Steel vs GFRP Reinforcement in Concrete Beams

This assignment explores the comparison between steel and Glass Fiber Reinforced Polymer (GFRP) as reinforcing materials for concrete beams. It examines the attributes of each material, including their strengths, weaknesses, impact on beam properties, and environmental considerations. The text also delves into the shortcomings of steel reinforcement like corrosion and spalling, contrasting them with GFRP's lighter weight and higher stiffness but lower tensile strength. Future research directions are suggested to further investigate the combined use of these materials and their performance under different loading conditions.

Steel and GFRP Reinforcement in Concrete Beams 1
COMPARISON OF CONCRETE BEAMS REINFORCED WITH STEEL AND GLASS
FIBRE-REINFORCED POLYMER (GFRP)
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Steel and GFRP Reinforcement in Concrete Beams 2
Table of Contents
1. Introduction.......................................................................................................................................3
2. Literature Review..............................................................................................................................3
3. Steel and GFRP Reinforcements......................................................................................................5
3.1. Background................................................................................................................................5
3.2. Desired properties of concrete reinforcing materials..............................................................6
3.3. Attributes of GFRP as a Concrete Beam Reinforcing Material.............................................6
3.4. Drawbacks of GFRP..................................................................................................................8
3.5. Attributes of Steel as a Concrete Beam Reinforcing Material...............................................8
3.6. Shortcomings of steel reinforcement........................................................................................9
4. Recommended Future Research.......................................................................................................9
5. Conclusion........................................................................................................................................10
References................................................................................................................................................11

Steel and GFRP Reinforcement in Concrete Beams 3
1. Introduction
Concrete is the commonest material in the construction industry and is characterized by high
compressive strength, durability and stiffness. However, plain concrete is weak in tension
because of low tensile strength and is brittle due to low fracture straini. The concrete is usually
reinforced so as to overcome these limitations. Reinforcement plays a major role in improving
structural stability and soundness of buildings. This is because concrete has good compressive
strength and poor tensile strength hence reinforcement increases the concrete’s tensile strength.
Therefore reinforced concrete has the capacity to adequately resist both compressive and tensile
stresses, which helps in preventing unacceptable structural failure. This report presents the
comparison between concrete beams that are reinforced with steel and glass fibre-reinforced
polymer (GFRP). The report contains the following sections: literature review, advantages and
disadvantages of steel reinforced concrete beams and GFRP reinforced concrete beams, future
research recommendations, conclusion, etc. The findings of this report can be used to make a
decision on whether to reinforce concrete beams using steel reinforcement or GFRP
reinforcement, depending on the construction project requirements, goals, objectives and
constraints.
2. Literature Review
Beams are structural elements that are subjected to bending only. As a result of this, one
section of the beam (top or bottom) is subjected to compression while the other section is
subjected to tension, depending on where the load is applied. Therefore the compression section
of the beam must be designed such that it resists crushing and buckling, whereas the tension
section must be designed to resist tension adequately. Reinforced concrete beams are able to
resist both compressive and tensile forces. The concrete (which has high compressive strength)

Steel and GFRP Reinforcement in Concrete Beams 4
resists compressive stresses and strain while the reinforcement (which has high tensile strength)
resists tensile stresses and strain. Therefore reinforced concrete is a composite material
comprising of concrete and reinforcing material. The main benefits of reinforced concrete are:
high compressive strength, ability to withstand high tensile stress, rational weather and fire
resistance, durability, flexibility, economical, low maintenance costs, minimal deflection, and
less skilled labor requirements. Some of the drawbacks of reinforced concrete are: low tensile
strength in comparison with compressive strength, its final quality is affected by production and
casting processes, higher cost of forms needed to cast the concrete, and can loss strength when
cracks starts developing due to shrinkage.
Steel has been used as a reinforcing material for concrete beams over a very long period of
time. In steel reinforced concrete, steel bars (also known as rebars) made from twisted filaments
with folds are anchored firmly in concrete with no risk of sliding. When the concrete cures, it
hardens with the steel rebars forming a strong composite material. One of the reasons why steel
is widely used as a concrete reinforcing material is because its rate of expansion in heat and
contraction in cold (thermal expansion coefficient) is almost the same as that of concreteii. This
prevents concrete from cracking when it is hardening or subjected to expansion and contraction
due to fluctuating environmental conditions. The steel has also been proven to be effective in
making high-strength concreteiii. Besides the traditional steel bars, steel fibresiv are also used
nowadays as concrete reinforcing materialsv. The steel fibres have a wide range of structural
applications in construction industryvi. Steel fibre reinforced concrete beams have been found to
support higher ultimate load and they remain stable even after reaching their yield stiffnessvii.
Use of GFRP as a rehabilitating or reinforcing material for structural components of
buildings began few decades backviii. This material has several advantages over the traditional

Steel and GFRP Reinforcement in Concrete Beams 5
steel rebars but other factors such as high cost have hindered its widespread application in
construction industry. GFRP are available in different forms, including: woven fabric, cranette,
hewn strand mats, ropes, wool, etc. Some of them contain epoxy resin coatings to provide
protection against cement’s alkali attack. The GFRP performs the same function as the steel
rebars – increasing tensile strength of the reinforced concreteix. Since both steel rebars and GFRP
performs the same function in reinforced concrete beams, it is vital to investigate the comparison
between these concrete reinforcing materials.
3. Steel and GFRP Reinforcements
3.1. Background
Use of steel and other metals as concrete reinforcing materials can be traced back to the 15th
century. In 1800s, many French and German engineers promoted use of reinforced concrete and
came up with several innovations such as twisting the steel rebars so as to improve their bonding
with concrete. It was until 1910 when the first steel reinforcing bar specifications were issued.
Since then, a lot of developments have followed in relation to use of steel rebars. On the other
hand, glass fibre reinforced polymer (GFRP) was first discovered in mid 1930s and has since
become a reliable reinforcing material for a wide range of civil engineering projectsx. Use of
GFRP as a reinforcement material was first discovered in Russia in 1975 where the material was
used for reinforcing a timber bridge. In 1980s, several researchers, scientists and engineers
carried out studies to establish the feasibility of GFRP replacing steel in strengthening and
repairing bridges. In 1990s, GFRP was widely used in Japan for construction of train support
structures. In 1996, design guidelines for use of GFRP in reinforced concrete were introduced by
the Japanese. Since then, GFRP has become an alternative reinforcing material to steel. The
material is now being used across the world to reinforce concrete, timber, steel and masonry

Steel and GFRP Reinforcement in Concrete Beams 6
structuresxi. The wide application of GFRP in construction industry is largely because of its
benefits over steel reinforcement. Today, many buildings across the world are constructed using
reinforced concrete, which makes them stronger and able to endure different weather and time
ravages.
3.2. Desired properties of concrete reinforcing materials
The properties of a good concrete reinforcing material are: high resistance to tensile stress
and strain, greater relative strength, good bond or compatibility with concrete, durability, thermal
compatibility, resistance to chemical and weather attack, fire resistance, cost effective,
sustainability and environmental friendliness. Steel and GFRP reinforcing materials have unique
properties, which make them suitable for different construction applications.
3.3. Attributes of GFRP as a Concrete Beam Reinforcing Material
GFRP reinforcing materials presents versatile design options because of their exceptional
fabrication flexibility, structural efficiency, high durability and low costs of production and
erection. GFRP is a type of plastic composite comprising of glass fibres that mechanically
enhance stiffness and strength of plasticsxii. The fibre gets additional protection from the resin as
a result of bonding between these materialsxiii. Some of the fundamental attributes of GFRP that
make it a suitable reinforcing material for concrete beams are as follows:
High strength: GFRP is about three times stronger than steel for an equal amount of
weight. Strength to weight ratio of the former is very high, which makes it a suitable material for
reinforcing concrete beams.

Steel and GFRP Reinforcement in Concrete Beams 7
Lightweight: GFRP weighs much less than steel reinforcement. This helps in reducing its
shipping costs, enabling easier and faster installation, and reducing the need for structural
framing.
Resistance to external damages: GFRP resists a wide range of environmental conditions,
including chemicals, salt water, acid rain, corrosion, etc. This makes it suitable for projects in
almost any environment, both indoors and outdoors.
Versatility: GFRP can be molded in virtually any form or shape, including very complex
shapes. This makes it suitable for making any form of concrete beam.
Low maintenance: GFRP does not lose its physical or mechanical properties for a very
long time – up to 30 years. If used as intended, the structure made from GFRP can last for
decades with very minimal or no maintenance needs.
Durability: GFRP is very strong and structures built from it can withstand different
expected and unexpected loadings, such as hurricanes, earthquakes, etc.
Insulation: GFRP has good heat resistance and high electrical insulation. This helps in
protecting buildings or other structures against excessive heat.
Cracking: GFRP prevents concrete beams from cracking caused by thermal or
mechanical stress that may accumulate over time.
Fatigue: GFRP has greater resistance to fatigue making it a suitable reinforcing material
to protect concrete beams against fatigue failure mode.
Radio signals: GFRP does not cause interference to the radio signals, like it is the case for
steel rebars.

Steel and GFRP Reinforcement in Concrete Beams 8
3.4. Drawbacks of GFRP
Low elastic modulus: the elastic modulus of GFRP is almost a fifth that of steel. This
reduces the capability of GFRP to withstand varied loadings.
Low flexural and tensile strength: this affects the ability of GFRP to resist loads even if
their dimensions are increased.
Creep: the creep property of GFRP changes the beams endurance performance that
affects the reliability of the beam in the long runxiv.
High cost: the cost of GFRP is relatively high compared with that of steel. This is one of
the major factors that have significantly contributed to slow adoption of GFRP as a reinforcing
material for concrete beams.
3.5. Attributes of Steel as a Concrete Beam Reinforcing Material
Some of the attributes of steel reinforcement include:
High ductility and tensile strength: steel is more ductile and has high tensile strength that
makes it able to bear greater loads. The high ductility and tensile strength of steel also increases
the overall strength of reinforced concrete beamsxv.
Cheaper: steel is abundantly available in many parts of the world and this has continued
to reduce its cost.
Reduced cracking: steel resists cracking strongly in different ways. One of these ways is
through the strong bonding between steel reinforcement and concrete. This bonding reduces
cracking of concrete when it is hardening.

Steel and GFRP Reinforcement in Concrete Beams 9
Low maintenance cost: steel has low maintenance needs, which translates into low
maintenance costs. The fact that the steel is engraved inside the concrete makes it less vulnerable
to deterioration and damages.
Durability: the high flexural strength, impact resistance, fatigue resistance and high
abrasion of steel creates durable concrete beams.
Impact and fatigue resistance: this is another great property of steel reinforcement that
makes it undergo minimal deflection (if any) and attain very high yield strength.
3.6. Shortcomings of steel reinforcement
Strength deterioration: strength of steel reinf0rced concrete decreases significantly when
the beam is exposed to extreme temperaturesxvi.
Corrosion: alkalinity of cement causes corrosion of steel reinforcement. If this happens,
the structural soundness of the entire beam declines.
Spalling: steel can also react aggressively with some aggregates in the concrete causing
spalling of the beam. This has costly effects on the structural member.
4. Recommended Future Research
In the future, there is need to conduct studies that will establish the impacts of amount of
reinforcing material used on the strength, stability and durability of reinforced concrete beams.
More studies should also be carried out to determine the impacts of steel and GFRP reinforcing
materials on the environment and the effect of type of loading on the performance of steel
reinforced or GFRP reinforced concrete beamsxvii. Researchers should also focus on establishing
the qualitative and quantitative differences between steel reinforced and GFRP reinforced
concrete beams. Last but not least, researchers should establish the feasibility of combining steel

Steel and GFRP Reinforcement in Concrete Beams 10
and GFRP reinforcing materials and if this can improve the properties and performance of
reinforced concrete beamsxviii.
5. Conclusion
Reinforcement plays a key role in preventing development of cracks in concrete beams.
These cracks form when concrete shrinks as it hardens. Plain concrete has low modulus of
rupture, is brittle in nature and its capacity to resist strain is low. As a result of this, plain
concrete has high compressive strength and low tensile strength. In order to improve flexural
strength of concrete beams and make them able to resist both compressive and tensile stresses,
reinforcement is usually added to the plain concrete. Steel and GFRP are some of the materials
that are used to reinforce concrete beams. These materials have different attributes and therefore
their effects on mechanical and physical properties of concrete beams also differ. It is important
to carry out an experimental study to determine the effect that steel and GFRP reinforcements
have on concrete beams. This comparison will help in selecting the most suitable reinforcement
between the two for a concrete beam depending on the project requirements and constraints.

Steel and GFRP Reinforcement in Concrete Beams 11
References

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