Reinforcement Steel

Reinforcement plays a very important role in construction taking miost of the tensile forces which act on reinforced concrete structures while concrete takes care of the 

compressive loads. 

Reinforced concrete construction (RCC) faces several  types of environmental attacks during its life time. Chemicals like sulphates and carbonate attack the concrete while chlorides and moisture (water) attack the steel in RCC. It is therefore necessary to take all precautions to prevent such attacks on RCC structures for high  performance. 

The selection of correct type and quality of steel  and its procurement from a reliable source is important. The  success of a RCC job depends to a large extent on the reinforcement being correctly and rigidly fixed in the concrete with the right  spacing and cover. The cover to the reinforcement is extremely important for protection of steel in concrete. The cover should not only be adequate in thickness but the concrete quality in cover itself, should he dense and well compacted. 

Accurate cutting, bending and fixing of the steel bars is a must so that correct cover is maintained and steel is adequately protected. 

Bar Type and Identification 

The reinforcement steel is generally available in three types : 

• Mild steel rounded bars of different grades
• High strength deformed bars of different  grades  and types
• Corrosion Resistant  Steel

While the rounded mild  steel bars arc manufactured by hot rolling of mild steel, the high yield  steel is made by either hot rolling a low  alloy steel or by cold twisting and stretching of nlild steel bar. 

Figure  shows the different  types of reinforcements used. By visual inspection the Engineer can know if the bar is plain  mild steel, hot rolled deformed, cold worked deformed ribbed (TOR) or cold  worked twisted (TOR). 

The cold worked steel is  easily identifiable from its twisted appearance, it may or may not have ribs. 

TOR steel is available and used in our Country. It is available in several types/grades. TOR-40 is identified by a registered  trade mark 'TOR'  on every  meter of bars. TOR-50 is identified by a registered  trade mark as stated above plus mark a '50'  or  '0' or X (star) between the two 'TOR'  trade marks or at times  at  300 mm spacing (See Figure 3). The TOR 50 bars are also painted 'green'  for length of 10 cms at both ends for easy identification. 

Types of  Reinforcement  Presently Used

The pitch of the twist should be between 8 to 12 times  that of nominal diameter of the  bar. The  'red'  paint at the two  ends and in the middle third of the bars indicate defective product and  should not be used in RCC works.