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International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 01, January 2019, pp. 1147-1158, Article ID: IJCIET_10_01_106
Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=01
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
FLEXURAL BEHAVIOR OF HIGH STRENGTH
REINFORCED CONCRETE BEAMS
STRENGTHENED BY HYBRID FIBERS
Qais F. Hasan
Kirkuk Technical College, Northern Technical University, Iraq
Maan A. Al-Bayati
Civil Engineering Department, College of Engineering, Tikrit University, Iraq
Dler A. Al-Mamany
Kirkuk Technical College, Northern Technical University, Iraq
ABSTRACT
An experimental program is achieved to study the enhancement gained from adding
different volumetric ratios of hybrid steel, basalt, and glass fibers to high strength
concrete mixes, and to investigate the flexural behavior of rectangular reinforced
concrete beams produced from these fibrous mixes. Ten rectangular beams, which are
identical in geometry and reinforcement, are tested. The first one is a control beam,
group A consist of three beams strengthened by different ratios of steel fibers only,
group B consist of three beams strengthened by different ratios of hybrid steel-basalt
fibers, and group C consist of three beams strengthened by different ratios of hybrid
steel-glass fibers. Results and comparative studies expressed in the form of graphs and
tables show variable enhancement values in crack, yield, and ultimate loads capacities
for the tested beams. Standard high strength concrete cubes and cylinders test results
indicate that compressive strength for all the fibrous mixes is slightly worsened,
especially for hybrid steel-basalt fibers, due to the increase in matrix porosity whereas
the splitting tensile strength is enhanced. Generally, yield and ultimate load capacities
for most of the fibrous beams are reduced, especially for hybrid steel-basalt fibrous
beams due to the smooth texture of basalt fibers. In addition, adding glass fibers
hybridly with steel fibers enhances crack formation and propagation without a
noticeable reduction in yield and ultimate load capacities.
Key words: Hybrid fibers, High strength, Fibrous beams, Ultimate loads.
Cite this Article: Qais F. Hasan, Maan A. Al-Bayati and Dler A. Al-Mamany, Flexural
Behavior of High Strength Reinforced Concrete Beams Strengthened by Hybrid Fibers,
International Journal of Civil Engineering and Technology, 10(01), 2019, pp. 1147-
1158.
Qais F. Hasan, Maan A. Al-Bayati and Dler A. Al-Mamany
http://www.iaeme.com/IJCIET/index.asp 1148 [email protected]
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=01
1. INTRODUCTION
The concept of adding fibers to improve material properties is ancient [1], for example the
Mesopotamians used a straw to reinforce sunbaked bricks. Nowadays, fibers are produced in
many forms such as steel, glass, basalt, carbon, and others, however, steel fibers are the most
common one. Experiments using glass fibers have been conducted in the United States since
the early 1950's as well as in the United Kingdom and in Russia [2]. Enhanced spalling strength,
ductility, and toughness of concrete is found by adding 1.5 % volumetric ratio of steel fibers.
Using this percentage, different studies show that concrete compressive strength is enhanced
up to 15 % [3], 37 % [4], and 10 % [5]. Experimental results gained by [6] show that the
inclusion of basalt and glass fibers, separately, in concrete mix reduces the workability of this
mix. These studies observed that the splitting tensile strength of concrete increases up to 40 %
when adding 1.0 % basalt fibers, and no improvement in strength is observed after a dosage of
0.50 % glass fiber. Hybrid steel-polyethylene fibers are used in reinforced cementitious
composites by [7]. It is found that polyethylene fibers improve strain capacity while steel fibers
improve ultimate tensile strength. Hybrid polyvinyl-alcohol fibers are used to strengthen
mortar matrix with different types of light weight sand by [8]. It is observed that the ultimate
load capacities of the strengthened composites are almost the same irrespective of volume
fractions of light weight sand. The effect of adding hybrid steel-cellulose fibers on flexural and
direct shear capacities of concrete elements is studied by [9], while the impact of adding hybrid-
sized carbon fibers on the mechanical properties of Portland cement mortar is investigated by
[10]. Effect of adding different percentages of steel, basalt, and glass fibers separately on the
behavior of reinforced concrete beams, are presented in many researches [11-15], however, the
impact of adding hybrid fibers [16], by combining different types and volumetric ratios of these
three fibers, on high strength concrete compressive and splitting tensile strengths as well as on
beam flexural load-deflection behavior is still under discussion. In addition, lack of
experimental data available in literature for the behavior of high strength reinforced concrete
beams strengthened with different volumetric ratios of these hybrid fibers makes designers
reluctant to opt such fibers as a high strength concrete matrix additive. This study provides
designers with experimental database including tables, graphs, comparisons, and discussions
needed to support their decision in choosing the appropriate hybrid steel, basalt, and glass fibers
for high strength reinforced concrete beams strengthening.
2. RESEARCH SIGNIFICANCE
An experimental program is suggested in this study to give a database and to show and compare
the results and the enhancement gained from adding different volumetric ratios of hybrid fibers
of steel, basalt, and glass to high strength concrete mix through testing sixty standard concrete
cube for compressive strength, sixty standard concrete cylinders for splitting tensile strength,
and ten rectangular reinforced concrete beam specimens for flexural performance. Crack, yield,
and ultimate load-deflection capacities are to be denoted, compared, and discussed to illustrate
well the enhancement gained, in addition, cracks that developed and propagated at beams' faces
are to be followed and marked to show and explain the failure modes.
3. EXPERIMENTAL PROGRAM
To get high strength concrete a mix proportion of 1:1.5:2.8 for cement type (II/B-LL 32.5R),
natural river sand, and crushed stone of 10 mm maximum size, respectively, are used with
water/cement ratio of 0.48 and grade 50 super-plasticizer of 1.8 kg/m3 to produce adequate
Flexural Behavior of High Strength Reinforced Concrete Beams Strengthened by Hybrid Fibers
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workability. Hooked-end shape steel fiber (SF), chopped basalt fiber (BF) and S-type glass
fiber (GF) shown in Figure 1, with the properties given in Table 1, are used hybridly for high
strength concrete mix strengthening.
Figure 1 Fibers used (a) Basalt, (b) Glass, and (c) Steel
Table 1 Specifications of the fibers used
Fiber
type
Diameter(µ
m)
Length(m
m)
Elasticity modulus
(GPa)
Specific gravity
(kg/m3)
Tensile strength
(MPa)
Basalt 20 12 89 2800 4100
Glass 13 12 77 2600 3400
Steel 550 30 200 7850 1500
Ten reinforced rectangular high strength concrete beam specimens of the same properties
and reinforcement details shown in Figure 2 are tested, following ASTM specifications [17]
under four points loading, and compared to study the enhancement gained from adding
different normal and hybrid volumetric ratios of the three mentioned fiber types. The first one
is a control beam (CB), as shown in Table 2. Group A consists of three beams strengthened
with different volumetric ratios of steel fibers. Group B consists of three beams, also,
strengthened with different volumetric ratios of hybrid steel-basalt fibers. Group C consists of
three beams, also, strengthened with different volumetric ratios of hybrid steel-glass fibers. In
addition, the data of sixty standard 100 x 100 x 100 mm3 concrete cubes sampled, compacted,
cured, and tested following ASTM specifications [18, 19, and 20], and sixty standard 100 mm
diameter by 200 mm length concrete cylinders sampled, compacted, cured, and tested
following ASTM specifications [18, 20, and 21] (as 6 cubes and 6 cylinders for each concrete
batch), are used to get both compressive (σ) and splitting tensile (fts) strengths for normal and
fibrous concrete mixes at 28 days age. To well visualize the failure modes and crack patterns,
the tested beams are painted with white emulsion and a grid of 50 mm x 50 mm lines is made
(c)
Qais F. Hasan, Maan A. Al-Bayati and Dler A. Al-Mamany
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for each one, as shown in Figure 3. The cracks initiation is shown in alphabetic order and their
propagation is marked with multi-color pen and the total applied load is denoted at each stage
of crack propagation.
Figure 2 Geometry and reinforcement details of the tested beams
Figure 3 Sample beam under test machine
Table 2 Beams labeling and the corresponding fibers volumetric ratios
Group name Beam or batch label SF (%) BF (%) GF (%)
- CB - - -
A
SF0.5 0.5 - -
SF1.0 1.0 - -
SF1.5 1.5 - -
B
SF0.75BF0.25 0.75 0.25 -
SF0.5BF0.5 0.5 0.5 -
SF0.25BF0.75 0.25 0.75 -
C
SF0.75GF0.25 0.75 - 0.25
SF0.5GF0.5 0.5 - 0.5
SF0.25GF0.75 0.25 - 0.75
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4. RESULTS AND DISCUSSIONS
4.1. Compressive and Splitting Tensile Strengths
Summary and comparisons of compressive strength and splitting tensile strength results for
high strength normal, and fibrous concrete cubes and cylinders are shown in Table 3. These
results show that the compressive strength for all the fibrous batches (σFRC) is decreased, in
general, when compared to control batch compressive strength (σCB), and a maximum reduction
by 23% is noticed when testing concrete batch SF0.25BF0.75 in group B when the basalt
contributes with steel to make a hybrid fibrous concrete mix. These results show that adding
basalt fibers hybridly with steel fibers has a deleterious effect on concrete compressive
strength, while adding steel fibers only (group A) has no noticeable effect. Although the cause
of reduction in compressive strength is not exactly clear, but poor interface of the fibers with
cement paste as well as the increase in porosity of the matrix due to fibers addition could be
the main contributing factors, especially because the concrete is of high strength type.
Splitting tensile strength is increased by adding different fibers, especially steel fibers, as
shown in Table 3. It means that fibers addition contributes well in enhancing bond
characteristics of concrete mix. Discrimination of steel fibers in this field makes them the better
choice when splitting tensile strength is a matter of concern. Maximum gain is noticed for batch
SF1.0, with 1.0% steel fibers, by 147% when compared to CB batch. Adding basalt fibers to
hybrid beam batches of group B shows the minimum gain in splitting tensile strength among
the other strengthened batches, and this is due do the smooth texture for basalt fibers which
weakens interlock forces between concrete materials, therefore, hybrid steel-basalt fibers may
be a worse option when the splitting tensile strength is needed to be enhanced. Hybrid batch
SF0.5GF0.5 results, at group C, represent the best fiber combination to enhance both
compressive and splitting tensile strengths. It suffered a reduction only by 4 % in compressive
strength and gained an increase by 128 % in splitting tensile strength compared to control beam
batch.
Table 3 Summary of compressive and splitting tensile strengths result
Group Batch σ (MPa) σFRC/ σCB Change in σ
(%) fts(MPa)
(fts)FRC/
(fts)CB
Change in
fts (%)
- CB 63.66 1 - 2.85 1 -
A
SF0.5 61.71 0.97 - 3 6.85 2.40 140
SF1.0 62.89 0.99 - 1 7.03 2.47 147
SF1.5 62.04 0.97 - 3 6.94 2.44 143
B
SF0.75BF0.25 50.37 0.79 - 21 3.66 1.28 28
SF0.5BF0.5 52.94 0.83 - 17 3.70 1.30 30
SF0.25BF0.75 49.15 0.77 - 23 3.89 1.36 36
C
SF0.75GF0.25 58.72 0.92 - 8 5.56 1.95 95
SF0.5GF0.5 61.09 0.96 - 4 6.51 2.28 128
SF0.25GF0.75 55.42 0.87 - 13 4.42 1.55 55
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4.2. Beams Crack, Yield, and Ultimate Values
Crack load values and comparisons for all the tested beams, shown in Table 4, illustrate the
effect of adding different normal and hybrid fibers. In general, most of crack load capacities
are increased, with maximum increment by 60% for beam SF1.0 when compared to control
beam (CB), because of the enhancement done in tension zone due to fibers existence which
improves delay of crack formation and propagation through the beam depth. Adding hybrid
steel-glass fibers by different percentages in group C shows a noticeable enhancement in crack
load capacities, which means that this combination represents a good choice of hybrid fibers
when the crack load capacity is a matter of concern. On the other side, using and increasing the
percentage of the smooth texture basalt fibers in hybrid steel-basalt worsen the beam capacity
for crack loads, with a maximum reduction by 26% for beam SF0.25BF0.75. Post cracking
load behaviors shown in Figures (4-6) show different stiffness reductions for most of the
fibrous beams, and hence, reductions in their yield load capacities compared to CB. This is due
to the increase in porosity of these high strength concrete mixes, which led to reductions in
compressive strength, and hence, reductions in beams flexural strength. A valuable reduction,
by 24%, in yield load capacity is noticed for hybrid steel-basalt beam SF0.75BF0.25 at group
B, as shown in Table 4. A review of the yield load capacity reductions for beams of this group
indicates that the combination between steel and basalt fibers may be a worse choice for hybrid
fiber addition when the yield load capacity is required to be maintained. A 9% increment in
yield load capacity is noticed for beam SF1.0, which has also the maximum increment in crack
load capacity among all the fibrous beams. This fact makes the mix with 1.0% steel fiber has
the optimum gain in both crack and yield load capacities.
Table 4 Load-deflection values and comparisons for the tested beams
Group Beam Pcr
(kN)
change
in Pcr
(%)
Δcr(mm) change
in Δcr(%) Py(kN)
change
in Py(%) Δy(mm)
change in
Δy(%)
Pu
(kN)
change in
Pu (%)
- CB* 17.6 - 2.5 - 50.1 - 5.7 - 54.9 -
A
SF0.5 19.4 10 3.4 36 44.3 -12 6.5 13 50.5 -8
SF1.0 28.1 60 3.1 24 54.8 9 5.9 2 55.2 0.6
SF1.5 15.4 -13 2.5 0 50.3 0.4 6.5 13 52.6 -4
B
SF0.75BF0.25 18.9 7 4.8 92 38.1 -24 8.2 42 40.3 -27
SF0.5BF0.5 17.4 -1 2.5 0 45.7 -9 6.1 5 46.5 -15
SF0.25BF0.75 13.1 -26 2.6 4 44.5 -11 6.6 15 50.3 -8
C
SF0.75GF0.25 19.6 11 3.9 56 45.3 -10 7.4 29 48.0 -13
SF0.5GF0.5 21.9 24 3.0 20 52.4 5 6.5 14 55.8 2
SF0.25GF0.75 23.9 36 4.2 68 47.4 -5 7.2 25 50.0 -9
*Reference beam
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Figure 4 Load-deflection curves for CB and group A beams
Ultimate load capacities for all the fibrous beams are also reduced in general. The worst
reduction is by 27% for beam SF0.75BF0.25 in group B, which has also the worst reduction in
yield load capacity. These reductions are accompanied with the maximum increments in both
crack and yield deflections, which make it relatively the worst choice for maintaining yield and
ultimate load and deflection capacities. The presence of basalt fibers, which affects concrete
compressive strength and slightly enhances splitting tensile strength as mentioned earlier,
worsens flexural capacities of the related tested beams. It is obvious from load-deflection
curves that the strain energy and the ductility ratio for the fibrous beams are, to some extent,
maintained except what is noticed when testing beam SF0.75BF0.25, which has significant
reductions in these two characteristics.
In the present study, all the hybrid volumetric fiber ratios have a sum of 1.0% for each
beam, therefore, another load and deflection comparisons are made for the hybrid beams
relative to the new control beam SF1.0 with 1.0% steel fiber, as shown in Table 5. As the steel
fiber percentage is reduced and basalt fibers are replaced hybridly the crack load capacities are
reduced, with a maximum value by 53% for beam SF0.25BF0.75, while increasing glass fiber
percentage at the expense of steel fibers has a praised effect on crack load capacity reductions
with a minimum value by 15% for beam SF0.25GF0.75. Yield and ultimate load capacities are
also reduced for all the hybrid fibers beams compared to SF1.0, and the maximum reduction in
yield capacity is noticed for beam SF0.75BF0.25 by 30%. Maximum reduction in ultimate load
capacity is noticed for beam SF0.75BF0.25, also, by 27%, which means that this hybrid fiber
combination represents the worst case in yield and ultimate capacities loss. Beam SF0.5GF0.5
gives yield and ultimate load capacities close to reference beam (SF1.0), and this makes the
replacement of steel fibers by glass fibers is useless in this case.
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Table 5 Comparisons of hybrid beams relative to beam SF1.0
Beam Pcr (kN) change in
Pcr (%) Δcr(mm)
change
in Δcr
(%)
Py(kN) change
in Py (%) Δy(mm)
change
in Δy
(%)
Pu
(kN)
change in
Pu (%)
SF1.0* 28.1 - 3.1 - 54.8 - 5.9 - 55.2 -
SF0.75BF0.25 18.9 -33 4.8 55 38.1 -30 8.2 39 40.3 -27
SF0.5BF0.5 17.4 -38 2.5 -19 45.7 -16 6.1 3 46.5 -16
SF0.25BF0.75 13.1 -53 2.6 -16 44.5 -19 6.6 12 50.3 -9
SF0.75GF0.25 19.6 -39 3.9 26 45.3 -17 7.4 26 48.0 -13
SF0.5GF0.5 21.9 -22 3.0 -3 52.4 -4 6.5 12 55.8 1
SF0.25GF0.75 23.9 -15 4.2 35 47.4 -14 7.2 22 50.0 -10
*Reference beam
Figure 5 Load-deflection curves for CB and group B beams
Figure 6 Load-deflection curves for CB and group C beams
4.3. Crack Patterns and Failure Modes
Crack pattern of control beam CB, shown in Figure 7 indicates that the crack is initiated at the
tension face at beam mid-span. With load increment, other cracks are developed within the
middle third of the span and propagated successively. Crack patterns and failure modes shown
in Figures (7-10) indicate that failure of all the tested beams goes to be a flexural failure, and
this is done after yielding of main bottom reinforcement and before reaching ultimate load
which accompanied by successive compression concrete crushing. A quick review of fibrous
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beams’ crack patterns, shown in Figures (8-10), illustrates that the formation of cracks is
delayed and the propagation of these cracks are reduced, and hence, all the fibrous beams are
enhanced compared to the control beam (CB). The crack patterns shown in Figure 8 for group
A, which has different volumetric ratios of steel fibers, indicate that the first main crack which
is formed in the middle of the tested beam still propagate with a limited formation of new
cracks. This is due to the enhancement in high strength concrete bond characteristics when
hooked-end steel fibers are added. The failure mode of this group is, also, done by yielding of
tension steel reinforcement followed by concrete compression failure with delamination of
multilayers due to enhanced tensile properties of fibrous high strength concrete.
Figure 7 Crack pattern and failure mode for the control beam (CB)
Beam SF0.5
Beam SF1.0
Beam SF1.5
Figure 8 Crack patterns and failure modes for group A beams
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Beam SF0.75BF0.25
Beam SF0.5BF0.5
Beam SF0.25BF0.75
Figure 9 Crack patterns and failure modes for group B beams
Beam SF0.75GF0.25
Beam SF0.5GF0.5
Beam SF0.25GF0.75
Figure 10 Crack patterns and failure modes for group C beams
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5. CONCLUSIONS
An experimental program is followed in this study and consisted of one hundred twenty
standard high strength concrete cubes and cylinders, in addition to ten reinforced concrete
beams, to investigate the behavior and the enhancement gained from adding normal and hybrid
steel, basalt, and glass fibers. Test results indicate reductions in the compressive strength for
all the fibrous concrete mixes compared to control mix (CB) in the time that steel fibers have
no noticeable effect. Splitting tensile strengths are increased for all the fibrous concrete mixes,
especially for steel fibers mixes. Hybrid steel-glass fibers mixes show better enhancement in
splitting tensile strength compared the hybrid steel-basalt fibers mixes. Results of load-
deflection curves indicate that most of crack load capacities of fibrous beams are increased,
especially when adding steel fibers only, which means better characteristics in cracks formation
and propagation for the fibrous beams, and the case is also when replacing a percentage of steel
fibers with glass fibers without a noticeable reduction in yield and ultimate load capacities.
These capacities are slightly worsened when a percentage of steel fibers is replaced by basalt
fibers because of the basalt's smooth texture which weakens concrete interlock forces
especially the concrete is of high strength type which is susceptible to any deficiency in its
interlock. To some extent, strain energy and ductility ratio for the fibrous beams are maintained.
Additional comparisons of the hybrid fibrous beams with 1.0% steel fibers beam show that
crack load capacities for hybrid steel-basalt fibers beams are reduced when adding relatively
high basalt percentages more than what noticed for hybrid steel-glass fibers beams, and this is
due to smooth texture for basalt fibers. Crack patterns and failure modes of all the tested beams
assure that the failure is of flexural type, by yielding of tension steel reinforcement followed
by concrete compression failure. In addition, cracks formation and propagation are enhanced
for all the fibrous beams. The enhancement in some fibrous mixes are extended to the
compression zone, which is clear when adding hooked-end steel fibers only. Extending the
present study to include more types of hybrid fibers, different beams cross sections, deep
beams, and time-dependent effects, are suggested as future works.
REFERENCES
[1] Rashiddadash, P., Ramezanianpour, A. and Mahdikhani, M. Experimental investigation on
flexural toughness of hybrid fiber reinforced concrete (HFRC) containing metakaolin and
pumice. Journal of Construction and Building Materials, 51(1), 2014, pp. 313-320.
[2] Ashour, S., Mahmood, K. and Wafa, F. Influence of steel fibers and compression
reinforcement on deflection of high-strength concrete beams. ACI Structural Journal, 94(6),
1997, pp. 611-624.
[3] Johnston, C. Steel fiber reinforced mortar and concrete: a review of mechanical properties.
ACI Special Publication, SP-44, 1974, pp. 127-142.
[4] Khaloo, A. and Kim, N. Mechanical properties of normal to high-strength steel fiber-
reinforced concrete. Journal of Cement, Concrete and Aggregates, 18(2), 1996, pp. 92-97.
[5] Thomas, J. and Ramaswamy, A. Mechanical properties of steel fiber-reinforced concrete.
Journal of Materials in Civil Engineering, 19(5), 2007, pp. 385-392.
[6] Kizilkanat, A., Kabay, N., Akyüncü, V., Chowdhury, S. and Akça, A. Mechanical
properties and fracture behavior of basalt and glass fiber reinforced concrete: An
experimental study. Journal of Construction and Building Materials, 100(C), 2015, pp. 218-
224.
[7] Ahmed, S. and Maalej, M. Tensile strain hardening behaviour of hybrid steel-polyethylene
fiber reinforced cementitious composites. Journal of Construction and Building Materials,
23(1), 2009, pp. 96-106.
Qais F. Hasan, Maan A. Al-Bayati and Dler A. Al-Mamany
http://www.iaeme.com/IJCIET/index.asp 1158 [email protected]
[8] Ahmed, S. and Mihashi, H. Strain hardening behavior of lightweight hybrid polyvinyl
alcohol (PVA) fiber reinforced cement composites. Journal of Materials and Structures,
44(6), 2011, pp. 1179-1191.
[9] Banthia, N., Majdzadeh, F., WU, J. and Bindiganavile, V. Fiber synergy in hybrid fiber
reinforced concrete (HyFRC) in flexure and direct shear. Journal of Cement and Concrete
Composites, 48, 2014, pp. 91-97.
[10] Shu, X., Graham, R., Huang, B. and Burdette, E. Hybrid effects of carbon fibers on
mechanical properties of Portland cement mortar. Journal of Materials and Design, 65(C),
2015, pp. 1222-1228.
[11] Krassowska, J. and Lapko, A. The Influence of steel and basalt fibers on the shear and
flexural capacity of reinforced concrete beams. Journal of Civil Engineering and
Architecture, 7(7), 2013, pp. 789-795.
[12] Patil, R. and Kulkarni, D. Comparative study of effect of basalt, glass and Steel fiber on
compressive and flexural strength of concrete. International Journal of Research in
Engineering and Technology, 3(1), 2014, pp. 436-438.
[13] Sahoo, D. and Sharma, A. Effect of steel fiber content on behavior of concrete beams with
and without stirrups. ACI Structural Journal, 111(5), 2014, pp. 1157-1166.
[14] Biolzi, L. and Cattaneo, S. Response of steel fiber reinforced high strength concrete beams:
Experiments and code predictions. Journal of Cement and Concrete Composites, 77, 2017,
pp. 1-13.
[15] Lee, J., Cho, B. and Choi, E. Flexural capacity of fiber reinforced concrete with a
consideration of concrete strength and fiber content. Journal of Construction and Building
Materials, 138, 2017, pp. 222-231.
[16] Banthia, N. and Gupta, R. Hybrid fiber reinforced concrete (HYFRC): fibers energy in high
strength matrices. Journal of Materials and Structures, 37, 2004, pp. 707-716.
[17] ASTM C1609/C1609M. Standard test method for flexural performance of fiber-reinforced
concrete (using beam with third-point loading). West Conshohocken, PA, ASTM
International, 2007.
[18] ASTM C172. Standard practice for sampling freshly mixed concrete. West Conshohocken,
PA, ASTM International, 2007.
[19] ASTM. C39/C39M. Standard test method for compressive strength of cylindrical concrete
specimens. West Conshohocken, PA, ASTM International, 2003.
[20] ASTM. C31/C31M. Standard practice for making and curing concrete test specimens in the
field. West Conshohocken, PA, ASTM International, 2003.
[21] ASTM. C496. Standard test method for splitting tensile strength of cylindrical concrete
specimens. West Conshohocken, PA, ASTM International, 2007.