The TMT bars are abbreviated as Thermo Mechanically Treated bars. They are also called as Reinforcing bar or Rebar in Civil engineering terminology. These bars are used for providing the tensile strength to the structure which provides equilibrium for the compressive strength provided by concrete.
The TMT bars comes often in different grades for which they are selected according to the design requirement of the building. They are as follows.
*The symbol ‘Fe’ denotes ‘Ferrous’ and the number following Fe indicates the specified minimum 0.2% Proof Stress or Yield stress in N/mm2. The letters ‘D’ and ‘S’ indicates the same specified minimum 0.2% proof stress or Yield strength in N/mm2 with some enhanced and additional requirements.
The TMT bars comes in various diameters like 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 16mm, 20mm, 25mm, 28mm, 32mm, 36mm, 40mm, 45mm, 50mm.
Generally, for house construction of up to G+5 buildings, the general rebar diameters used for various parts of structures are as follows.
Mat Reinforcement. – 10mm, 12mm.
Pedestal Reinforcement – 12mm, 16mm.
* The above-provided details are just for understanding. The actual reinforcement detail may vary according to the structural requirements.
Columns generally contain the diameters as 12mm, 16mm, 20mm, 25mm as the main reinforcement in vertical direction and 8mm, 10mm diameters as stirrups in a horizontal direction. Sometimes different diameters are also used in combination for main reinforcements in columns.
Plinth beams have 10mm, 12mm in main reinforcement and 6 mm or 8mm as stirrups.
Beams will have reinforcement connecting to column reinforcement. Generally beams reinforcement can be categorized into Top Reinforcement and Bottom Reinforcement and out of which the bottom reinforcement is the most important one.
Top reinforcement generally consists of 12mm, 16mm whereas the bottom reinforcements sometimes consist of 12mm, 16mm, 20mm, 25 mm as well. The stirrups will be 8mm or 10mm.
The slab will have reinforcement with diameters 10mm and 12mm maximum. The reinforcement in the slab might be either in one direction or in both directions depending on the design consideration whether it is a One-way slab or a two-way slab respectively. The stirrups of the same will be having a diameter of 8mm majorly.
Staircase or Ramp:
The staircase has reinforcements for both Steps (Rise and Thread) and the Ramp (slope) of the staircase. The Ramp will contain 12mm or 16mm and for the steps (Rise and Thread) the reinforcement will be of 10mm or 12mm. The handrail or the parapet in case of a ramp contains 10mm reinforcement bars.
Checks before choosing Reinforcement:
1. Every steel bar contains the name of the manufacturer, the grade of the bar, traceable identification and Standard Mark as per the Bureau of Indian Standards specifications.
2. Check for rust free rebar which is really good for construction.
3. Every Purchaser has a right to get the certificate from the manufacturer or supplier in case the bars/wires have not been inspected at the manufacturer works which contains the process of manufacture and test results sheet signed by manufacturer giving the results of each mechanical test applicable and also the chemical composition for the material purchased.