Mechanical Properties of Steam Cured High-Strength Steel Fiber-Reinforced Concrete with High-Volume Blast Furnace Slag
International Journal of Concrete Structures and Materials
Mechanical Properties of Steam Cured High-Strength Steel Fiber-Reinforced Concrete with High-Volume Blast Furnace Slag
In this study, the effects of water-to-binder (W/B) ratio and replacement ratio of blast furnace slag (BFS) on the compressive strength of concrete were first investigated to determine an optimized mixture. Then, using the optimized highstrength concrete (HSC) mixture, hooked steel fibers with various aspect ratios and volume fractions were used as additives and the resulting mechanical properties under compression and flexure were evaluated. Test results indicated that replacement ratios of BFS from 50 to 60% were optimal in maximizing the compressive strength of steam-cured HSCs with various W/B ratios. The use of hooked steel fibers with the aspect ratio of 80 led to better mechanical performance under both compression and flexure than those with the aspect ratio of 65. By increasing the fiber aspect ratio from 65 to 80, the hooked steel fiber volume content could be reduced by 0.25% without any significant deterioration of energy absorption capacity. Lastly, complete material models of steelfiber-reinforced HSCs were proposed for structural design from Lee's model and the RILEM TC 162-TDF recommendations.
high-strength concrete; blast furnace slag; hooked steel fiber; aspect ratio; mechanical property; material model
In recent years, the development of green concrete with
low CO2 emissions has received a great deal of attention
from researchers worldwide
(Bilodeau and Malhotra 2000;
Mene´ndez et al. 2003; Mahmoud et al. 2013; Kinoshita et al.
. The production of Portland cement contributes a large
portion of anthropogenic CO2 emissions; thus, a key
challenge is to reduce the amount of cement used in concrete
mixtures. Replacing Portland cement with mineral
admixtures such as fly ash, blast furnace slag (BFS), and silica
fume has been a widely adopted strategy due to their
pozzolanic reactivity and latent hydraulic activity
(Jeon et al.
2006; Roychand et al. 2016)
. In particular, if the size of
mineral particles is properly determined, then they can be
used to fabricate concrete mixtures stronger than those
without mineral admixtures. High-strength concrete (HSC)
has many advantages for use in precast pre- or
post-tensioned structures, which are normally steam-cured with heat.
Thus, optimized mixtures need to be developed for
steamcured HSCs incorporating high volumes of mineral
HSC is intrinsically brittle, exhibiting low fracture energy.
This has limited the practical applications of HSC in real
civil and architectural structures, and is especially limiting
for designs subjected to tension or flexure. Several methods
have been used to improve the ductility and energy
absorption capacity of concrete, such as adding
discontinuous fibers (i.e. steel, polymeric, and carbon fibers) and
strengthening with fiber-reinforced polymers
Nandakumar 2006; Myers et al. 2008; Kwon et al. 2015;
Yoo and Yoon 2016d)
. The use of discontinuous fibers has
been the most widely adopted method because it is the
simplest and most effective in improving the ductility of
concrete. According to a previous study performed by
Bindiganavile and Banthia (2001)
, the use of steel fibers
improved static post-cracking flexural behavior relative to
polymeric fibers, especially at small deflections, because the
polymeric fibers allowed wider cracks to form that carry
tensile stress further beyond the matrix cracking.
Yao et al.
also reported much better flexural performance in
concretes using steel fibers compared to those using
polymeric fibers. Soroushian and Bayasi (1991) experimentally
investigated the effect of steel fiber shape on the mechanical
properties of concrete, and found that the use of hooked steel
fibers having various aspect ratios was more effective in
improving the flexural strength, energy absorption capacity,
and post-peak ductility under compression than the use of
straight and crimped fibers at identical volume fractions of
2%. Thus, among the various types of steel and polymeric
fibers available, synthetically hooked steel fibers are
expected to be most efficient in improving the flexural
performance of concrete under static loads assuming identical
amount of added fibers.
To allow the practical use of such fiber-reinforced concrete
(FRC) in actual structures, its material models need to be
preferentially proposed. Fibers incorporated into the cement
matrix inhibit crack propagation and widening, leading to
different post-cracking behaviors under compression and
tension compared to those of ordinary concrete without fiber.
For this reason, several researchers
(Barros et al. 2005)
previously used RILEM TC 162-TDF recommendations
, one of the most widely used model codes for
FRC compositions including metallic fibers. However,
RILEM TC 162-TDF recommends the use of a compressive
model of FRC that is identical to that used for ordinary
concrete, even though FRC’s post-peak ductility is
substantially influenced by the fibers
(Yoo et al. 2015)
. Thus, it
is reasonable to develop a model of tensile stress and strain
(TSS) based on RILEM TC 162-TDF and to develop a better
model of compressive stress and strain (CSS) based instead
upon previously suggested compressive models for FRC.
Accordingly, in the present study, the effects of
water-tobinder (W/B) ratio and BFS replacement ratio upon concrete
compressive strength were first examined to determine
optimized mix proportions. Then, the mechanical properties
of the optimized HSC were investigated for various aspect
ratios and volume fractions of hooked steel fiber additive.
Based upon our work, herein we propose complete material
models of steel-fiber-reinforced HSC (SFR-HSC) based on
previous models and the RILEM TC 162-TDF
2. Test Program
2.1 Materials, Mixture Proportions, and Curing
Table 1 details the mixture proportions tested. To obtain
optimized mixture proportions in terms of maximizing early
age compressive strength, three different W/B ratios of 25,
27.5, and 30% and five different ratios of cement
replacement by BFS (0, 40, 50, 60, and 70%) were tested. The unit
water content was held constant at 163 kg/m3, and various
fine aggregate ratios (s/a) from 41 to 44% were used. Type I
Portland cement and Type III BFS were adopted as
cementitious materials; Tables 2 and 3 respectively list their
chemical compositions and physical properties. Type III
BFS was chosen from the economical point of view.
Crushed aggregate was adopted as the fine aggregate, and coarse
aggregate of maximum size 20 mm was also used. A
polycarboxylic acid based air-entraining and water-reducing
admixture was incorporated to attain the required
workability. The workability of concrete without fibers and with
fibers was controlled by 600 and 450 mm slump flow,
To improve the ductility of the optimized low-carbon HSC
mixture containing BFS, hooked steel fibers with two
different aspect ratios were considered: lf/df = 35/0.55 = 65
and lf/df = 60/0.75 = 80, where lf is the fiber length and df
is the fiber diameter. Table 4 summarizes the physical and
geometrical properties of the steel fibers used. The volume
fractions of steel fibers used were 0.5 and 0.75%. For the
optimized mixtures including hooked steel fibers, various
mechanical properties were investigated including
compressive strength, elastic modulus, and flexural performance,
and complete material models for structural design are
suggested herein based on previous work and the RILEM
TC 162-TDF recommendations.
Steam curing with heat was adopted in this study, because
the low-carbon SFR-HSC developed herein is intended for
precast prestressed concrete products. For the first 4 h, all of
the specimens were cured at approximately 20 C with a
relative humidity (RH) of 60%; thereafter, the curing
temperature was increased from 20 to 60 C for 2 h with steam,
and then these conditions were maintained for 6 h. Then, the
temperature was decreased to 20 C using a 3 h ramp, and
the conditions were maintained at 20 C and 60% RH until
the testing date (Fig. 1).
2.2 Test Setup and Specimen Preparation
Five cylindrical specimens for each variable were used in
the compressive strength tests. Specimens were of diameter
100 mm and height 200 mm. Before testing, all cylinders
were ground with a diamond blade to eliminate any
eccentricities. To measure elastic moduli, each specimen was fitted
with a compressometer equipped with three linear variable
differential transformers (LVDTs). A uniaxial load was
applied at the monotonic rate of 0.1 mm/min using a
universal testing machine with the maximum capacity of
250 ton. The compressive tests were carried out according to
; the test setup is shown in Fig. 2.
2.2.2 Four-Point Flexure
Three concrete prisms of cross-section 100 9 100 mm2
and length 400 mm were used for each variable in tests of
flexural properties. To minimize the effects of eccentricities,
all specimens were rotated 90 from their casting surface
before testing. A uniaxial load was applied at the rate of
0.4 mm/min using the same universal testing machine used
for compressive testing. To measure the pure mid-span
deflection without support settlement, a yoke equipped with
one LVDT on each side was installed. A pin-type support was
adopted to maintain the clear span length of 300 mm, to aid
in calculating the flexural strength, and the applied load was
measured using a load cell affixed to the cross head. The
flexural strength was calculated using the equation PL/bh2,
where P is the applied load, L is the clear span length, b is the
beam width, and h is the beam height. The test setup used for
four-point flexural testing is illustrated in detail in Fig. 3.
2.2.3 Three-Point Flexure for Notched Beams
To properly design FRC structures subject to flexure or
tension, a TSS model needs to be proposed for sectional
(Yoo et al. 2016a)
. For this, RILEM TC 162-TDF
proposes a method based on a simple three-point flexural
test. According to the RILEM recommendations, beams of
dimensions 150 9 150 9 550 mm3 were fabricated, and
three specimens were tested for each variable. For
threepoint-flexure tests, a uniaxial load was monotonically
applied at the rate of 0.4 mm/min using the universal testing
machine, conditions identical to those used for the
compressive and four-point flexural tests. A 25 mm notch
was cut into the beam at the middle of its length to induce
the propagation of a single crack, and a yoke with two
LVDTs was also installed to measure the pure mid-span
deflection. During the three-point flexural tests, a roller-type
support was used to eliminate friction between the beam and
the support, as shown in Fig. 4.
(60 C - 6hr)
3. Test Results and Discussion
3.1 Effects of W/B and Replacement Ratio of BFS on Compressive Strength
Compressive strengths were tested and the results are
given in Fig. 5. In the figure and hereinafter, the letters OPC
and BS indicate concrete specimens respectively
incorporating ordinary Portland cement without BFS and
incorporating both OPC and BFS; numbers subsequent to the BS
designation denote the percentage of the BFS replacement
ratio. For example, BS60 indicates concrete with the BFS
replacement ratio of 60%. The compressive strength
generally increased with increasing curing age, because of the
continuous generation of calcium-silicate-hydrate (C-S-H)
owing to cement hydration and pore filling. Normally,
concrete containing both OPC and BS has a higher compressive
strength than concrete made with OPC only. Concrete
containing BS has a higher proportion of the strength-enhancing
C-S-H than concrete made with OPC only. In addition,
cylinders prepared using lower W/B ratios exhibited slightly
higher compressive strengths than their higher-W/B
counterparts with equivalent holding age and BFS replacement
ratios. It is well known that lower W/B ratios yield higher
compressive strengths, owing to their formation of dense,
low-porosity microstructures. Regardless of the W/B ratio,
cylinders including BFS with replacement ratios of up to
60% provided greater compressive strength than those with
OPC only. Interestingly, higher early-age compressive
strengths were also observed for mixtures including BFS,
compared to those without BFS. This finding conflicted with
(Mindess et al. 2003)
that, because of the
latent hydraulic activity of BFS, concrete with BFS normally
exhibits lower strength at early ages, but higher strength
during long-term aging than concrete without BFS. The
main reason why specimens including BFS showed higher
strengths in the present work, even at early ages, is that the
proportion of C-S-H and the apparent activation energy of
concrete increased with increasing BFS replacement ratio,
regardless of the W/B ratio. According to a previous study
Barnett et al. (2006)
, under standard curing
conditions, mortar including BFS exhibited slower strength
development than that of mortar composed of Portland
cement only, whereas under higher curing temperatures, the
strength gain was much faster and the enhancement of
earlyage strength was more significant for cements with higher
BFS replacement ratios, apparently owing to the greater
activation energy. Thus, it can be concluded that replacing
cement with BFS (at B60%) leads to improvement in
compressive strength, both early and long-term aging.
highest compressive strength early (before 7 d), whereas
BS50 showed the highest strength later (after 14 d).
Overall, it was noted that the BFS replacement ratios of
50–60% were most effective in improving the compressive
strength of steam-cured HSC, both early and long-term
40 50 60
Replacement ratio of BFS (%)
40 50 60
Replacement ratio of BFS (%)
40 50 60
Replacement ratio of BFS (%)
The chief aim of the present study was to develop
lowcarbon HSC mixtures for precast prestressed products; thus
the initial strength immediately after heat curing was the
most important parameter. The highest 1-d compressive
strength of 56.7 MPa was obtained from mixture BS60 at
the W/B of 0.275. In addition, when a W/B ratio of 0.25 was
used, the workability was obviously deteriorated and slightly
higher AE agent was required, as compared with W/B ratio
of 0.275 or 0.3. Thus, this mixture was considered optimal
for precast prestressed concrete products in this study.
3.2 Properties of SFR-HSC
ACI Subcommittee 318-F recommended the use of a
minimum fiber volume fraction (Vf) of 0.75% for replacing
minimum shear reinforcement through the use of steel fibers
. Thus, we first used the Vf of 0.75
vol. % of hooked steel fibers having the aspect ratio of 65.
According to previous studies
(Yazıcı et al. 2007; Yoo and
Yoon 2015; Yoo et al. 2016b)
, the use of steel fibers having
higher aspect ratios exhibited better flexural performance
than those having lower aspect ratios. Thus, to investigate
whether the content of hooked steel fibers could be reduced
by increasing the aspect ratio, concrete beams including 0.5
vol.% of hooked steel fibers with the higher aspect ratio of
80 were also prepared and tested. Also, to fundamentally
evaluate how much the flexural performance of HSC beams
could be improved by increasing the fiber aspect ratio, a
specimen containing 0.5 vol.% of hooked steel fibers having
the smaller aspect ratio of 65 was also prepared and tested.
The optimized mixture (BS60 with W/B of 0.275) was used,
and thus the designation system adopted herein for such
samples only specifies the fiber aspect ratio and volume
fraction, as follows: aspect ratio of steel fiber (Sxx)-volume
fraction (0. yy). Herein, xx and yy respectively represent the
aspect ratio and volume fraction. For example, S65-0.75
indicates the specimen including 0.75 vol.% of steel fibers
each having the aspect ratio of 65.
3.2.1 Compressive Behaviors
Compressive stress–strain curves for all test cylinders
were acquired after 28 d and are shown in Fig. 7. To indicate
the effect of including the hooked steel fibers, all
figures include the average compressive stress–strain curve of
the concrete mixture without fiber, designated OPC. Samples
including hooked steel fibers had slightly greater
compressive strength and substantially improved post-peak ductility.
This is consistent with findings by
Ezeldin and Balaguru
, and arises from the steel fibers’ inhibition of crack
propagation and opening.
Table 5 summarizes compressive strength, strain capacity,
and elastic modulus measurements. The specimens including
steel fibers of aspect ratio 65 (S65-0.5 and S65-0.75)
exhibited higher compressive strength, strain capacity, and
elastic modulus compared to that without fiber. Specimen
S80-0.5 exhibited higher strength and elastic modulus but
lower strain capacity than that without fiber. The ascending
stress–strain curve of this specimen was more linear than
that of its counterpart without fiber, because of its inhibition
of micro-crack propagation, but the improvement of
compressive strength was relatively small. In addition, the
microcrack control performance of specimen S80 was worse than
that of specimens S65 because the steel fibers included in
specimen S80 have larger diameter and length than the fibers
included in specimens S65. The smaller fibers can cross
cracks more easily under the condition of same fiber volume
percentage. Thus, it can be noted that the use of hooked steel
fibers with smaller aspect ratios is more effective in
improving the compressive performance of HSC.
To predict the compressive behaviors of SFR-HSC, the
following equation suggested by
Lee et al. (2015)
fc ¼ fc064
a ¼ b ¼
1 þ e0
a ¼ 1 þ 0:723 Vf dlff
for e [ 1:0
where fc0 is the compressive strength, e0 is the strain capacity,
a and b are coefficients, Ec is the elastic modulus, Vf is the
fiber volume fraction of fiber, lf is the fiber length, and df is
the fiber diameter.
In Fig. 7, the dotted line indicates the values predicted by
Eq. (1). An empirical equation proposed by
Lee et al. (2015)
appeared to be appropriate for predicting the compressive
behavior of SFR-HSC with high-volume BFS, for both
ascending and descending branches.
3.2.2 Flexural Behaviors
Curves of flexural load versus deflection are shown in
Fig. 8, and Table 6 summarizes several important
parameters describing the flexural behavior. The flexural strengths
of concrete beams under four-point flexure were calculated
using the equation f = PL/bh2, where P is the applied load,
L is the clear span length, b is the beam width, and h is the
beam height. The specimen without fiber (OPC) exhibited a
sudden load drop immediately after its first cracking. In
contrast, the specimens with fibers sustained the flexural
load well even after the first crack formation, due to fiber
bridging. The specimens including steel fibers (S65-0.5,
S65-0.75, and S80-0.5) showed deflection-hardening
behavior, leading to higher load carrying capacity even after
the first cracking, whereas the OPC specimen demonstrated
deflection-softening behavior. This is supported by the
measured values of deflection capacity (i.e., the deflection
corresponding to the point of flexural strength) given in
Table 6. The deflection capacities of specimens with steel
fibers were much higher than that of the specimen without
fiber. In addition, specimen S80-0.5 demonstrated the
flexural strength of 9.8 MPa, quite similar to that of S65-0.75
(fMOR = 10.0 MPa; fMOR is the post-cracking flexural
strength) and higher than that of S65-0.5 (fMOR = 8.0 MPa).
In addition, specimen S80-0.5 exhibited the largest
deflection capacity of 1.72 mm, owing to its greater length. From
these observation, it can be concluded that the use of hooked
steel fibers with higher aspect ratios is more effective in
improving the flexural strength and deflection capacity.
The toughness values at two deflection points of L/600 and
L/150 were calculated according to ASTM C1609
; L is the clear span length. Because the specimen
without fibers exhibited a sudden load drop immediately
after the first cracking (at 0.063 mm deflection), its
toughness was not calculated. Specimen S65-0.75 exhibited the
highest toughnesses at both deflection points because it had
the largest amount of steel fibers among the specimens
studied. However, specimen S80-0.5 demonstrated
toughness values quite similar to those of S65-0.75 despite its
lower amount of fibers, and showed higher toughness values
than S65-0.5. This indicates that the use of steel fibers with
higher aspect ratios can reduce the amount of fibers needed
without any noticeable reduction of energy absorption
capacity, a finding consistent with previous findings
mentioned above regarding flexural strength and deflection
ACI 318-14 code
indicates that concrete with
steel fibers can be used for shear resistance provided that the
residual strengths, fR, obtained from four-point flexural tests
at the deflection points of L/300 and L/150
are greater than 90 and 75% of the fLOP. Therefore, the
residual flexural stress was also investigated; Table 6
summarizes the results. All test series satisfied the requirements
of the ACI 318 code. This means that SFRC containing 0.5
vol. % of hooked steel fibers having aspect ratios higher than
65 are suitable to be used to impart shear resistance.
Interestingly, the residual flexural strengths were increased more
significantly with increasing fiber aspect ratio than with a
small increase in the amount of steel fibers. Thus, it was
concluded that using steel fibers with higher aspect ratios is
effective in increasing residual strength, affecting shear
resistance, than using those with smaller ones.
3.2.3 Suggestion of Tensile Stress Block for Structural Design
Curves of flexural load versus deflection of large-sized
beams under three-point flexure are shown in Fig. 9. Similar
to the results obtained in four-point flexure testing,
specimens including steel fibers exhibited better post-cracking
flexural behavior than that without fiber, and specimen
S800.5 exhibited similar flexural strength and higher deflection
capacity than specimen S65-0.75, even though its fiber
content was lower. Herein, the flexural strength of
threepoint bending was calculated by using the equation
f ¼ 3PL=2bðh a0Þ2, where a0 is the notch depth.
The flexural strengths at the points of LOP and MOR
obtained in the larger beams were clearly lower than those
obtained in the smaller beams (in Fig. 8). This was mainly
caused by the size effect and restraint of the support.
Decreases in the strength of normal- and high-strength SFRC
beams has been previously reported by Yoo et al. (2016c). In
accordance with Weibull’s size effect theory
fLOP first cracking flexural strength, fMOR post-cracking flexural strength, dMOR deflection capacity, ToughL/600 toughness at L/600, ToughL/150
toughness at L/150, fR,L/300 residual flexural stress at L/300, fR,L/150 residual flexural stress at L/150.
larger specimens are normally weaker than smaller ones
because they have a greater chance to include larger and
more severe flaws. The three-point flexural tests were
performed using a roller-type support to eliminate the support
restraint as per RILEM TC 162-TDF, whereas the four-point
flexural tests were carried out using a pin-type support as per
ASTM C1609. In test results reported by Wille and
ParraMontesinos, the measured flexural strength was clearly
affected by the support conditions: use of the pin-type
support resulted in a higher flexural strength than the roller-type
support due to its restraint by friction
To calculate a tensile stress block, RILEM TC 162-TDF
recommendations were adopted in this study. Firstly,
equivalent flexural strengths were calculated based on
energy absorption capacities, as follows:
where feq,2 and feq,3 are equivalent flexural strength
strengths; DfBZ;2 and DfBZ;3 are the energy absorption
capacities until deflections of d2 and d3 (d2 = dL ? 0.65 mm and
d3 = dL ? 2.65 mm), excluding the triangular area up to the
deflection of 0.3 mm; and dL is the deflection corresponding
to the peak load up to 0.05 mm.
Table 7 lists the calculated parameters. By increasing the
fiber aspect ratio and volume fraction, both the energy
absorption capacities and the equivalent strengths were
improved. The highest value of feq,2 was obtained for
specimen S65-0.75, whereas the highest value of feq,3 was
obtained for specimen S80-0.5. This indicates that using a
higher amount of fibers is effective in improving flexural
performance under small deflections, whereas using longer
fibers is efficient in improving flexural performance under
The following equations were used to obtain tensile stress
versus strain laws; the material modeling is schematically
illustrated in Fig. 10.
Here, fMOR is the flexural strength, d is the effective beam
depth, and Ec is the elastic modulus of concrete.
The calculated TSS models are shown in Fig. 11, and the
parameters are summarized in Table 7. Specimen S65-0.75
exhibited the highest tensile strength of 8.2 MPa, whereas
the highest residual tensile strength, r3, was obtained in
specimen S80-0.5 as 2.8 MPa. This is consistent with the
findings from flexural tests discussed above.
Complete material models under compression and tension
for the SFR-HSC used in the current study were obtained by
using Lee’s compressive model
(Lee et al. 2015)
in Eq. (1)
and the tensile models, suggested by RILEM TC 162-TDF,
with suggested parameters from Table 7. Thus, these models
can be adopted for sectional analysis of structural elements
made of SFR-HSC.
3.2.4 Fracture Energy
In order to compare the fracture energy behaviors of
SFRHSCs according to the crack opening displacement (COD),
the post-cracking tensile stress versus strain curves in
Fig. 11 were transferred to the post-cracking tensile stress
versus COD. For this, the following equation was adopted
from AFGC recommendations
ft;el=Ec þ w=lc, where ft,el is the cracking tensile strength, Ec
is the elastic modulus, w is the COD, and lc is the
characteristic length (=2/3 9 beam height for rectangular
beam). The cumulative fracture energies with COD are
summarized in Fig. 12. It was obvious that the hooked steel
fiber with a higher aspect ratio of 80 exhibited higher
fracture energy capacity than that with a lower aspect ratio of 65,
although the identical fiber volume fraction of 0.5% was
adopted. In addition, the use of higher amount of hooked
steel fibers resulted in an increase in the fracture energy
capacity at the identical aspect ratio of 65. Consequently, the
increases of fiber aspect ratio or amount are able to improve
the fracture energy capacities.
Herein, the effects of W/B ratio and BFS replacement ratio
upon concrete compressive strength were investigated to
determine an optimized mixture. Based on the optimized
mixture, the implications of using hooked steel fibers of
various aspect ratios and volume fractions upon the
mechanical properties of HSC were then evaluated. Lastly,
to design structures made of SFR-HSC, complete material
models of SFR-HSC under compression and tension were
proposed. We made the following conclusions:
1. Concrete mixtures with a lower W/B ratio and higher
replacement ratios of BFS up to 60% exhibited higher
compressive strength than their counterparts. The
optimum BFS replacement ratio varied between 50 and 60%
in terms of the compressive strength developed in
steam-cured HSC both early and during long-term
2. The addition of hooked steel fibers slightly increased the
compressive strength and increased the post-peak
ductility significantly. In addition, the use of hooked steel
fibers with smaller aspect ratios resulted in better HSC
compressive behavior. The overall compressive stress–
strain curve was predicted well by Lee’s model.
3. HSC beams having Vf of 0.5% or more exhibited
deflection-hardening behavior. The use of hooked steel
fibers with the highest aspect ratio tested of 80 was more
effective in improving the flexural strength, deflection
capacity, energy absorption capacity, and residual
strength affecting shear resistance, relative to the use of
hooked steel fibers with a smaller aspect ratio of 65. In
particular, increasing the aspect ratio from 65 to 80
allowed a 0.25% volume reduction of the steel fiber
content without any noticeable deterioration of energy
absorption capacity. Finally, we proposed TSS models
with appropriate parameters for all SFR-HSCs tested,
based on the RILEM TC 162-TDF recommendations.
Fracture energy capacity of SFR-HSC was improved by
increasing the aspect ratio or the amount of hooked steel
This work was supported by the Industrial Strategic
Technology Development Program (10063488,
Development of Earthquake Resisting Reinforced Concrete using
Grade 700 MPa Reinforcing Bars for Enhancement of
Seismic Safety) funded By the Ministry of Trade, Industry
& Energy (MI, Korea).
This article is distributed under the terms of the Creative
Commons Attribution 4.0 International License (http://
creativecommons.org/licenses/by/4.0/), which permits un
restricted use, distribution, and reproduction in any medium,
provided you give appropriate credit to the original author(s)
and the source, provide a link to the Creative Commons
license, and indicate if changes were made.
ACI Committee 318 . ( 2014 ). Building code requirements for structural concrete and commentary . ACI 318-14 and ACI 318R-14 , American Concrete Institute, Farmington Hills, Mich., USA, p 519 .
AFGC. ( 2013 ). Ultra high performance fibre-reinforced concretes . Interim recommendations (p. 358 ). France: AFGC publication.
ASTM C1609/C1609 M. ( 2012 ). Standard test method for flexural performance of fiber-reinforced concrete (using beam with third-point loading) , ASTM International, West Conshohocken, PA, pp. 1 - 9 .
ASTM C 39 /39 M. ( 2014 ). Standard test method for compressive strength of cylindrical concrete specimens , ASTM International, West Conshohocken, PA, pp. 1 - 7 .
Banthia , N. , & Nandakumar , N. ( 2006 ). Crack growth resistance of hybrid fiber reinforced cement composites . Cement and Concrete Composites , 25 ( 1 ), 3 - 9 .
Barnett , S. J. , Soutsos , M. N. , Millard , S. G. , & Bungey , J. H. ( 2006 ). Strength development of mortars containing ground granulated blast-furnace slag: Effect of curing temperature and determination of apparent activation energies . Cement and Concrete Research , 36 ( 3 ), 434 - 440 .
Barros , J. A. , Cunha , V. M. , Ribeiro , A. F. , & Antunes , J. A. B. ( 2005 ). Post-cracking behaviour of steel fibre reinforced concrete . Materials and Structures , 38 ( 1 ), 47 - 56 .
Bilodeau , A. , & Malhotra , V. M. ( 2000 ). High-volume fly ash system: Concrete solution for sustainable development . ACI Materials Journal , 97 ( 1 ), 41 - 48 .
Bindiganavile , V. , & Banthia , N. ( 2001 ). Polymer and steel fiber-reinforced cementitious composites under impact loading-Part 2: Flexural toughness . ACI Materials Journal , 98 ( 1 ), 17 - 24 .
Ezeldin , A. S. , & Balaguru , P. N. ( 1992 ). Normal-and highstrength fiber-reinforced concrete under compression . Journal of Materials in Civil Engineering , 4 ( 4 ), 415 - 429 .
Jeon , J. K. , Moon , H. Y., Ann , K. Y., Kim , H. S. , & Kim , Y. B. ( 2006 ). Effect of ground granulated blast furnace slag, pulverized fuel ash, silica fume on sulfuric acid corrosion resistance of cement matrix . International Journal of Concrete Structures and Materials , 18 ( 2E ), 97 - 102 .
Kinoshita , H. , Circhirillo , C. , SanMartin , I., Utton , C. A. , Borges , P. H. R. , Lynsdale , C. J. , et al. ( 2014 ). Carbonation of composite cements with high mineral admixture content used for radioactive waste encapsulation . Minerals Engineering , 59 , 107 - 114 .
Kwon , K. Y. , Yoo , D. Y., Han, S. C. , & Yoon , Y. S. ( 2015 ). Strengthening effects of sprayed fiber reinforced polymers on concrete . Polymer Composites , 36 ( 4 ), 722 - 730 .
Lee , S. C. , Oh , J. H. , & Cho , J. Y. ( 2015 ). Compressive behavior of fiber-reinforced concrete with end-hooked steel fibers . Materials , 8 ( 4 ), 1442 - 1458 .
Mahmoud , E. , Ibrahim , A. , El-Chabib , H. , & Patibandla , V. C. ( 2013 ). Self-consolidating concrete incorporating high volume of fly ash, slag, and recycled asphalt pavement . International Journal of Concrete Structures and Materials , 7 ( 2 ), 155 - 163 .
Mene ´ndez, G. V. B. B. , Bonavetti , V. , & Irassar , E. F. ( 2003 ). Strength development of ternary blended cement with limestone filler and blast-furnace slag . Cement and Concrete Composites , 25 ( 1 ), 61 - 67 .
Mindess , S. , Young , J. F. , & Darwin , D. ( 2003 ). Concrete (p. 644 ). Upper Saddle River, NJ: Prentice Hall.
Myers , D. , Kang , T. H. , & Ramseyer , C. ( 2008 ). Early-age properties of polymer fiber-reinforced concrete . International Journal of Concrete Structures and Materials , 2 ( 1 ), 9 - 14 .
Parra-Montesinos , G. J. ( 2006 ). Shear strength of beams with deformed steel fibers . Concrete International , 28 ( 11 ), 57 - 66 .
RILEM TC162-TDF. ( 2000 ). Test and design methods for steel fibre reinforced concrete: Bending test . Materials and Structures , 33 , 75 - 81
Roychand , R. , De Silva, S. , Law , D. , & Setunge , S. ( 2016 ). Micro and nano engineered high volume ultrafine fly ash cement composite with and without additives . International Journal of Concrete Structures and Materials , 10 ( 1 ), 113 - 124 .
400 | International Journal of Concrete Structures and Materials (Vol. 11 , No.2, June 2017) Soroushian, P. , & Bayasi , Z. ( 1991 ). Fiber type effects on the performance of steel fiber reinforced concrete . ACI Materials Journal , 88 ( 2 ), 129 - 134 .
Weibull , W. ( 1939 ). A statistical theory of the strength of materials . Proceedings, The Royal Swedish Institute for Engineering Research , 151 (pp. 1 - 45 ).
Wille , K. , & Parra-Montesinos , G. J. ( 2012 ). Effect of beam size, casting method, and support conditions on flexural behavior of ultra-high-performance fiber-reinforced concrete . ACI Materials Journal , 109 ( 3 ), 379 - 388 .
Yao , W. , Li , J. , & Wu , K. ( 2003 ). Mechanical properties of hybrid fiber-reinforced concrete at low fiber volume fraction . Cement and Concrete Research , 33 ( 1 ), 27 - 30 .
Yazıcı , S ¸ ., I˙nan, G., & Tabak , V. ( 2007 ). Effect of aspect ratio and volume fraction of steel fiber on the mechanical properties of SFRC . Construction and Building Materials , 21 ( 6 ), 1250 - 1253 .
Yoo , D. Y. , Banthia , N. , Yang , J. M. , & Yoon , Y. S. ( 2016a ). Size effect in normal- and high-strength amorphous metallic and steel fiber reinforced concrete beams . Construction and Building Materials , 121 , 676 - 685 .
Yoo , D. Y. , Banthia , N. , & Yoon , Y. S. ( 2016b ). Flexural behavior of ultra-high-performance fiber-reinforced concrete beams reinforced with GFRP and steel rebars . Engineering Structures , 111 , 246 - 262 .
Yoo , D. Y. , Kang , S. T. , & Yoon , Y. S. ( 2016c ). Enhancing the flexural performance of ultra-high-performance concrete using long steel fibers . Composite Structures , 147 , 220 - 230 .
Yoo , D. Y. , & Yoon , Y. S. ( 2015 ). Structural performance of ultra-high-performance concrete beams with different steel fibers . Engineering Structures , 102 , 409 - 423 .
Yoo , D. Y. , & Yoon , Y. S. ( 2016 ). A review on structural behavior, design, and application of ultra-high-performance fiber-reinforced concrete . International Journal of Concrete Structures and Materials , 10 ( 2 ), 125 - 142 .
Yoo , D. Y. , Yoon , Y. S. , & Banthia , N. ( 2015 ). Flexural response of steel-fiber-reinforced concrete beams: Effects of strength, fiber content, and strain-rate . Cement and Concrete Composites , 64 , 84 - 92 .