As you already know, the cement concrete is quite strong in compression but is weak in tension.
Providing steel bars as Reinforcement is an ingenious solution which takes care of the weakness of concrete and makes it strong.
RCC is a concrete strengthened with the use of steel bars.
An advancement in RCC has resulted into the Prestressed concrete.
This article brings to you the working knowledge about reinforcements in a simple-to-understand language.
Types of steel bars:
There are two types of steel bars used for reinforcement.
Mild steel bars of grade Fe250 and
Ribbed or Torsteel bars
(Also known as HYSD , High yield strength bars.)
HYSD bars are available in Fe415, Fe500 & Fe 550 grades.
The grade of bars specifies the ultimate tensile strength of the bars and is expressed in N/Sqmm.
( 1 N/sqmm.= 10kg/sqcm).
Thus for a grade 500 bar the UTS shall not be less than 500 N/sqmm or
Connecting two bars:
1.The steel bars are connected to each other by mild steel wire known as binding wire. This comes in 16 gauge(1.6mm diameter).
2.Another method is to weld the bars at the nodal points. How ever, due to the difficulty in organizing welding at site , in smaller projects binding wire method is only used.
When two bars are to be connected for extension in lengths,second bar is lapped with the first bar for a certain length called lap length which is generally specified as follows:
For vertical bars: 45D( column, wall)
For horizontal bars: 60D( slab,beam)
Bar splicing can also be done with threaded connectors. In that case the bars are to be threaded. This method is not yet popular for residential projects.
The reinforcement must be laid or fixed in such a way that a specified distance is maintained between the outer surface of the concrete & the steel bar.
This distance is known as cover. Following values are specified for moderate exposure conditions:
Cover blocks of mortar or PVC are available for different widths .Using these blocks ensures that specified cover distance is maintained.
Cutting length of bars:
It is the length of bars which when cut, bent & placed in the concrete maintains the specified cover .
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