Comparison of reinforced concrete and prestressed concrete

Welcome to our presentation
Topic: Comparison of Reinforced Concrete and
Prestressed Concrete
Presented By:
Md. Estiak Hossain Shuvo
Daffodil International University
E-mail: spiceshuvo5683@gmail.com
Department of Civil Engineering

• What is a Reinforced
Concrete?
Reinforced concrete (RC) (also called
reinforced cement concrete or RCC) is a
composite material in which concrete's
relatively low tensile strength and ductility
are counteracted by the inclusion of
reinforcement having higher tensile
strength or ductility.
Reinforced concrete, Concrete in which
steel is embedded in such a manner that
the two materials act together in resisting
forces. The reinforcing steel—rods, bars,
or mesh absorbs the tensile, shear, and
sometimes the compressive stresses in a
concrete structure.
Reinforced Concrete

Prestressed Concrete
Prestressed concrete is a structural material
that allows for predetermined, engineering
stresses to be placed in members to
counteract the stresses that occur when they
are subject to loading. It combines the high
strength compressive properties of concrete
with the high tensile strength of steel.
Prestressing is the introduction of a
compressive force to the concrete to
counteract the stresses that will result
from an applied load. ... This is done by
placing of high tensile steel tendons in a
desired profile in which the concrete is to
be cast.
 What is a Prestressed Concrete?

Construction(Reinforced Concrete)
 Mild Steel bars are placed according to the design.
 No wires cables and tendons are needed in RCC.
 Formwork have to be done with a good supervision.
 Concrete is mixed with essential ratio.
 Place the mixed aggregates in the reinforcement.
 concrete should be compacted.
Curing for 28 days.

Construction(Prestressed Concrete)
 In slab-on-ground construction, unbonded tendons are typically
prefabricated at a plant and delivered to the construction site, ready
to install.
 The tendons are laid out in the forms in accordance with installation
drawings that .
 After the concrete is placed and has reached its required strength,
usually between 3000 and 3500 psi (“pounds per square inch”), the
tendons are stressed and anchored.
The tendons, like rubber bands, want to return to their original length
but are prevented from doing so by the anchorages.
 The fact the tendons are kept in a permanently stressed (elongated)
state causes a compressive force to act on the concrete.
 The compression that results from the post-tensioning counteracts
the tensile forces created by subsequent applied loading (cars, people,
the weight of the beam itself when the shoring is removed).
This significantly increases the load-carrying capacity of the concrete.
Since post-tensioned concrete is cast in place at the job site, there is
almost no limit to the shapes that can be formed. Limitations of
Prestressing The limitations of prestressed concrete are few and really
depend only upon the imagination of the designer and the terms of his
brief. The only real limitation where prestressing is a possible solution
may be the cost of providing moulds for runs of limited quantity of
small numbers of non-standard units.

ADVANTAGE of REINFORCED CONCRETE
 Reinforced concrete has a high compressive strength compared to other
building materials.
 Due to the provided reinforcement, reinforced concrete can also
withstand a good amount of tensile stress.
 Fire and weather resistance of reinforced concrete is fair.
 The reinforced concrete building system is more durable than any other
building system.
 Reinforced concrete, as a fluid material, in the beginning, can be
economically molded into a nearly limitless range of shapes.
 The maintenance cost of reinforced concrete is very low.
 In structures like footings, dams, piers etc. reinforced concrete is the
most economical construction material.
 It acts like a rigid member with minimum deflection.
 As reinforced concrete can be molded to any shape required, it is widely
used in precast structural components. It yields rigid members with
minimum apparent deflection.
 Compared to the use of prestressed concrete in structure, reinforced
concrete requires less skilled labor for the erection of the structure.

ADVANTAGE of PRESTRESSED CONCRETE
Prestressed concrete sections are thinner and lighter than RCC
sections, since high strength concrete and steel are used prestressed
concrete.
In prestressed concrete, whole concrete area is effective in resisting
loads, unlike RCC where concrete below the neutral axis is neglected.
Thinner sections in prestressed concrete results in less self weight
and hence overall economy.
Long span bridges and flyovers are made of prestressed concrete
because of lesser self weight and thinner section. So, prestressed
concrete is used for heavily loaded structures.
Prestressed concrete members show less deflection.
Since the concrete does not crack in prestressesd concrete, rusting of
steel is minimized.
Prestressed concrete is used in the structures where tension develops
or the structure is subjected to vibrations, impact and shock like
girders, bridges, railway sleepers, electric poles, gravity dams, etc.
Precast members like electric poles and railway sleepers are produced
in factories using simple pre-stressing methods.

DISADVANTAGE of REINFORCED
CONCRETE
1.The tensile strength of reinforced concrete is about one-tenth of its
compressive strength.
2.The main steps of using reinforced concrete are mixing, casting, and
curing. All of this affects the final strength.
3.The cost of the forms used for casting RC is relatively higher.
4.For multi-storied building the RCC column section for is larger than
steel section as the compressive strength is lower in the case of RCC.
5.Shrinkage causes crack development and strength loss.

DISADVANTAGE of PRESTRESSED
CONCRETE
 Prestressed concrete construction requires very good quality control and
supervisions
 Cost of materials used in prestressed is very high (high tensile steel is about three
times costlier than mild steel).
 Prestressed concrete requires specialized tensioning equipment and devices
which are very costly.
 Prestressed concrete sections are more brittle because of use of high tension
steel.

 In RCC beam the concrete in the compression side of the neutral side of the axis alone is
effective. The concrete in the tension side of the neutral axis is ineffective. But in the
prestressed concrete beam, the entire section is effective.
 Reinforced concrete beams are generally heavy. They always need shear reinforcements
besides the longitudinal reinforcement for flexure. Prestressed concrete beams are lighter. By
providing the curved tendons and the pre-compression, a considerable part of the shear is
resisted.
 In reinforced concrete beams, high strength concrete is not needed. But in prestressed
concrete beams, high strength concrete and high strength steel are necessary. High strength
concrete is needed to resist high stresses at the anchorages. High strength steel is needed to
transfer large prestressing force.
 Reinforced concrete beams being massive and heavy are more suitable in situations where
the weight is more desired than strength. Prestressed concrete beams are very suitable for
heavy loads and longer spans. They are slender and artistic treatments can be easily provided.
Cracks do not occur under working loads. Even if a minute crack occurs when overloaded,
such crack gets closed when the overload is removed. The deflections of the prestressed
concrete beams are small.
 In reinforced concrete beams, there is no way testing the steel and the concrete. In
prestressed concrete beams, testing of steel and concrete can be made while prestressing.
The Summary of comparisons between the RCC
and prestressed concrete

Reference:
1.
2.
3.
4.
5.
Design of Prestressed Concrete Sturctures.
Written by T.Y. LIN
NED H. BURNS
Prestressed Concrete Lecture
By Uzzwal Kumar Deb Nath

Comparison of reinforced concrete and prestressed concrete

Comparison of reinforced concrete and prestressed concrete

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Comparison of reinforced concrete and prestressed concrete

Similar to Comparison of reinforced concrete and prestressed concrete (20)

Recently uploaded

Recently uploaded (20)

Comparison of reinforced concrete and prestressed concrete