As per Table No. 22 of IS:456-2000, we can use following types of reinforcing bars in RCC:-
a) Mild Steel bars conforming to Grade-I of IS: 432 (Part 1)
c) High Yield Strength deformed bars conforming to IS: 1786 (Grade Fe 415 & Fe 500)
Mild steel reinforcing bars are plain, whereas Medium Tensile & High Yield strength bars are Ribbed/ Deformed/ Tor. In modern construction, usually High Yield Strength deformed bars are being used. The High Yield Strength deformed bars manufactures by two processes namely:-
a) Cold twisting
b) Thermo-Mechanical Treatment
The high yield strength was earlier being achieved by raising carbon content and manganese and to a great extent by cold twisting. In larger diameter bars, it is not possible to achieve high yield strength combined with elongation, weldability and bendability by this method. THus, to get all the above properties, technologically advanced technique, namely " Thermo-Mechanical Treatment" is used to achieve higher strength values with low carbon content, in larger diameter bars also.