WHY REBARING IN CIVIL CONSTRUCTION

RCC Construction

                            Francois Coignet, a French industrialist built a four storey house in Paris with reinforced cement concrete in 1853. That was first ever attempting to build using reinforced cement concrete in modern history. Since then the technology has evolved with one of highest buildings in the world being built using RCC.Reinforced Cement Concrete is a composite material with excellent strength and durability characteristics. Like clay concrete could be moulded into any shape, of any scale by using suitable moulds (or formworks as they are called). Concrete could be made anywhere by mixing its constituents in suitable proportion. It slowly develops the strength over a reasonable period of time, just sufficient to facilitate onsite operations. This portable nature of concrete along with the strength it develops is the key to its popularity.

 Why rebar in RCC construction

                      Concrete on its own has got excellent strength when pressed against anything. However on pulling (or applying tensile forces) it easily gives way.

                      Steel rounds (with suitable embossing to facilitate bonding with concrete) are deterministically embedded in concrete to impart desired strength. Beauty of steel rebars is that they can take both tensile as well as compressive loads. In RCC columns you would find steel rebars carrying bulk of compressive loads. Steel & concrete have got similar temperature coefficients, making them expand/contract together and help the bonding.

 How to judge a rebar

• Consistency of physical properties across the rebar length
• Better ductility
• Lower impurities
• Easy to work with (during fabrication)
• Bond with concrete

Necessity of Rebaring Technique in Reinforced Concrete Construction

The steel reinforcement mostly is divided into two categories i.e.

• Primary Reinforcement or Main Steel reinforcement
• Secondary reinforcement or distribution reinforcement

Main steel reinforcement bars are employed in R.C.C structures to ensure resistance against the whole design loads coming over it. The secondary reinforcement bars are mainly employed due to durability as well as for aesthetic reasons.

This reinforcement guarantee resistance for localized areas, like limited cracking. These also offer resistance against the stresses that are created due to temperature variations.

The main bars employed of specified diameter are bent at the ends. The stirrups are reinforcements that are provided laterally, to keep the main bars of the structural elements like beams and columns, in position.

The stirrups may be circular, square, rectangular, helical or diamond shape based on the cross-section of the structural element. The reinforcement bars in the corners may be L – shaped.

The caging for the structural element under consideration must be properly tied, so that during concreting no bar is disturbed from its position. This is a check to be always kept in mind during concreting, else it is a threat to the durability of the structural member.

The rebars are mainly provided at the junctions where the formwork of the structural element is closed as well as at the point where a new structural element needs to be bond with the former one.

Equipments used for Rebaring Techniques

The equipment that is used for rebaring operations is developed with time, as the size of bars is increasing. Larger size bars are difficult to be handled by hand operation.

                The usage of chisel and hammer was an earlier practice used for bar bending. The bar is held fixed with the help of three thick bars over a bar bender bench. Then the bending is done by means of manual force, operated with the help of levers. To tie the rods, cutting pliers were used, and tied by steel wires.The enormous demand for work and bars with large diameters have made to depend on machines for bar bending. This improved method helps in reduction of time consumed by an ordinary method.