Phosphorus 0.110 0.085 0.105 0.075 0.100 0.075 Nominal Cross - Sectional Area And Mass S.No. Normal Size (mm) Cross Sectional Area (mm) Mass per meter (kg) Permissible Tolerance for individual Sample 1 8 50.3 0.395 -7% 2 10 78.6 0.617-7% 3 12 113.1 0.888 -5% 4 16 201.2 1.580 -5% 5 20 314.3 2.470 -3% 6 25 491.1 3.850 -3% 7 28 615.8 4.830 -3% 8 32 804.6 6.310 -3%