Steel is often used as reinforcement along with concrete and the composite whole is known as reinforced concrete. Concrete has a high compressive strength but a low tensile strength. Thus, concrete fails to expand and
Steel is often used as reinforcement along with concrete and the composite whole is known as
reinforced concrete. Concrete has a high compressive strength but a low tensile strength. Thus, concrete
fails to expand and may develop cracks. On the other hand, steel has both high tensile strength and
compressive strength. The two materials are thus combined to include and take advantage of both these
strengths and take it to a pretty high level. Such a combination helps protect the structure and makes it
safer against heavy loads and seismic forces. The steel bars used along with the concrete are called
reinforcements or rebars.
Concrete in which steel is embedded in such a manner that the two materials act together in resisting
forces is known as reinforced concrete. Rebar or reinforcing bar is the steel bar or mesh of steel wires
that are used as a tension device to strengthen and aid the concrete under tension. Rebar’s surface is
often deformed to promote a better bond with the concrete.
The following checks need to be made before steel reinforcement is done:
The rebar should be cleaned properly
The rebars must be cut and bend properly and precisely.
The steel bars should be free from surface flaws, cracks, imperfect edges and rust. They should
also have a uniform diameter.
Using the same grade and type of steel throughout the structure is preferred.
The quality of steel used for reinforcement works is determined by its mechanical properties like
yield strength, tensile strength, weight, elongation, etc.
A simple test called bend test can be conducted at the construction site to verify the quality of
the rebar. The steel rod is bend to make an angle of 90 to 135 degrees and then straightened.
On doing so, there should be no cracks on it. If the original shape is retained, it is of good
To remedy the problem of low tensile strength of concrete, wet concrete is cast around strong, steel
reinforcing bars, that are tied together to make a cage. When the concrete sets and hardens around the
bars, a new composite material is obtained, called reinforced concrete or reinforced cement concrete
(RCC). This reinforced concrete is capable of working well under both tension and compression: the
concrete resists squeezing and provides the compressive strength, while the steel resists bending and
stretching, providing the tensile strength. The rebars at the bottom of the beam also bear the torsion
and keep the structure safe against bending.
Rebar cages are fabricated and fixed either on or off the project site with the help of hydraulic benders
and shears. The rebars in the cages are connected by spot welding or tying steel wires. Stirrups form the
outer part of a rebar cage and are placed to secure the structural rebar and prevent it from shifting out
of position during concrete placement. Mechanical couplers are also used to connect reinforcing bars
together. Reinforcing bars or rebars are hot-rolled using different steel materials. Different types of
rebars include carbon steel rebars, sheet-metal reinforcing bars, epoxy-coated rebars, European rebars,
stainless steel rebars, galvanized rebars, etc. The cost of rebar is usually estimated on a per-foot basis or
The quantity of steel required for reinforcement depends on the structure where it is being used, and
not on the volume of concrete. It may also vary depending upon the loading conditions. Steel bars of
many shapes and grades are available in the market like mild steel, torsteel, TMT bars, hot rolled steel,
etc. These bars have different specified tensile strengths. For structures in different seismic zones,
different types of steel bars are used.
The main reasons for using steel to reinforce concrete are:
Steel and concrete have approximately the same thermal coefficients of expansion. This helps to
keep the structure uniform during the temperature variations.
Steel is a highly ductile material and can also easily take in tension force in contrast to concrete.
The modulus of rigidity remains same for tension and compression in case of steel.
Steel is easy to use and handle on construction sites. It is recyclable and the combination is also
quite economical and affordable.