infrastructure boom to support rebar demand in india...
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- SteelworldResearch Team
32 January 2020STEELWORLD
Infrastructure boom to supportrebar demand in India
Reinforcement steel
bar (rebar) is a steel
bar or mesh of steelwires
used in reinforced concrete
and masonary structures to
strengthen and hold the
concrete in tension. The
surface of rebar is often
patterned to improve the
quality of the bond with the
concrete.
Reinforcing bars in
masonry construction have
been used since at least the
15th century (2,500 meters
of rebar was used). During
the 18th century, rebar was
used to form the carcass of
the leaning tower of
Nevyanskin, Russia, built on
the orders of the
industrialist AkinfiyDemidov.
The cast iron used for the
rebar was of high quality,
and there is no corrosion on
the bars to this day. The
carcass of the tower was
connected to its cast iron
tented roof, crowned with
one of the first known
lightning rods. However, it
was not until the mid-19th
century that rebar displayed
its greatest strengths with
the embedding of steel bars
into concrete, thus
producing modern
reinforced concrete.
The need
Rebar's surface is often
"deformed" with ribs, lugs or
indentations to promote a
better bond with the
concrete and reduce the risk
of slippage. The most
common type of rebar is
carbon steel, typically
consisting of hot-rolled
round bars with deformation
patterns. Other readily
available types include
stainless steel, and
composite bars made of
glass fibre, carbon fibre or
basalt fibre. The steel
reinforcing bars may also be
coated in an epoxy resin
designed to resist the
effects of corrosion mostly
in saltwater environments,
but also land based
constructions.
Bamboo has been shown
to be a viable alternative to
reinforcing steel in concrete
construction. These
alternate types tend to be
more expensive or may have
lesser mechanical
properties and are thus
more often used in specialty
construction where their
physical characteristics fulfil
a specific performance
requirement that carbon
steel does not provide. Steel
and concrete have similar
coefficients of thermal
expansion, so a concrete
structural member
reinforced with steel will
experience minimal
differential stress as the
temperature changes.
Rebar is required to
compensate for the fact that
whilst concrete is strong in
compression, it is relatively
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34 January 2020STEELWORLD
weak in tension. By casting
rebar into concrete, it is able
to carry tensile loads and so
increase overall strength.
Steel reinforcement steel
bars that are provided in
combination with plain
cement concrete to make it
reinforced concrete. Hence
these structures form steel
reinforced cement concrete
structure (RCC).
Plain concrete is weak in
tension and strong in
compression. Tensile
property for concrete
structures is obtained by
incorporating steel
reinforcement which is
strong in both tension and
compression. The tensile
property provided by the
steel reinforcement
prevents and minimizes
concrete cracks under
tension loads. The
coefficient of thermal
expansion of steel
reinforcement and concrete
are similar in that they
undergo similar expansions
during temperature
changes.
This property will ensure
that the concrete is
subjected to minimal stress
during temperature
variations. The surface of
the steel reinforcement bars
is patterned to have a proper
bond with the surrounding
concrete material. The two
main factors that provide
strength to the concrete
structures are steel and
concrete.
The design engineer will
combine both the elements
and design the structural
element such a way that the
steel resists the induced
tensile and shear force,
while the concrete takes up
the compressive forces.
Use of high-quality
reinforcement steel
products in concrete
improves its properties.
Nowadays, reinforcement
steel products are some of
the most important
building materials used in
metal industry.
It is impossible to
imagine buildings or metal
constructions without
reinforcement steel. Thanks
to their excellent
performance and technical
properties, reinforcement
steel products are being
used in all fields of
construction. Choosing
quality steel rebars and coils
is a very important and
responsible task at the first
stage of construction.
The durability, safety
and service life of buildings
directly depend on the
quality of reinforcing
materials. Rebars may be
categorized by their profile:
there are round, smooth
and ribbed.
Nowadays, reinforced
concrete is being used on
almost all construction
sites, and it is one of the
predominating building
materials.
Steel rebars are a very
important component of
monolithic reinforced
concrete, as they improve
the concrete and reinforced
concrete construction
bending and shear behavior
and strength. The most
commonly used reinforcing
steel materials are flexible,
including rebars, welded
wire mesh and frames.
Nowadays, reinforced
concrete is being used on
almost all construction
sites, and it is one of the
predominating building
materials.
Types of rebars and their
applications
Steel is only used as
rebar because elongation of
steel due to high
temperatures (thermal
expansion coefficient)
nearly equals to that of
concrete. The surface of the
mild steel bars is plain and
round in shape. They are
available in various sizes of
6 mm to 50 mm. They are
used in concrete for special
purposes, such as dowels at
expansion joints, where bars
Nowadays,
reinforced
concrete is
being used
on almost all
construction
sites, and it is
one of the
predominating
building
materials.
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35 January 2020STEELWORLD
must slide in a metal or
paper sleeve, for contraction
joints in roads and runways,
and for column spirals.
They are easy to cut and
bend without damage.
Deformed steel bars
have ribs, lugs and
indentation on the surface
of the bar, which reduces
the major problem that is
faced by mild steel bar due
to slippage and good
bonding is achieved
between concrete and rebar.
The tensile property is
higher compared to other
rebars. These bars are
produced in sections from 6
mm to 50 mm dia.
Thermo mechanically
treated bars are hot treated
bars that are high in
strength used in reinforced
cement concrete (RCC)
work. It is the latest
induction in the mild steel
bars with superior
properties such as strength,
ductility, welding ability,
bending ability and highest
quality standards at
international level.
High strength deformed
bars are cold twisted steel
bars with lugs, ribs,
projection or deformation on
the surface. It the
extensively and majorly
used for reinforcement
purposes in a construction.
These bars are produced in
sizes or sections from 4 mm
to 50 mm in diameter.
European rebar is made
of manganese, which makes
them bend easily. They’re
not suitable for use in areas
that are prone to extreme
weather conditions or
geological effects, such as
earthquakes, hurricanes, or
tornadoes. The cost of this
rebar is low.
As the name represents,
it is made up of carbon steel
and is commonly known as
Black Bar due to carbon
colour. The main drawback
of this rebar is that it
corrodes, which adversely
effect the concrete and
structure. The tensile
strength ratio coupled with
the value makes black rebar
one of the best choices.
Epoxy-coated rebar is
black rebar with an epoxy
coat. It has the same tensile
strength, but is 70 to 1,700
times more resistant to
corrosion. However, the
epoxy coating is incredibly
delicate. The greater the
damage to the coating
indicates the less resistant
to corrosion.
Galvanized rebar is only
forty times more resistant to
corrosion than black rebar,
but it is more difficult to
damage the coating of
galvanized rebar. In that
respect, it has more value
than epoxy-coated rebar.
However, it is about 40%
more expensive than epoxy-
coated rebar.
Glass-Fiber-Reinforced-
Polymer (GFRP) is made up
of carbon fibre. As it is
made up of fibre, bending is
not allowed. It is very
resistant to corrosion and
is costly when compared to
other rebars.
Stainless steel rebar is
the most expensive
reinforcing bar available,
about eight times the price
of epoxy-coated rebar. It is
also the best rebar available
for most projects. However,
using stainless steel in all
but the most unique of
circumstances is often
overkill. But, for those who
have a reason to use it,
stainless steel rebar is 1500
times more resistant to
corrosion than black bar; it
is more resistant to damage
Stainless steel
rebar is the
most expensive
reinforcing bar
available, about
eight times the
price of
epoxy-coated
rebar.
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36 January 2020STEELWORLD
than any of the other
corrosive-resistant or
corrosive proof types or
rebar, and it can be bent in
the field.
Hot rolled deformed
bars are most commonly
used steel reinforcement
for RCC structures. As the
name says, the hot rolling
of the reinforcement is
undergone leaving certain
deformations on its surface
in the form of ribs. These
ribs help to form a bond
with the concrete. The
typical yield strength of hot-
rolled deformed bars is
60000psi.
A cold worked
reinforcement bar is
obtained by letting the hot
rolled steel bars to
undergo cold working. In
the cold working process,
the bars will undergo
twisting and drawing. The
process is performed at
room temperature. The
cold worked steel bars do
not undergo a plastic yield
thus has less ductility
when compared with hot
rolled bars.
Production and
consumption of rebars in India
Rebars have become the
preferred standard for
construction of private or
commercial building
structures, bridges and
many other business
structures for public or
private uses. The most
popular among them is the
thermo mechanically
treated (TMT) reinforced
bars. About 35% of the total
steel production in the
country was accounted by
the reinforced steel industry.
Usage of high strength
TMT steel rebars has
ensured rapid growth within
the construction sector.
India produces around 30
million tonnes of rebars
annually which are
consumed fully. Of late,
however, the slowdown in
infrastructure sector has hit
rebar industry as well with
both production and
consumption declined over
the last few years, albeit
marginally to create surplus
in the system.
Leading manufacturers,
meanwhile, have lowered
operating capacity to
control production and
thereupon, supply to suit
India’s domestic demand.
Many producers of rebar
have started selling under
branded product to fetch
premiums other such
products available.
Outlook
The outlook of rebar
manufacturers is bright
considering huge
infrastructure push initiated
by the government with a
massive fund allocation
plans to push construction
of bridges, modernising
railway stations and
creating additional handling
capacity of national
highways and airports.
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Usage of high
strength TMT
steel rebars
has ensured
rapid growth
within the
construction
sector.
In-Focus
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