Chapter 2 Literature Review

2.0 General

In order to understand the role of steel fibers on strength and torsional

behaviour of SCC and moreover to distinguish the effect of recycled concrete
aggregates on strength properties of SCC and vibrated concrete (VC), a thorough
literature review is planned in the present chapter. The need for making the concrete
ductile through use of steel fibers for high strength SCC have been discussed.
Similarly to acquire an in-depth awareness of various software package available on
the modelling of fibrous concrete and to analyse the behaviour of steel fibrous SCC a
detailed literature is intended in the present chapter.

2.1 Review of literature on Self Compacting Concrete.

The necessity of SCC was proposed by Okamura in 1986 (Okamura et al.,

2003). For the members with congested reinforcements, this concept was used as
tool to improve the long-term durability but later due to the excellent user-friendly
characteristics of SCC the applications have spread slowly to conventional
construction industry also. SCC has a vital role to play with substantial benefits in
construction both qualitatively and quantitatively. Compared to vibrated concrete
(VC), SCC can be considered as an altered approach in mix proportioning and a new
type of high-performance material possessing good rheological characteristics. It can
be considered as an innovative approach to casting concrete obtained by adjusting
fresh concrete properties.
Ozawa et al., (1989) completed the first prototype of SCC using materials
readily available in market. By using various types of superplasticizers, a concrete
with good workability was developed. It was suitable for quick placement and had
very less permeability. V-funnel test was developed to measure the viscosity of
concrete. The influence of mineral admixtures, on the segregation resistance and
flow ability of self-compacting concrete was also investigated. It was found that the
flow ability of the concrete improved remarkably with partial replacement of Portland
cement with fly ash (10-20 %) and blast furnace slag (25-45 %) showed the required
flowing ability and strength characteristics. Self compactability was achieved easily
by altering water to cement ratio and dosage of superplasticizer by fixing coarse and
fine aggregate content to 50 % and 40 % of the solid and mortar volume

17
respectively. A summary of articles and research investigations found in the literature
on mix design methods are presented in the subsequent paragraphs.

Kuroiwa (1993) has developed a special concrete using the similar materials that
were used in conventional concrete. The proposed new concrete can easily flow to
every corner of form work and also completely fill the dense reinforcement without
any external effort. Chemical admixtures were used in order to enchase the viscosity
of that new concrete. From the laboratory test it was concluded that the proposed
concrete has excellent workability in fresh state and good durability in hardened
state.

Considering the lack of a proper mix design for SCC, Su et al., (2001)
proposed a simple mix design method for SCC, where a term Packing Factor was
introduced to calculate the quantities of aggregates. The method involved
determining the aggregate Packing Factor (PF) and influence on the strength,
flowability and self-compatibility ability. The ratio of mass of fully compacted
aggregates to mass of loosely compacted aggregates defines the Packing Factor.
Higher the packing factor, lesser is the requirement of powder content and vice
versa. Initially, the amount of aggregates required were calculated and later to fill the
voids of aggregates the paste of binders is determined. Thus, the mix proportion
obtained is tested for required flowability, self-compacting ability and other desired
SCC properties. The major factors influencing the properties of SCC were, amount of
aggregates and binders, quantity of water, as well as dosage and type of
superplasticizer (SP).

EFNARC Specifications (2005), have given guidelines for SCC, material

requirements, its composition and applications. EFNARC guidelines provides the
detailed test procedures to check the workability of SCC. The different developed
tests are Slump flow, V-funnel, J-ring, U-box and L-Box test to check the passing
ability, flowability, filling ability and segregation resistance and certain acceptance
criteria for these tests are also given in detail in the specifications.

Domone (2006), reviewed 68 case studies performed on SCC regarding the

distribution of the constituents and the corresponding workability. It was found that
the constituents and the mix proportions were spread in a relatively wide range. This
indicates that a well working SCC can be produced in many different ways with

18
various proportions between the constituents and that no unique standard rule
exists. SCC comprising a wide range of mixes were investigated and it was
concluded that there is a potential for optimizing SCC with higher efficiency, which
can be obtained based on the type of application and properties based on locally
available materials are taken into consideration.
Yazicioglu et al., (2006), examined different types of curing conditions on the
engineering properties of SCC. The authors considered three curing conditions i.e.
water curing, sealed curing and air curing. The properties of SCC obtained under
these curing conditions were compared with vibrated concrete. It was concluded
from the study that SCC containing silica fume gave higher compressive and tensile
strength values than SCC containing fly ash. For similar compressive strengths of
normal vibrated concrete and SCC, the tensile strength was higher in case of SCC. It
was also observed from the engineering properties of SCC that SCC required proper
curing in the initial days as the water-binder ratio is minimum (0.38).

Rao, et al., (2010), has developed standard and high strength SCC with different
sizes of aggregates based on NanSu mix deign. The results has shown that SCC
can be developed with different sizes of aggregates. The mechanical properties were
evaluated at the age of 3, 7 and 28 days. From the experiential results it was found
that 16 mm size and 52 % fly ash is optimal for standard strength SCC and 10 mm
and 31 % fly ash is optimal for high strength SCC.

Radhika et al., (2012), developed a mix design methodology for SCC based on
compressive packing model (CPM). It was noted that the CPM based optimization of
aggregates considers important parameters like wall effect, loosening effect and
perturbed volume that are important in deciding the aggregate portion of SCC. Three
grades of SCC mixes without and with steel fiber, were developed using CPM
concept and the method proved to be best suited for polydisperse mixtures and SCC
applicable without and with fibers. The strength and durability properties of these
mixtures were investigated and were found to be satisfactory.

Das (2012), compared the hardened properties of fly ash based Self Compacting
Concrete (SCC) with normally compacting concrete (NCC) under different curing
conditions. The curing conditions adopted were water curing, accelerated curing and
followed by water curing. The test programme included determination of
compressive strength, split tensile strength, modulus of rupture, stress-strain

19
characteristics and Poisson’s ratio of SCC and NCC subjected to different curing
conditions. The correlations developed for SCC indicated a difference in the pattern
of strength development and stress-strain behaviour compared to NCC. The
presence of fly ash particles in SCC lowered the porosity at later ages due to
pozzolanic action and improved mechanical properties as well as stress-strain
relationships. It was also concluded that curing condition significantly affects the
properties of concrete.

Rao, et al., (2013) their investigation includes developing a new mix design
methodology for SCC by modifying the Nansu method of mix design. From the
strength and workability studies carried on SCC it was noticed that there is
significant change in mix proportions with respect to packing factor, size of
aggregates, fine aggregates to total aggregate ratio, cement content, flyash and
water content on SCC. A simplified and direct mix deign method was proposed by
modifying the Nansu method of mix deign for any grade of SCC.

2.2 Review of literature on Recycled Aggregate Concrete:

The usage of recycled aggregates in concrete constructions has being carried out
from past few decades. A good amount of research work has been done on the use
of Construction Demolished Waste (CDW) as recycled aggregates by way of
replacement of natural aggregates in concrete by many researchers. Some relevant
literature on use of recycled aggregates in normal and self compacting concrete is
presented in the subsequent paragraphs.

Gumaste et al., (1998), investigated the use of recycled aggregates as replacement

for natural aggregates in concrete. The authors studied the effect of recycled
aggregates on strength properties by replacing the normal aggregates with recycled
concrete aggregate by 10 %, 20 % and 30 % by weight. The study concluded that
the compressive strength of recycled aggregate concrete was relatively less and
they opined that the variation of strength mainly depends on the strength of parent
concrete from which the aggregates are obtained.

Limbachiya et al., (2000), determined the difference between physical and

mechanical properties of natural aggregate and recycled aggregates. It was found
that recycled aggregates possess 7 to 9 % lower relative density and double water
absorption when compared to normal aggregate. It was also found from their

20
experimental results that there was no effect on strength properties up to a
replacement of 30 % of normal aggregates with recycled aggregates. They have also
proven by widespread experimental results that by using recycled aggregates higher
strength concretes can also be developed.

Rathish et al., (2001) in their research investigation, they have used construction
demolished waste as partial replacement of coarse aggregates. They have also used
mineral admixtures such as fly ash and silica fume as partial replacement of cement
to increase the workability of fresh concrete. From their studies it was established
that recycled concrete aggregate is effective materials and that can be used as
replacement of coarse aggregates, also recycled aggregates are efficient and
sustainable material, so the disposal of demolished waste can be reduced. They
have also concluded that higher percentage of replacing normal aggregates with
recycled concrete aggregates can badly effect the strength of the concrete.
Therefore the replacement of normal aggregates cannot be more than 50 %. They
have also achieved high strength concrete with recycled concrete aggregates by
using silica fume as mineral admixture and superplasticizer. The optimal dosage of
silica fume that can be substitute cement was found to be 15 %.

Guptha et al., (2002), found that a replacement of 30 % natural aggregate with

recycled aggregate didn’t affect the strength of concrete. The study observed that
the increase in replacement of recycled aggregate has decreased the compressive
strength gradually, due to inferior physical and strength characteristics of RA
compared to natural aggregate. It was stated that by adjusting the water/cement ratio
for the strength of recycled aggregate concrete specimens could be improved. Use
of fly ash in recycled concrete aggregate improved the impermeability of concrete
and thus durability.

Vivian et al., (2007), in their investigations they removed the adhered motor present
on the recycled aggregates by presoaking methods. They have found that the
reason for decrease in the compressive strength of concrete made by means of
recycled aggregates was the presence of old cement mortar on the surface of the
recycled aggregates. Due to the presence of large quantities of cement mortar on
the aggregate surface it resulted in higher porosity, water absorption there by a
weaker interfacial transition zone (ITZ) between new and old cement mortars was
established which decreases the strength of the recycled aggregate concrete. From

21
the experimental results, it was found that the behaviour of recycled aggregates was
much improved as a result of presoaking before using in concrete making.

Etxeberria et al., (2007) in their research work, authors have examined the effect of
recycled aggregates on four different compressive strengths via 20 MPa, 30 MPa, 40
MPa and 60 MPa. They have replaced the normal coarse aggregates by 25 %, 50 %
and 100 % with recycled aggregates respectively. The recycled aggregates are
presoaked before mixing it with other ingredients. The experimental results have
proven that the standard compressive strength concrete (30-40 MPa) with
replacement of normal aggregates by 25 % with recycled aggregates has displayed
similar mechanical properties as that of conventional concrete. They have also found
that by completely replacing the normal coarse aggregates with recycled coarse
aggregates the compressive strength was reduced by 15-20 % compared with
control concrete with natural aggregates.

Kumar et al., (2009), conducted experiments on the strength and performance of

recycled aggregate for use in rigid pavements. Type and level of crushing and
influence of old mortar adhering to the aggregate after crushing were taken up in the
investigation. The study concluded that increase in replacement of recycled
aggregate in natural aggregate increased the fineness modulus, water absorption,
voids ratio, elongation index, angularity number, aggregate impact value, IAPST,
abrasion loss and crushing value, while, the specific gravity, bulk density and
flakiness index decreased. The increase in old mortar content decreased the
mechanical properties of concrete.

Brito et al., (2011) investigated the use of construction demolished waste (CDW) as
recycled aggregate in concrete as a replacement of normal aggregates. The study
revealed that the feasibility of usage of Recycled aggregate in concrete. They also
studied the effect of curing conditions on mechanical performance of concrete made
with recycled aggregates. They observed that the curing conditions have greatly
affects the performance of the concrete made with recycled aggregates.

Limbachiya et al., (2012) investigated the effect of replacement of normal coarse

aggregates with recycled aggregates by 0 %, 30 %, 50 % and 100 % respectively.
They have also replaced cement with mineral admixture flyash by 30 % in concrete
production process. The studies carried on the effect of replacement of recycled

22
aggregates with natural aggregates in flyash based concretes. The mechanical and
durability studies were carried out for both normal aggregate concrete and recycled
aggregate concrete with flyash as replacement of cement. The durability studies
included chloride ion penetration, sulphate attack and carbonation for both types of
concretes. The results showed that the use of higher percentage of replacement of
normal aggregates with recycled aggregates effected the durability and strength
properties. The studies also revealed that usage of fly ash as a partial replacement
of cement resulted in improving the durability of normal concretes when compared
with recycled aggregate concrete.

Prasad (2012), identified the importance of introducing recycled concrete aggregate

as a sustainable and alternative material for natural aggregate in SCC. Two grades
of concrete were considered and glass fibers were used as passive reinforcement in
SCC to improve the ductility of concrete along with active tie confinement. The
stress-strain behaviour of tie confined fiber reinforced SCC with natural and recycled
aggregates were developed. It was observed from the investigations that RCA can
be used as a potential material in Self Compacting Concrete.

Heeralal (2013), conducted experiments on the use of recycled concrete aggregate

(RCA) for rigid pavements. The flexural fatigue behaviour of RCA was investigated
without and with steel fibers. The work identified the importance of demolished
concrete as aggregates in structural and non-structural applications. From a series of
experiments, it was concluded that the flexural strength of concrete decreased
marginally compared to natural aggregate concrete however addition of optimum
dosage of steel fibers in recycled aggregate concrete improved the flexural strength
at both static and fatigue loading conditions.

Arezoumandi et al., (2015) in their study they have made reinforced concrete
beams with recycled aggregates as 100 % replacement of normal coarse
aggregates. Flexural studies conducted on recycled aggregates beams have
displayed encouraging results compared with normal aggregate beams and existing
codes can be used in designing the beams with recycled aggregates.

Silva et al., (2016) established the relationship between modulus of elasticity and
compressive strength of recycled aggregate concrete. A statistical analysis was
performed based on the collected data to understand the loss of compressive

23
strength and modulus of elasticity on quality and level of replacement of recycled
aggregates. Furthermore, a relationship between modulus of elasticity and
compressive strength was proposed in agreement with existing codes on normal
concrete. The major influencing factors effecting the modulus of elasticity are found
to be cement paste, interfacial transition zone (ITZ) and nature of aggregates.
Finally, it was concluded that the modulus of elasticity of RCA decreases with
increased content of RA. The statistical analysis performed on relationship between
modulus of elasticity and compressive strength of RCA revealed that, RCA has
exhibited a similar behaviour as compared with conventional concrete, but as the
percentage of recycled aggregate increased there was decrease in modulus of
elasticity.

There is a lot of work done in the area of SCC and using different binding materials
and plasticizers. Literature also revealed the use of recycled aggregate materials for
making SCC. All the authors identified the importance of Self Compacting Concrete,
and that to achieve self-compactability, addition of mineral and chemical admixtures
was necessitated.

2.2.1 Literature review on Recycled aggregate based SFRSCC:

Jianming et al., (1997) have investigated the effect of steel fibers on mechanical
properties of high strength and light weight concrete. This investigations aims to
study the influence of steel fibers on Modulus of Elasticity and Poisson’s ratio of
concrete along with compressive and tensile properties. The dosage of steel fibers
were varied from 0 to 2 % volume of concrete with a constant increment of 0.5 %.
Rectangular fibers of three different lengths were used in this investigation. It is
observed there is increase in compressive strength was relatively lower compared to
tensile properties of concrete with inclusion of steel fibers. It is observed rate of
increase in tensile properties was upto 9-90 % depending on dosage and aspect
ratio of steel fibers. The increase tensile properties due to interfacial bond between
fibers and concrete. It is noted that failure of steel fiber reinforced specimens were
due slow crack progress and progressive debonding of fibers. In light weight
aggregate concrete the crack appears preliminarily in light weight aggregate rather
than cement paste under the application of load. The increase in flexural toughness
in steel fiber concrete was due to availability of number of fibers forming a bridge in

24
the crack and a more tortuous crack propagation path. Poisson’s ratio tends to
decrease with increase in fiber dosage due to crack arresting property of steel fibers.

Kou et al., (2009), carried out the research work on effect of recycled aggregate on
SCC. In their study, normal coarse aggregates was completely replaced with
recycled aggregates and examined the fresh and hardened properties of SCC. The
cement content is kept constant in all the mixes and SCC mixes were prepared by
replacing normal coarse aggregates by 0 %, 25 %, 50 %, 75 % and 100 %
respectively. The water to binder ratio of two SCC mixes was fixed at 0.53 and 0.44.
The various test on workability of fresh SCC was evaluated and also the hardened
properties like compressive, split tensile and flexural strength were performed. From
the results, it reveals that SCC made with recycled aggregates performed relatively
well when compared with control SCC and conventional concrete.

Zoran et al., (2010) in their research work, using the recycled coarse aggregates
obtained from crushed concrete as replacement of natural aggregate in self-
compacting concrete. The percentage of replacement of coarse aggregate is
replaced by 50 % and 100 % with recycled coarse aggregate. The obtained results
have shown that there is only a slight difference on strength properties compared
with control concrete without any replacement. They have also proven that recycled
aggregates can be used in SCC successfully. The experimental results shows that
the density of self compacting concrete is reduced by 2.12 % and 3.40 % for
replacement of normal coarse aggregates with recycled coarse aggregates by 50 %
and 100 % respectively.

Prakash et al., (2011) studied the effect of manufactured sand as replacement of

fine aggregate (river sand). The studies included the fresh and hardened properties
of SCC made with manufactured sand (M-Sand). They have optimized the binder
and aggregate combinations using particle packing approaches. The chemical
admixtures like, superplasticizers and viscosity modifying admixture were used to
achieve the fresh properties of SCC. The test performed on fresh SCC are slump
flow, T500mm, V-funnel, J-ring and L- box test to satisfy the passing ability, flowing
ability, filling ability and segregation. The tests performed on hardened concrete
included compressive, split tensile and flexural strength. From the experimental
results, it was concluded that comparatively higher paste volume was required to
achieve fresh properties of SCC using M-Sand as compared with river sand.

25
Experimental results also showed that only low to medium (20-60 MPa) compressive
strength concrete can be achieved by using M-Sand. The results also proven that M-
Sand can be used in producing SCC.

Ponikiewski et al., (2011) studied the effect of steel fibers on SCC by using three
different types of steel fibers i.e. hooked end, crimped end and straight end. Fresh
properties such as, Slump flow, V- funnel, J-ring and L- box test were performed on
fresh concrete. It was observed that as dosage of steel fiber increased, there was
drastic decrease in the fresh properties of SCC. Also studies on evaluation of
compressive, split tensile, flexural strength on hardened concrete on standard
concrete cubes, cylinders and prisms were carried out. From the experimental
results it was found that 0.5 % dosage of steel fibers is optimal based on fresh and
hardened properties of SCC.

Kishore et al., (2012) studied the use of steel fibers with different aspect ratio to
increase the structural performance of SCC. The objective of the study is to
determine the mechanical properties of SFRSCC with different aspect ratio of steel
fibers and to perform a comparative study on the properties of SCC without and with
steel fibers and to compare the effect of different types and aspect ratio of steel
fibers on SCC. From the experimental results, it was found that all the SCC mixes
are satisfying the lower and upper limits suggested by EFNARC. It was also
observed that for same aspect ratio hookend steel fibers has shown better properties
compared to crimped and straight end steel fibers. Due to the shape of fiber, crimped
end fiber has shown better bonding with straight end fibers. Also it was proved that
by replacing cement with flyash, the durability and microstructure of SCC has
improved.

Panda et al., (2012), carried the research work on influence of recycled concrete
aggregates (RCA) obtained from demolishing old concrete on fresh and hardened
properties of SCC and the results are compared with normal vibrated concrete
containing 100 % natural coarse aggregates (NCA). The percentage replacement of
normal coarse aggregate was varied from 10 % to 40 %. The grade of concrete
considered was M25. The experimental results indicated that the mechanical
properties of SCC with usage of recycled aggregates decreased with increase in
percentage replacement of RCA with NCA. The study also suggested that the 30 %

26
replacement of natural coarse aggregates with recycled concrete aggregates
produces better results.

Olivera et al., (2013) studied the permeability properties of SCC made with recycled
coarse aggregate. The percentage replacement of normal coarse aggregate with
recycled aggregates is by 20 %, 40 % and 100 %. The studies included strength and
durability properties of SCC made with recycled aggregates. The results from the
fresh and hardened properties revealed that it was realistic to replace the normal
aggregate with recycled concrete aggregates. From the experimental results, it was
also found that the compressive strength of SCC with RCA is decreased by 3.3 %
while dynamic modulus of elasticity is reduced by 8.0 % when compared with natural
coarse self-compacting concrete. The results have also proven that the permeability
of SCC with RCA didn’t effect much when compared with SCC with natural coarse
aggregates.

Arjun et al., (2014) studied the behaviour of SCC with recycled aggregates. The
study includes that evaluating the fresh and hardened properties of SCC by
replacing normal aggregates with recycled coarse aggregates by 25-60 % with an
interval of 5 %. From the experimental results, it was concluded that with
replacement of recycled aggregates there was slight decrease in fresh properties.
The studies on hardened properties concluded that there was no effect on strength
of SCC with recycled aggregates up to a replacement of 40 % as the percentage of
coarse aggregate, replacement beyond 40 % there was reduction in compressive
strength of SCC.

Deng et al., (2016) carried out the work on replacement of recycled aggregates in
self compacting concrete by using construction demolished waste (CDW) as a
replacement of coarse aggregates in concrete making process. The percentage
replacement varied by 25 %, 50 %, 75 %, and 100 %. It was reported that the
compressive and split tensile strengths were decreased as the percentage
replacement of recycled aggregates increased. From the experimental results, it was
concluded that the usage of recycled aggregates beyond the 50-100 % replacement
there was drastically decrease in the strength properties.
Yazici et al., (2017) have investigated the effect of recycled coarse aggregate on
SCC at various replacement levels. Recycled coarse aggregate was used in water
saturated surface dry (SSD) state. Fresh and hardened properties were evaluated

27
for SCC mixes with replacement of coarse aggregate from 0-100 % with an
increment of 25 %. Impact resistance of SCC mixes was evaluated along with
mechanical properties. It was stated that with the increase of replacement of recycle
coarse aggregate there was a decrease in density of SCC mixes. But all the fresh
properties were observed to be in accordance with EFNARC specifications. It was
reported that relative strength mixes were not significantly affected by recycled
coarse aggregate. The decrease in strength was observed to be more in case of
compressive strength than compared to split tensile and flexural strength. It was
stated that fracture energy of concrete is significantly reduced by recycle coarse
aggregate upto 60 % with 100 % replacement.

2.3 Literature review on Torsional behaviour:

2.3.1 Classical Torsion Theories:

A brief review of classical theories, applicable to the homogeneous material,
has been made in following section to get a proper insight of the basic behavior of an
element under pure torsion.
First expression to relate applied torque and resulting angle of rotation was reported
by Coloumb (1794). Author reported that the ratio of applied torque and resulting
angle of rotation was directly proportional to the fourth power of the diameter of wire
and inversely proportional to its length whereas, the proportionality constant was
found to be a function of material properties.
Navier (1826) derived an expression to relate torsional moment, polar
moment of inertia, resulting shear stress and angle of rotation per unit length and the
modulus of rigidity. It was based on the following assumptions a) Material is
homogeneous and elastic b) Plain section remains plain after twisting c) Deformation
due to the applied torque is very small d) Shape of section remains unchanged after
twisting. The theoretical modulus of rigidity using Navier’s expression was found
different for the different cross sections, though the material of the specimens was
same. Hence, the Navier’s expression was found unsuitable to define the torsional
behaviour of rectangular sections.
St.Venant (1856) proposed a semi-inverse approach to solve the torsional problem
of a rectangular section. It was based on the experimental observations that a
rectangular section shows warping as well as twisting whereas a circular cross-

28
section shows only twisting under pure torsion. St.Venant pointed out that the
assumption “Plane section remains plane after twisting” was true for the circular
sections only. Therefore, the predicted torsional behaviour of a rectangular section
by the Navier’s equation was not correct. St.Venant assumed constant warping
along the length of the rectangular section. Following expressions were proposed to
calculate torsional moment,

T= 𝛽𝑒 𝑋 3 𝑌𝜃 2.1
T= 𝛼𝑒 𝑋 2 𝑌𝜏𝑚𝑎𝑥 2.2
Where αe and βe are the coefficients, departing on aspect ratio 𝑌⁄𝑋
X and Y are smaller and larger dimensions of the cross section
T is the applied torque
θ is the angle of rotation per unit length
τmax is the maximum shear stress

Prandtl (1903), found an analogy between the stress function defining torsion and
the deflection of the membrane under uniform load, stretched over the cross section.
This analogy helped in visualizing the direction of torsional shear stresses produced
in any arbitrary cross-section. Nadai (1923) extended the Prandtl’s membrane
analogy to the plastic materials. Nadai considered a sand heap over the cross-
section of element instead of a membrane.

2.3.2 Review of literature on torsional behaviour of fiber reinforced concrete:

Hsu (1988) redefined softened truss model proposed by Hsu et al., (1985) in
generalized terms. Author explained the applicability of this model to describe the
behavior of a reinforced concrete section under shear and torsion. The proposed
method was then extended to model the behaviour of reinforced concrete deep
beam, shear transfer strength of concrete, low-rise shear wall and framed wall panel
under shear load. A new algorithm was also proposed to solve the equations of
softened truss model by iterative method.
Mansur et al., (1982) tested plain SFRC specimens under torsion by varying
aspect ratio and volume fraction. Authors used plastic theory to predict the ultimate
torsional strength which was close to the results. Unaffected torsional stiffness and
increase in torsional strength, torsional toughness and ductility with the inclusion of
steel fibers was reported.

29
 Palanjan et al., (1983) proposed an equation to predict torsional strength of
SFRC elements by modifying the expression of torsional strength of plain concrete.
In this expression authors accounted the characteristics of fiber such as aspect ratio,
volume fraction and bond. The effect of bond was included in terms of pull out
characteristics of steel fibers. Authors reported that SFRC beams have significant
reserve strength after formation of first crack.
Narayan et al., (1986) calculated the torsional strength of a reinforced-SFRC
specimen by adding the resistance provided by the concrete, fibers and conventional
steel. The contribution of concrete was calculated by the skew bending theory
whereas, the contribution of fibers was derived from the space truss analogy.
Authors suggested that the contribution of conventional steel can be calculated by
any established method. The theoretical prediction of torsional strength of reinforced-
SFRC elements was in good agreement with the test results. Authors reported that
there is increase in the ultimate torque by the partial or full replacement of stirrups by
an equivalent volume fraction of fibers.
Rahal et al., (1996) proposed a non-iterative torsion model for the reinforced
as well as prestressed concrete section under pure torsion by introducing few
empirical terms in softened truss model. The softening coefficients proposed by
Vecchio et al., (1996) were used. Authors proposed an expression to calculate the
balanced steel. An equation for the effective thickness at ultimate stage was also
proposed by assuming the softening coefficient as 0.55 and perimeter of shear flow
as 90 % of outer perimeter. The test results of specimens available in the literature
and their predicted torsional strength were in good agreement. However, the
predicted value of angle of twist at ultimate differed by an average of 27 % from the
actual test results.
Ali et al., (1999) pointed out the empiricism in the formulation proposed for
the minimum torsional reinforcement content in the ACI-318-1995. Author suggested
calculation of minimum reinforcement by equating the cracking torque and steel
contribution proposed by the space truss analogy.
KoutchouKali et al., (2001) tested high strength reinforced concrete
specimens to investigate the effect of concrete strength and amount of reinforcement
on the torsional strength of section. All the specimens were torsionally under-
reinforced. Authors made a special arrangement to measure the strain across the
depth of the concrete. This was planned to verify the bending action of struts under

30
pure torsion. The specimens with low concrete strength showed large post peak
response in comparison to the specimens having high concrete strength, indicating
change in failure mode from ductile to brittle. Authors reported that the ultimate
strength of under-reinforced specimens with same amount of steel but different
concrete strength was almost same. This indicated that there was no effect of
concrete strength on the ultimate torsional strength of under-reinforced sections.
Authors observed that in pre-cracking stage, the strains across the depth were of
compressive nature. However in post cracking stage, the strain near the surface
remained compressive but its magnitude started reducing in the depth direction. The
nature of strain was then changed to the tensile at certain depth. This confirmed the
bending action assumed in the softened truss model for the concrete struts under
warping action.
Tavio et al., (2004) proposed a methodology to calculate the effective
torsional rigidity at any intermediate stage of loading. Authors used elastic modulus
of rigidity for pre-cracking stage. Sudden increase in the twist angle at the cracking
was accounted by considering the post cracking torsional rigidity proposed by Hsu
(1973). Authors modified the same equation to represent the torsional rigidity at
ultimate. The equation for the effective torsional rigidity between the cracking and
ultimate was obtained by interpolation. To draw a complete torque-twist diagram, the
cracking torque was calculated by ACI-318-02 with modification in the value of
constant. The ultimate strength was calculated by the simplified softened truss model
(Hsu, 1990). The torque-twist diagram between the ultimate and cracking load was
drawn by calculating the effective torsional rigidity at the intermediate torque values.
Authors compared with the predicted angle of twist at 60 %, 70 %, 80 % and 90 % of
the ultimate torque with the test results of 76 specimens available in the literature.
The average of ratios of experimental to the predicted values of angle of twist was
close to 1 at all load levels. However, the coefficient of variation and standard
deviation were of order 0.2.
Fang et al., (2004) compared the torsional behavior of reinforced concrete
sections having high strength concrete and normal strength concrete. Sixteen test
specimens were cast by varying the amount of reinforcement and compressive
strength of concrete. Authors showed that the ACI-318-02 and elastic theory
underestimated the cracking strength whereas the skew bending theory
overestimated its value. The ultimate torque predicted by the ‘Compression Field

31
Theory’ and ‘Softened Truss Theory’ were in good agreement with the test results
whereas ACI-318-02 overestimated in few cases. Contrary to the observation of
other researchers (Rasmussen et al., 1995, Koutchoukali et al., 2001) in many
cases, there was an increase in the ultimate torsional strength with the increase in
compressive strength of concrete although, the specimens were under-reinforced.
Authors reported that the compressive strain at given torque in HSC was less than
the NSC specimens but at the ultimate stage, the compressive strain was generally
more for the HSC specimens.

2.3.3 Research Works on Torsional Behaviour of Steel Fiber Reinforced

Concrete (SFRC):
A reinforced concrete section cracks under torsional load when the tensile
stress component of biaxial tension-compression state exceeds the tensile strength
of the plain concrete. Researchers attempted to improve the tensile strength of a
concrete by adding steel fibers. Such a concrete is known as steel fiber reinforced
concrete (SFRC). The fibers in mortar changes the cracking characteristics and
prolongs the initial elastic stage of a reinforced concrete section under torsion. The
spalling of cover was also expected to be less in the presence of fibers. There are
good number of research reports on torsional behavior of steel fiber reinforced
concrete (ACI Committee 544, 1982), (Hoff, 1987). Few important research works
on the behavior of SFRC under torsion are briefly reviewed here.
Khan et al., (1976) tested plain SFRC specimens under pure torsion. The
specimens were cast by varying the volume fraction and aspect ratio of fibers. The
ultimate torsional strength increased with the increase in volume fraction of fibers
and was reported as a function of fiber aspect ratio. The increase in toughness with
the increase in volume fraction and aspect ratio of fibers was also reported.
Narayanan et al., (1981) tested plain SFRC specimens under the combined
bending and torsion with crimped fibers. Twelve specimens were tested under pure
torsion. An expression relating the split tensile strength and cube strength was
derived from the test data. Authors proposed an equation to predict the ultimate
torsion. An increase in the ductility with the increase in volume fraction was reported.
Mansur et al., (1982) tested plain SFRC specimens under the torsion by
varying fiber aspect ratio and volume fraction. Authors used plastic theory to predict
the ultimate torsional strength which was close to the test results.

32
 Narayanan et al., (1983) proposed an equation to predict torsional strength of
plain SFRC elements by modifying the expression of torsional strength of plain
concrete. In this expression authors accounted the characteristics of fiber such as
aspect ratio, volume fraction and bond. The effect of bond was included in terms of
pull out characteristics of steel fibers.
Kareem et al., (1985, 1986) calculated the torsional strength of a reinforced-
SFRC specimen by adding the resistance provided by the concrete, fibers and
conventional steel. The contribution of concrete was calculated by the skew bending
theory whereas the contribution of fibers was derived from the space truss analogy.
Authors suggested that the contribution of conventional steel can be calculated by
any established method. The theoretical prediction of torsional strength of reinforced-
SFRC elements was in good agreement with the test results.
Mansur et al., (1989) tested few reinforced-SFRC specimens by varying the
amount of longitudinal steel, transverse steel and fibers. Authors modified the
softened truss model (Hsu, 1988) by incorporating the material properties of SFRC,
to predict the torsional strength. Authors also accounted the tensile strength of matrix
by including the constitutive relationship of SFRC in tension. An algorithm was
proposed to calculate the torque-twist response of the reinforced SFRC specimens.
The predicted and experimental ultimate torque and corresponding angle were close.
Author reported improvement in the torsional strength and change in cracking
characteristics due to the inclusion of fibers in a reinforced concrete section.
Till 1990, most of the investigations regarding SFRC under torsional actions
were related to its behavioral aspects. There were no clear-cut design stipulations for
the SFRC elements under torsional loads. Nanni (1990) proposed a design
approach based on available literature. In the first part of paper, literature available
on the torsional behavior of plain SFRC and reinforced SFRC was presented. The
behavioral response of these elements was critically reviewed by the author. In
second part, the design stipulations for rectangular reinforced-SFRC section were
proposed. It was based on the observed behavior and torsion design stipulation
proposed by ACI 318-89. The proposed design procedure was then compared with
available test results. The design solution was found upper bound.
T.D.Get al., (2002) presented a thorough investigation of reinforced- SFRC
elements under pure torsion. Plain and reinforced-SFRC elements were cast by
varying the concrete strength, cross-sectional aspect ratio and volume fraction of

33
fibers. An expression for the ultimate strength of plain- SFRC was proposed by the
author. The torsional rigidity in pre-cracking stage of reinforced-SFRC specimen was
assumed same as that of the plain-SFRC elements. The cracking torque of
reinforced-SFRC elements was assumed equal to the ultimate torsional capacity of
the plain-SFRC elements. Author used softened truss model to define the post-
cracking behavior of reinforced- SFRC elements. A design methodology was
proposed for the reinforced-SFRC elements to resist the torsional load. Author also
presented failure mode diagrams and strength contours for reinforced-SFRC section
as a design aid.
Seshu et al., (2003) studied the behavioural aspect of the steel fiber
reinforced concrete by testing twenty plain SFRC specimens under pure torsion. The
cross-sectional dimension of the specimens was kept same whereas the volume
fraction of the fibers and compressive strength of concrete were varied. Authors
reported an increase in ultimate torsional strength, torsional toughness and torsional
stiffness with increase in fiber content. A prediction equation similar to the elastic
theory was forwarded. Coefficient ‘α’ of proposed equation was calculated by an
empirical equation.
T.D.G et al., (2005) presented an analytical model for the torsional strength of
reinforced-SFRC elements under pure torsion. St. Venant’s equations were adopted
to derive the torque-twist response in the pre-cracking stage. The cracking strength
of a reinforced SFRC section was assumed to be equal to the ultimate strength of
plain-SFRC. In posting-cracking range, the behaviour was predicted by the softened
truss model. The equilibrium and compatibility equations were same as proposed by
the Hsu (1988), however, the material properties were modified to include the SFRC
characteristics. The tensile strength of SFRC was included by considered the
constitutive law. The softening coefficient proposed by Veechio et al., (1996) was
used. Authors validated the proposed model by testing fifteen reinforced-SFRC
specimens.
Chalioris et al., (2006) have studied the torsional behaviour of RC members
with behaviour model and experimental study. To predict torsional behaviour in this
investigation author had a combined approach of smeared crack analysis and
softened truss model. In experimental study, author has varied the spacing of
transverse reinforcement and height to width ratio of the beam. A good agreement
was observed between experimental results and predicted approach.

34
 Reza et al., (2009) have investigated the torsional behaviour of concrete with
carbon fiber reinforced polymer. Carbon fiber reinforced polymer (CFRP) sheet
wrappings were used in different configurations in full and strip wrappings. The
contribution of CFRP towards the strengthening of torsional behavioral of concrete is
been studied. Three different ratios of longitudinal to transverse reinforcements were
used in this investigation. The authors reported that the torsional behaviour of beams
strengthened by one ply and two plies of CFRP sheet was close to various steel
reinforcements ratios, in comparison to increase with amount of steel reinforcement.
The beams with higher amount of total torsional reinforcement had higher torsional
capacity for a given twist angle. The beams with higher amount of torsional
reinforcements failed at higher levels of ultimate torque and strain.
Eisa et al., (2014) have investigated the effect of hooked steel fiber on SCC
under combined bending and torsion. Six beams were cast and tested by varying
dosage of steel fiber and longitudinal reinforcement. Significant increase in ductility
and toughness was observed in post-cracking zone of beams with steel fibers.
Torsional capacity of high strength SCC with fibre volume fraction of 1.5 % has
increased upto 30 % in comparison to beams without steel fibers. The validation of
experimental results is done using finite element analysis in ANSYS software. The
results of FEM analysis have underestimated ultimate loads of experimentally tested
beams by 7-13 %. This closeness of results between FEM and experiments indicate
that ANSYS software can be used to predict the load carrying capacity of high
strength steel fiber reinforced SCC.
Behara et al., (2015) have studied the torsional behaviour of concrete by
providing ferrocement U-Jacketing experimentally. The parametric variation in this
investigation is the number of mesh layers with four possible cases of torsion by
varying longitudinal and transverse reinforcements. The experimental results have
shown that the effect of three mesh layers on ultimate torque was nearly equal to
four and five mesh layers. It was noted in all states of torsion U warps have provided
better torque carrying capacity. Better rotation capacity was shown by under
reinforced beams whereas, completely over-reinforced beams had effective
resistance towards torque.
Lokesh et al., (2015) have studied the torsional behaviour of recycled
aggregate concrete beams experimentally. Recycled aggregate is obtained from
demolished building waste of 35 year old. The percentage of replacement is varied

35
from 0 to 100 % with a regular increment of 25 %. The experimental results showed
that uniaxial compression strength decrease with the increase of RA dosage. It was
also noted that, coarse aggregate replacement of 50 % doesn’t affect the torsional
strength more than 10 % whereas, complete replacement of recycled aggregates
adversely affect torsional behaviour of concrete.
Abdelrazik et al., (2016) have investigated the effect of types of fibers on
mechanical and crack resistance of super workable concrete (SWC). The
enhancement of crack resistance is studied for two different fiber volumes. Hook end
steel fibers of 3D, 4D, 5D and polypropylene fibers were added in different
combinations. Mixtures with low fiber factor possessed lower flow and passing ability
than similar mixtures with higher fiber factor. Hookend 5D with 0.75 % dosage by
volume of concrete had significant performance in all nine mixes of different fiber
combinations. Significant increase is observed in toughness of SWC mixes with 5D
hookend fibers in all dosages of fiber volume.
2.4 Summary of Literature Review:

From a detailed literature review on SCC, it was evident that SCC is new type
of concrete can compact in to every corner of formwork by means of its self-weight.
There is abundant amount of literature available on SCC. Usage of recycled
aggregates in concrete as a replacement of natural aggregates is now gaining
importance especially in SCC. From the review of literature, it was found that the use
of recycled aggregates as substitute to natural aggregates is an effective way of
handling disposal of waste concrete when used at proper replacement proportions,
and also influence of steel fibers on SCC was studied. The literature available on the
torsional behaviour of steel fiber reinforced SCC is very limited. The studies on the
torsional behaviour of recycled aggregates based steel fiber reinforced SCC are very
less. The validation of torsional behaviour of fiber reinforced SCC and VC using FEM
is scant.
Based on the detailed literature review, scope and objectives are formulated along
with detailed research methodology and is presented in the chapter-3

36