1. Manufactured by Steel Brands, Zimbabwe

2. What are TMT Bars ? TMT – Thermo Mechanically Treated Bars
High strength reinforcement bars in different strength grades
BS – 4449 (1997), Gr. 460 and ASTM A615, A706, Gr. 460 which achieve their properties by on-line thermo processing

3. TMT Bar Usage
Areas where TMT Bars are being suitably used because of High strength & Corrosion resistance properties
Bridges
Fly-overs
Multi – Storied Buildings
Concrete Roads
Underground Construction
Dams
Industrial structures
Marine structures
And of course your SWEET HOME

4. Product Characteristics of TMT BARS
Chemistry
As per IS: 1786/’85
In Production of TMT bars, Carbon content is restricted to below 0.25% for better Ductility, Bend- ability and Weld-ability.
Carbon % Max.
Sulphur % Max.
Phos. % Max.
S+P % Max.
Fe-460
0.25
0.060
0.11
Fe-500
0.055
0.105
Fe-550
0.050
0.10

5. Properties
Mechanical Properties of TMT Bars as per IS: Grade BS
Yield Stress (N/sq.mm) 469
Tensile Strength (N/sq.mm) 506
Elongation minimum 14% (Av. 18%)
Required Steel Composition Grade BS
Max. Carbon – 0.25 % (for 10mm to 25 mm bars)
Max. Sulphur %
Max. Ph ,06 %
Manganese % to 0.8 %

6. Micro – Macro Structure
Microstructure of TMT bar Tempered Martensite Rim Ferrite Pearlite Core

7. Comparison of Mechanical properties of TMT BARS with Conventional Bars
Re-bar Quality
IS:1786 conventional re-bars
TMT BARS
Grade
Fe-415
Fe-500
Fe-550
Fe-460
Yield Strength, Mpa Min.
415
500
550
460
UTS, Mpa Min.
485
545
585
580
630
Elongation, Min.
14.5 12 8 22 20 18
Bend up to, Min. 3d 4d 5d 2d

8. Special Features of TMT BARS
Higher Strength combined with higher elasticity (elongation) as compared to other re-bars
Excellent weld-ability
Resistant to fire hazards
Excellent Ductility
Higher Fatigue strength
Easy work-ability at site
Fulfills bonding requirement with Concrete
Fulfills all requirements of BS

9. Advantages of Producing TMT BARS
Reduction in secondary scale losses
Lower cost of production
Less manpower requirement
No off-line processing, hence, bars are ready for dispatch
Lower inventory
Product value addition

10. Customer Requirements
Lower construction Costs due to Higher Strength combined with better elongation
Reduction in total weight of reinforcement bars requirement
Earthquake Resistance
Better corrosion resistance
Heat Resistance
Better weld-ability
Easy availability of better material

11. Advantages of Using TMT BARS
Savings in steel consumption
Reduction in civil construction cost
Better Safety of Civil Structures
Resistant to earthquakes
Resistant to fire hazards
Better Corrosion Resistance properties
Easy working at site owing to better Ductility & Bend-ability
Good Weld-ability

12. Comparison of TMT Bars with CTD Bars
Properties
CTD Bars
TMT Bars
Strength
Maximum up to Grade Fe-415
Grades of Fe-460, Fe-500 & 550 are easily available.
Elongation
(Elasticity)
As per IS: 1786/’85
Elongation achievable more than 50% in comparison to CTD Bars.
Weld-ability
Preferably avoided as welded joints are weak.
Better and no loss of strength.
Formability
Bend 3D – 5D, Re-bend 5D – 8D.
Excellent due to uniform elongation. Bend 1D, Re-bend 4d
Ductility & Fatigue Strength
High
Higher than CTD bars hence most suited for earthquake resistant structures.
Fire Hazards
Loss of Strength on temperature rise.
Negligible loss in strength up to 500 deg. C.
Corrosion Resistance
Scales fall down during cold twisting.
Better Corrosion resistance.
Overall Economy
Lower Costs & Faster working.

13. Weight & Cost Savings of TMT BARS
CHARACTERISTICS
CTD 415
TMT 460
TMT 50
DESIGN STRENGTH
415 N/sq. mm.
460 N/sq. mm.
500 N/sq. mm.
QTY. REQUIRED
1.000 MT
0.854 MT
0.809 MT
% of SAVING IN WT. OVER CTD 415
14.6 %
19.15 %
SAVING w.r.t. CTD 415 / MT
US$ 15
US$ 25
% of SAVING w.r.t. CTD 415
6.8 %
12.0 %

14. Additional cost saving by using TMT BARS with welded joints
Type of Lap
Lap Length required
Material Requirement
% Cost saving per joint/bar
Conventional based on concrete steel bonding.
Avg. 50 dia.= 1000 mm
lw = 50 D
2.47 kg. Of Bar
For Welded lap joints
6.3 dia. = 126 mm
lw = 6.3 D
0.31 kg of Bar
65%

15. Savings by using TMT BARS
Section
Grade of Concrete
Grade of Steel
Qty. in Kg.
% of Saving in Cost over
fy-250
CTD-415
AXIALLY LOADED COLUMNS 20
302 -
189
32%
TMT-460
169
39%
10.4%
UNIAXIAL BENDING WITH COMPRESSION
115 76
28% 70
34% 8%

16. Some typical Examples of Savings depending on structural design
Office Building:
Total Saving 12.8%
Hotel:
Total Saving 14.1%
House:
Total Saving 11.9%
Industrial hall:
Total Saving 13.6%

17. Thermo mechanical treatment process
After Finishing stand, bar passes through Quenching system and receives a short /intensive cooling of the surface.
Surface of bar is converted to hard martensite structure while core remains austenitic.
The core re-heats the quenched surface and tempers the external martensite.
The surface and core temperatures become equal. This is called the Equalizing temperature.
On further cooling on the cooling beds, the remaining austenite transforms into a fine grained pearlite structure.

18. Schematic layout of quenching plant
From Cold Water Sump
Gate Valve
Cold Water H.P. Pump House
High Pressure Header
Ball Valves
Finishing Stand
Pinch-Roll
Quenching Box
Flying Shear
Compressed Air Line
Cooling Bed

19. Special Safety Features of TMT Bars
Earthquake Resistance
Heat Resistance
Corrosion Resistance

20. Earthquake Resistance properties of TMT bars
TMT bars have high fatigue resistance due to their high ductility. This feature makes them most suited for Earthquake resistant structures and equipment foundations.

21. Requirements for earthquake resistance
Stiffness
Strength
Ductility

22. Concrete Homes Reinforced Concrete Homes Stand Up to Earthquakes
Built according to good practices, concrete homes can be among the safest and most durable types of structures during an earthquake. Homes built with reinforced concrete walls have a record of surviving earthquakes intact, structurally sound and largely unblemished.
In reinforced concrete construction, the combination of concrete and steel provides the three most important properties for earthquake resistance: stiffness, strength, and ductility.
Why reinforced concrete is safe?
Reinforced concrete walls are a composite system: Concrete resists compression forces, and reinforcing steel resists tensile forces produced by an earthquake.
The concrete is cast around the bars, locking them into place. The exceptional ductility of the steel to resist tensile forces, coupled with the rock-like ability of concrete to resist compression, results in an excellent combination of the three most important earthquake resistance properties: stiffness, strength, and ductility.
Studies have shown that properly designed reinforced concrete walls offer greater earthquake resistance than other types of construction.

23. TMT Bars for Earthquake Resistance
For Earthquake Resistance structures need to be provided with balanced Stiffness, Strength& Ductility between its members, connections & supports.
TMT Bars provide very high strengths with comparatively higher Elongation Values along with better Ductility as compared to other Rebars.
Better Weld-ability of TMT Bars helps in making high strength connections with other sections with little overlap.
“A Chain Breaks at its Weakest Link”

24. Stress-Strain Curves

25. Comparison of % Strain for TMT bars & CTD bars

26. Need for Earthquake-Resistant Buildings
Stable Ground
Good foundation
High Grade Cement
Reinforcing Material
Reinforcing Steel
CTD bars/ TOR Steel
TMT Bars
Inherent Qualities of TMT Bars:
High Ductility & High Elongation
High Fatigue Resistance to Dynamic / Seismic Loading
High UTS / Proof Stress Ratio

27. Heat Resistance Properties of TMT BARS
In TMT bars, test results have shown no loss of strength up to 500 deg. C. In the temperature range 550 to 600 deg. C, the Yield strength decreases by 20 N/ sq. mm. Only.
Hence TMT bars can be used in places prone to fire hazards.
In CTD bars there is a large loss of strength at elevated temperatures.

28. Effect of Temperature increase on Yield Point

29. Corrosion Resistance Properties of TMT BARS
Corrosion Tests indicate that TMT Bars are comparatively less prone to corrosion than cold twisted deformed bars.
In TMT Bars the protective layer of scale, which normally falls down during cold twisting, protects against corrosion. Moreover, stress corrosion is also avoided in TMT bars as internal stresses are absent as compared to CTD bars.

30. Various Corrosion Tests

31. Conclusion: Suitability of TMT Bars in Hill Architecture
Higher Yield Stress to UTS Ratios
Higher Elongation
Earthquake Resistance
Heat Resistance
Weld-ability

32. I used Conventional Bars
I used NEXUS TMT