Roy Belton: The Rheological and Empirical Characteristics of Steel Fibre Reinforced Self-Compacting Concrete with GGBS and PFA

1. 1
Abstract — When testing steel fibre reinforced self-
compacting concrete (SFRSCC) on-site, it is not practical to
determine the fundamental properties of SFRSCC by means of
rheological testing. Therefore, various empirical tests have
been developed to overcome this rheological shortcoming.
These tests attempt to evaluate the workability of SFRSCC for
its successful placement. Within this paper, the focus is on
evaluating both the rheological and empirical parameters of
SFRSCC with both pulverised fly ash (PFA) and ground
granulated blast furnace slag (GGBS) for the partial
replacement of cement (CEM II/A-L). Three self-compacting
mixtures with different PFA and GGBS contents were used as
reference. Each of the concretes were tested with one type of
steel fibre at different contents. This was done to evaluate the
influence of PFA and GGBS on both the rheological and
empirical parameters of SFRSCC. In doing so, therefore, a
correlation between concrete rheology and concrete
workability could be determined. The results show that the use
of PFA and GGBS in SFRSCC caused an overall reduction in
g and an increase in h. In addition, the GGBS degraded the
passing ability of SFRSCC and the workability of SFRSCC is
retained for longer periods after the addition of water when
using 30% PFA and 50% GGBS. Both the slump flow and
slump flow t500 time showed a reasonably good correlation
with, respectively, g and h, 15 minutes after the addition of
mixing water, but a poor correlation existed between both the
empirical and rheological parameters with an increase in time
beyond 15 minutes after addition of mixing water. A good
correlation was shown to exist between the L-box blocking
ratio and the J-ring step of blocking for all the mixtures.
Keywords—Ground granulated blast furnace slag, Pulverised
fly ash, Rheology, Self-compacting concrete, Steel fibres.
I. INTRODUCTION
ELF-COMPACTING CONCRETE (SCC) is defined as a
concrete that possesses both superior flowability and a
high resistance to segregation, which must flow and fill into
all the areas in the formwork, under its own weight, and
without the need for conventional vibrating techniques.
It is well known that the use of steel fibres enhances the
structural performance of concrete, mainly improved rigidity,
resistance to impact and improved resistance to cracking.
Intuitively, these structural enhancements can be achieved in
SCC. However, fibres are known to significantly affect the
workability of concrete.
Various empirical tests have been developed to evaluate the
workability of SCC (such as Slump flow, L-box and J-ring)
concerning its ability to flow and fill into all the areas in the
formwork, while producing an adequate uniform distribution
of constituent materials. It is well known that the slump flow
test is the most widely used test for evaluating the flowability
of SCC. It is a modified version of the slump test, which
measures two parameters: horizontal flow spread and flow
time. The flow spread evaluates unconfined deformability and
the flow time evaluates the rate of deformation within a
confined flow distance.
According to Kasimmohammed (2014), the inverted slump
cone method is the preferred choice in evaluating the
workability of steel fibre reinforced concrete (SFRC) since
steel fibres transmit considerable stability to a fresh concrete
mass, while the inverted slump flow time is recommended
rather than the traditional slump value.
Grunewald and Walraven (2001) investigated the influence
of both different types of fibres and aspect ratios with various
volumetric proportions on the workability of SCC. In all the
mixtures, the authors report stated that the fibre type and fibre
content affects the workability of SCC. Furthermore, a higher
fibre aspect ratio caused a reduction in workability. The aspect
ratio describes the fibre length divided its diameter. Hossain
et al. (2012) discussed the influence of steel fibres on the
rheological properties of SCC. They stated that increasing the
fibre content increases both the plastic viscosity and yield
stress.
Newman and Choo (2003) stated that the use of PFA and
GGBS for the partial replacement of cement reduces the yield
stress, while the use of PFA and GGBS, respectively,
decreases and increases the plastic viscosity.
Tattersall and Banfill (1983) define rheology as the “science
of deformation and flow of matter”. In essence rheology is
concerned with relationships between stress, strain, rate of
strain and time. Concrete possesses a certain resistance to
flow, therefore the application of a certain force is required for
concrete to flow, and that force is known as a shear stress.
Feys et al. (2008) investigated the rheological properties of
SCC and compared their finding with the Bingham model.
The authors reported that the stress-strain relationship of SCC
The Rheological Characteristics of Steel Fibre
Reinforced Self-Compacting Concrete with PFA
and GGBS
Roy P. Belton and Roger P. West
S

2. 2
is nonlinear and, therefore, shows shear thickening behavior,
which can be described by the Hershel-Bulkley model. The
Hershel-Bulkley model can be represented by the following
equation:
τ = τ0 + kγn (1)
where the term τ is the shear stress, τ0 is the yield stress, k is a
constant related to the consistency, γ is the imposed shear
strain rate and n is the flow index which represents shear
thickening (n>1) or shear thinning (n<1) and when n equals 1,
the model takes the form of the Bingham model.
The torque-speed relationship in a rheometer is similar to
the Hershel-Bulkley model, which can be evaluated by
integrating the function speed and torsional motion by the
geometry of the rheometer. This relationship is in the
following form:
T = T0 + ANb (2)
where the term T is the torque, A and b are parameters that
depend on the geometry of the rheometer and the concrete, N
(rev/s) is the speed and T0 (N/m) is the amount of torque
required to shear the concrete. By using equation (2) the
nonlinear relationship of torque to speed can be determined.
Fig. 1. Hershel-Bulkley torque-speed relationship.
Fig. 1 illustrates the Hershel-Bulkley relationship of torque to
speed. The Hershel–Bulkley parameters (A and b) are
determined by plotting ln (T – T0) versus ln N. The constant A
is determined by the intercept on the y-axis (ln T –T0 axis) and
b is the slope of the straight-line relationship. The rheological
parameter g is the intercept of this relationship on the torque
axis and is related to the fundamental parameter of yield
stress. The dashed black line in Fig. 1 is a linear
approximation of the fitted Hershel-Bulkley model, in which
the slope of this line h is related to the fundamental parameter
of plastic viscosity. In this paper, the rheological properties of
all the mixtures were evaluated by the rheological parameters
g and h.
II. MATERIALS AND METHODS
A. Experimental program on SFRSCC with PFA and GGBS
Three self-compacting reference mixtures were developed
with different compositions. Table 1 summarises these
different compositions.
Table 1: Mixturecomposition for all reference mixtures
Component
Series 1
(kg/m3
)
Series 2
(kg/m3
)
Series 3
(kg/m3
)
CEM II/A-L 580 406 290
Limestone filler 20 20 20
GGBS - - 290
PFA - 174 -
Fine aggregate 1020 1020 1020
Coarse aggregate 630 630 630
Superplasticiser (Glenium 27) 12.5 12.5 12.5
Stabiliser (RheoMatrix100) 7.8 7.8 7.8
Water 215.5 215.5 215.5
Initially, it was assumed that the steel fibres would reduce the
workability. Therefore, it was necessary to design a self-
compacting reference mixture with a high degree of
flowability. For this reason, both the paste and mortar content
were varied by increasing the ratio of sand to aggregate and
increasing the cement content, while the contents of water,
superplasticiser and stabilizer were adjusted by trial and error
to obtain both a high slump (700 mm) and high passing ability
(J-ring: 7.25 mm). Table 1 summarises the final mix design.
Next, to evaluate both the empirical and rheological
parameters of SFRSCC various steel volumetric proportions of
steel fibres were incorporated into each reference mix. Table 2
lists all the SFRSCC mixtures as part of this experimental
program. Three SCC and 18 steel fibre reinforced mixtures
were tested.
Table 2: Experimental program
Steel fibre type
Steel fibre content
SCC-Series 1
(R 65/35)
SCC-Series 2
(R 65/35)
SCC-Series 3
(R 65/35)
0 (kg/m3
) (REF) o o o
5 (kg/m3
) o o o
10 (kg/m3
) o o o
15 (kg/m3
) o o o
20 (kg/m3
) o o o
25 (kg/m3
) o o o
30 (kg/m3
) o o o
To verify the obtained empirical and rheological parameters,
cubes were cast for each mixture and tested at seven-day
compressive strengths. The compressive strengths for series 1
and series 2 ranged from, respectively, 64.7 – 68.1 Mpa and
33.9 – 36.8 Mpa, while series 3 ranged from 52.1 – 56.3 Mpa.
Torque(N/m)
Speed (rev/s)
Slope = h
T = To + ANb
g
Linear approximaton of
Hershel-Bulkley model

3. 3
B. Materials
The cement used throughout this experiment was CEM
II/A-L, while also using PFA, GGBS and limestone filler
(LS). The volume ratio of both the PFA GGBS was kept
constant at, respectively, 70:30 and 50:50, and 95:05 for the
LS. Fig. 1 shows the particle size distributions of all the
powders used in this experiment.
Fig. 2. Particle size distribution of powders
A Glenium 27 superplasticiser based on chains of a modified
Polycarboxylic ether complex was used to achieve an
adequate workability. RheoMatrix 100, an aqueous solution of
a high-molecular weight synthetic copolymer was used to
modify the viscosity and cohesion of the mixtures. Ordinary
tap water was used as mixing water in all the mixtures. One
steel fibre (SF) type with hooked ends (R 65/35) were used in
all the SFRSCC mixtures. The 65 is the aspect ratio and the 35
in the fibre length in mm. Both locally available sand and
gravel were used. Crushed stone aggregates of nominal
maximum size 10 mm were used as coarse aggregates. Fig. 3
shows the particle size distributions of all the aggregates.
Fig. 3. Particle size distribution of the aggregates
C. Mix procedure
A free-fall mixer was used throughout this study. The
following mix procedure was adopted:
 Coarse aggregates and 40% water for 10 s.
 Fine aggregates and powders for 60 s.
 Superplasticiser and 50% water for 20 s.
 Stabiliser and 10% water for 20 s.
 Resting period of 600 s.
 Mixing period of 60 s.
 Steel fibres for 60 s.
D. Test methods
The quantitative empirical tests used in this experiment
were the slump flow, L-box and J-ring. The inverted slump
flow cone method was used in this experimental program.
After lifting the slump flow cone, the slump flow is the mean
horizontal flow spread and the t500 time is the time taken to
reach a flow spread of 500 mm. Both the L-box and J-ring
Fig. 4. Empirical test methods: (i) L-box (ii)Slump flowand (iii) inverted J-
ring.
were used to assess the passing ability. The concrete in the L-
box is placed in the vertical channel. Opening the gate allows
the concrete to flow through the vertical bar spacings and into
the horizontal channel, the height of concrete in both the
vertical and horizontal channel are then expressed as a ratio,
known as the passing ratio, where an acceptable passing ratio
ranges from 0.8 – 1.0. In the J-ring, the inverted cone is lifted,
the t500 time recorded, that is, the time for the concrete to reach
a 500 mm spread distance and its passing ability is assessed by
the average height of concrete at four points around the ring
minus the height at the central position and expressed in mm,
where an acceptable passing value ranges from0 – 10 mm.
The rheological tests were performed with the Tattersall Two-
point workability apparatus (TWT), in particular, the MK II
model, which involves an axial impeller with four angled
blades positioned in a helical arrangement around a central
drive shaft. The schematic diagram is shown in Fig. 5.
According to Tattersall and Banfill (1983) this helical
arrangement raises the concrete while also allowing the
concrete to fall back through the gaps, i.e., minimises the
effects of both segregation and bleeding. A cylindrical bowl
containing the concrete is supported by means of an adjustable
arm. This allows the concrete sample to be raised and
supported both during testing and following the testing
0
10
20
30
40
50
60
70
80
90
100
0.0001 0.001 0.01 0.1 1
PERCENTAGEPASSING%
PARTICLE SIZE (MM)
GGBS
CEM II/A-L
Fly-ash
LS
0
10
20
30
40
50
60
70
80
90
100
0.01 0.1 1 10 100
PERCENTAGEPASSING%
PARTICLE SIZE MM
Sand B & Coarse
aggregates
Sand B
Series 1
Series 2
Series 3

4. 4
regime. The effective height between the top of the bowl and
the shearing surface is 75 mm. Before initiating the testing
regime, the apparatus must run for 30 minutes to allow the oils
(both hydraulic and gear) to reach their operating
temperatures, and
Fig. 5. Schematic diagram of TWT.
during the warmup period, the recommended speed is 0.7
rev/s. However, Tattersall (2003) recommended speeds of 3.0
rev/s because at a warmup speed of 0.7 rev/s the idling
pressure can change even after 80 minutes. In essence, the
torque-speed relationship for the concrete undergoing testing
is determined by reducing the speed (rev/s) from 0.7 to 0.3
rev/s at various speed intervals, while recording the resulting
pressure (lb/in2) at these intervals of speed. In doing so, the
torque intercept and slope and, therefore, the rheological
parameters g and h are determined.
The following testing regime was performed in order to
determine the influence of time on both the empirical and
rheological parameters, that is, an increase in time after the
addition of both mixing water and cementitious materials.
Table 3: Testingregimefortime evolutionof empiricalandrheological
parameters.
Sequence
Regime-1 (15
min after
addition of
water)
Regime-2 (30 -
65 min after
addition of
water)
Regime-3 (65 -
95 min after
addition of
water)
1 TWT TWT TWT
2 Slump flow Slump flow Slump flow
3 L-box L-box L-box
4 J-ring J-ring J-ring
First, the rheological parameters g and h were determined with
the TWT apparatus, then followed by the empirical tests, i.e.,
Slump flow, L-box and J-ring. This was carried three times at
different times after the addition of mixing water. Table 3 lists
the three testing regimes and sequence of tests.
Immediately after each test (i.e. TWT, Slump flow, L-box,
J-ring) for all the mixtures, the concrete was remixed in the
mixer with the remaining concrete for approximately 15 – 20
s, in order to try and eliminate the effects of segregation cause
by the MK II apparatus and to promote an even distribution of
fibres throughout all the mixture undergoing testing.
III. RESULTS AND DISCUSSION
A. Effect of SF, PFA and GGBS on rheology
Rheological testing was performed on all the mixtures, 15
min after the addition of mixing water. In considering all the
possible functional relationships for all the mixtures, the
polynomial function seems to produce the best fit correlation
between torque and speed. The slopes of these relationships
and, therefore, the h parameters were determined by a linear
approximation of the fitted Hershel-Bulkley model.
Fig. 9. FittedHershel-Bulkleymodels for SCC-1 toSCC-7, 15 min after the
addition of water.
As the torque-speed relationships for all the mixtures showed
nonlinear behavior, the Hershel-Bulkley model was used to
represent these relationships. Fig. 9 – Fig. 11 illustrates these
fitted Hershel-Bulkley relationships for all the mixtures
corresponding to a TWT carried out 15 min after the addition
of water. In Fig. 9 – Fig. 11, SCC-1 to SCC-7 represents
series-1 with 0kg/m3 – 30kg/m3 of SF, SCC-8 to SCC-14
represents series-2 with 0kg/m3 – 30kg/m3 of SF and SCC-15
to SCC-21 represents series-3 with 0kg/m3 – 30kg/m3,
respectively.
Fig. 10. FittedHershel-Bulkleymodels for SCC-8 to SCC-14, 15 min after
the addition of water.
0
1
2
3
4
5
6
7
8
9
10
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3
Torque(N/m)
Speed (rev/s)
SCC-1, 15 min
SCC-2, 15 min
SCC-3, 15 min
SCC-4, 15 min
SCC-5, 15 min
SCC-6, 15 min
SCC-7, 15 min
Series 1 (CEM II/A-L)
0 kg/m3 SF
5 kg/m3 SF
10 kg/m3 SF
15 kg/m3 SF
20 kg/m3 SF
25 kg/m3 SF
30 kg/m3 SF
0
1
2
3
4
5
6
7
8
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3
Torque(N/m)
Speed (rev/s)
SCC-8, 15 min
SCC-9, 15 min
SCC-10, 15 min
SCC-11, 15 min
SCC-12, 15 min
SCC-13, 15 min
SCC-14, 15 min
Series 2 (PFA)
0 kg/m3 SF
5 kg/m3 SF
10 kg/m3 SF
15 kg/m3 SF
20 kg/m3 SF
25 kg/m3 SF
30 kg/m3 SF
TWT bowl
Vane arrangement
Speed gauge
Pressure gauge
Rack and pinion

5. 5
Fig. 11. FittedHershel-Bulkleymodels for SCC-15 toSCC-21, 15 min after
the addition of water.
From Fig. 9 – Fig. 11, it may be observed that the rheological
parameters g and h are increasing with an increase in steel
fibre content. The variation of g and h with steel fibre content
is presented in Fig. 12 and Fig. 13. The x-axis in both Fig. 12
and Fig. 13 represents the steel fibre content, i.e., 0kg/m3 –
30kg/m3.
Fig. 12. Effect of PFA and GGBS on the rheological parameter g, 15 min
after the addition of mixing water.
Fig. 13. Effect of PFA and GGBS on the rheological parameter h, 15 min
after the addition of mixing water.
It may be observed that, in both cases, the rheological
parameters g and h increase with an increase in steel fibre
content. In addition, the parameter g decreases when using
PFA and GGBS CEM II/A-L cement replacements in
SFRSCC. However, the parameter g is somewhat constant for
both the SFRSCC and the SFRSCC with 50% GGBS CEM
II/A-L replacement at SF contents ranging from 0 – 15kg/m3.
In Fig. 13, it may be observed that the parameter h increases
when using 30% PFA and 50% GGBS CEM II/A-L
replacements in SFRSCC.
Fig. 14 – Fig. 16 illustrates the variation of g and h with
increasing steel fibre contents for SCC-1 to SCC-21. In
addition, the obtained correlation coefficients for SCC-1 to
SCC-21, 15 min after the addition of water are illustrated. As
shown in Fig. 14, a second order polynomial function seems to
yield the best-fit correlation between the rheological
parameters g and h, with a best-fit correlation, R2, of 0.855. It
is the author’s opinion that the obtained rheological
parameters (g and h) associated with SCC-7 are most likely
underestimated, because during testing a significant degree of
segregation was encountered. Nevertheless, the results for
SCC-7 were included in this analysis.
Fig. 14. Variation of g and h with increasing steel fibre (SF) contents for
SCC-1 to SCC-7, 15 min after the addition of water.
Fig. 15. Variation of g and h with increasing steel fibre (SF) contents for
SCC-8 to SCC-14, 15 min after the addition of water.
From Fig. 14 – Fig. 15, it may be observed that an exponential
function seems to yield the best fit correlation between g and h
for SCC-8 to SCC-13, and SCC-15 to SCC-20 with best fit
correlations of, respectively, 0.841 and 0.708. Also, the
torque-speed relationships and, hence, the obtained parameters
g and h for SCC-14 and SCC-21 were not included in this
0
2
4
6
8
10
12
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3
Torque(N/m)
Speed (rev/s)
SCC-15, 15 min
SCC-16, 15 min
SCC-17, 15 min
SCC-18, 15 min
SCC-19, 15 min
SCC-20, 15 min
SCC-21, 15 min
Series 3 (GGBS)
0 kg/m3 SF
5 kg/m3 SF
10 kg/m3 SF
15 kg/m3 SF
20 kg/m3 SF
25 kg/m3 SF
30 kg/m3 SF
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 5 10 15 20 25 30
Rheologicalparameter,g
Steel fibre content (kg/m3)
SFRSCC
SFRSCC with PFA
SFRSCC with GGBS
0
1
2
3
4
5
6
7
0 5 10 15 20 25 30
Rheologicalparameter,h
Steel fibre content (kg/m3)
SFRSCC
SFRSCC with PFA
SFRSCC with GGBS
20 kg/m3 SF
0 kg/m3 SF
5 kg/m3 SF
10 kg/m3 SF
15 kg/m3 SF
25 kg/m3 SF
30 kg/m3 SF
h = 1.939g2 - 2.764g+ 3.601
R² = 0.855
0
1
2
3
4
5
6
7
8
0 0.4 0.8 1.2 1.6 2 2.4
Rheologicalparameter,h
Rheological parameter, g
Series1 (CEM II/A-L)
0 kg/m3 SF
5 kg/m3 SF
10 kg/m3 SF
15 kg/m3 SF
20 kg/m3 SF
25 kg/m3 SF
30 kg/m3 SF
h = 2.923e0.386g
R² = 0.841
3
3.2
3.4
3.6
3.8
4
4.2
4.4
4.6
4.8
0.4 0.6 0.8 1 1.2 1.4
Rheologicalparameter,h
Rheological parameter, g
Series2 (PFA)

6. 6
analysis, as the obtained torque-speed relationship for these
data points possessed a significant degree of nonlinearity,
which is an indication of segregation. Furthermore, during
rheological testing a high degree of segregation was
encountered (i.e., there was a significant amount of coarse
aggregates and steel fibres stuck to the bottom of the mixing
bowl) in SCC-14 and SCC-21, 15 min after the addition of
water.
Fig. 16. Variation of g and h with increasing steel fibre (SF) contents for
SCC-15 to SCC-21, 15 min after the addition of water.
B. Empirical and rheological parameters for SFRSCC
The relationship between the J-ring step of blocking and L-
box blocking ratio for all the mixtures (i.e. 15 to 95 min after
the addition of water) is presented in Fig. 17. From Fig. 17, it
may be observed that a linear relationship exists between these
empirical values with a correlation coefficient (R2) of 0.83 and
a coefficient of variation of -2.13, which suggests that the J-
ring step of blocking is inversely related to the L-boxblocking
ratio. Therefore, as the J-ring step of blocking (mm) decreases,
L-box ratio increases. The following empirical relation may be
obtained by least square regression:
LB = 1.09-0.029(JR) (3)
where JR is the J-ring step of blocking in mm and LB is the L-
box blocking ratio.
Fig. 17. Variation ofJ-ring step of blocking with L-box blocking ratio for
SCC-1 to SCC-21, 15 to 95 min after the addition of water.
The variation of slump flow and slump flow t500 time with,
respectively, g and h is presented in Fig. 18 and Fig. 19. From
Fig. 18, it may be observed that a poor relationship exists
between slump flow and g, 15 to 95 min after the addition of
water with a correlation coefficient (R2) of 0.22 and a
coefficient of variation (CV) of -9.98. From Fig. 19, it shows a
correlation coefficient of 0.3 and a coefficient of variation of -
1.0 between slump flow t500 time and h for all the mixtures
tested at 15 to 95 min after the addition of water.
Fig. 18. Variation ofSlump flowwith gfor SCC-1 to SCC-21, 15 to 95 min
after the addition of water.
Fig. 19. Variation ofSlump flowt500 time with h for SCC-1 to SCC-21,15 to
95 min after the addition of water.
The variation of J-ring step of blocking with blocking ratio, 15
min after the addition of water is presented in Fig. 20. It may
be observed that there exists a linear relationship between
these empirical parameters with a correlation coefficient (R2)
of 0.9. In addition, the obtained coefficient of variation (CV)
is -1.043, which suggests that the J-ring step of blocking is
inversely related to the L-box blocking ratio. Therefore, as the
J-ring step of blocking (mm) decreases, L-box ratio increases.
The following empirical relation may be obtained by least
square regression:
LB = 1.098-0.027(JR) (4)
0 kg/m3 SF
5 kg/m3 SF
10 kg/m3 SF
15 kg/m3 SF
20 kg/m3 SF
25 kg/m3 SF
30 kg/m3 SF
h = 4.362e0.272g
R² = 0.708
4
4.5
5
5.5
6
6.5
7
0.6 0.8 1 1.2 1.4
Rheologicalparameter,h
Rheological parameter, g
Series3 (GGBS)
LB = -0.029JR+ 1.09
R² = 0.83
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80
L-boxblockingratio(H2/H1)
J-ring, step of blocking(mm)
SCC-1 to SCC-21, 15 min
SCC-1 to SCC-21, 30 - 65 min
SCC-1 to SCC-21, 60 - 95 min
SCC-7, 95 min
CV = -2.13
SF= -35.47g + 734.7
R² = 0.22
500
550
600
650
700
750
800
0 1 2 3 4
Slumpflowspread(mm)
Rheological parameter, g
SCC-1 to SCC-20, 15 min
SCC-1 to SCC-20, 30 - 65 min
SCC-1 to SCC-20, 60 - 95 min
CV = -9.98
SF, t500 = 0.614h + 0.837
R² = 0.30
0
2
4
6
8
10
12
0 2 4 6 8 10
Slumpflow,t500time(sec)
Rheological parameter, h
SCC-1 to SCC-20, 15 min
SCC-1 to SCC-20, 30 - 65 min
SCC-1 to SCC-20, 60 - 95 min
CV = 1.0

7. 7
where JR is the J-ring step of blocking in mm and LB is the L-
box blocking ratio.
Fig. 20. Variation ofL-boxwithJ-ringforSCC-1 to SCC-21, 15minafterthe
addition of water.
The variation of slump flow and slump t500 time with,
respectively, g and h is presented in Fig. 21 and Fig. 22. It
may also be observed from Fig. 21 that there exists a linear
relationship between slump flow and g with an obtained
correlation coefficient (R2) of 0.8 and a coefficient of variation
(CV) of -4.57, which suggests that g is inversely related to
slump flow.
Fig. 21. Variation ofSlump flowwith rheological parameter g for SCC-1 to
SCC-21, 15 min after the addition of water.
As the rheological parameter g decreases, slump flow
increases. In addition, the obtained parameters g and h for
SCC-7 and SCC-21 were not included in this analysis, as a
significant amount of coarse aggregates and steel fibres had
settled to the bottom of the TWT bowl. The following
empirical relation may be obtained by least square regression:
SF = 730.9-43(g) (5)
where SF is the slump flow in mm and g is the rheological
parameter in N/mm, which is related to yield stress.
It may be observed from Fig. 22 that there also exists a
relationship between slump flow t500 time and h with a
correlation coefficient of 0.835 and a coefficient of variation
of 0.72, which suggests that the slump flow t500 time is
positively related to the rheological parameter h. Therefore,
the following empirical relationship may be obtained by least
square regression:
h = 1.63(t500)-0.68 (6)
where h is the slope of the torque-speed relationship (i.e., the
slope of the linear approximation of the Hershel-Bulkley
model, which is related to plastic viscosity and t500 is the
slump flow t500 time in seconds.
Fig. 22. Variation ofSlump flowt500 time with h for SCC-1 to SCC-21, 15
min after the addition of water.
IV. CONCLUSIONS
Based on the results presented in this paper, the following
conclusion can be drawn:
 There is a good correlation between the J-ring step
of blocking and L-box blocking ratio for all the
mixtures at testing times corresponding to 15 to 95
min after the addition of both mixing water and
cementitious materials. J-ring step of blocking
decreases linearly as L-box blocking increases.
 A good correlation between inverted slump flow
and g for all the mixtures, 15 min after the addition
of both mixing water and cementitious materials.
Also, the parameter g decreases as inverted slump
flow increases.
 A good correlation between inverted slump flow t500
time and h, 15 min after the addition of water and
cementitious materials. In addition, the parameter h
increases as inverted slump flow t500 time increases.
 There is a poor correlation between g and inverted
slump flow, h and inverted slump flow t500 time, 15
to 95 min after the addition of water and
cementitious materials.
 The rheological parameters g and h increased with
an increase in steel fibres content. In addition, there
SCC-1
SCC-2
SCC-3
SCC-4
SCC-5
SCC-6
SCC-7
SCC-8
SCC-9
SCC-10
SCC-11
SCC-12
SCC-13
SCC-14
SCC-15
SCC-16
SCC-17
SCC-18SCC-19
SCC-20
SCC-21
LB = -0.0272JR + 1.098
R² = 0.9
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15 20 25 30 35 40
L-boxblockingratio(H2/H1)
J-ring, step of blocking(mm)
CV = -1.043
SCC-1
SCC-2
SCC-3
SCC-4
SCC-5
SCC-6
SCC-7
SCC-8
SCC-10
SCC-9
SCC-11
SCC-12
SCC-13
SCC-15
SCC-16
SCC-17
SCC-18
SCC-20
SCC-19
SCC-14
SCC-21
SF= -43g + 730.9
R² = 0.8
640
650
660
670
680
690
700
710
720
730
0.00 0.50 1.00 1.50 2.00 2.50
Slump-flowspreadvalue(mm)
Rheological parameter, g
CV = -4.57
SCC-1 SCC-2
SCC-3
SCC-4
SCC-5
SCC-6
SCC-7
SCC-8
SCC-9
SCC-10
SCC-12
SCC-11
SCC-13
SCC-15
SCC-16
SCC-17
SCC-18
SCC-19SCC-20
SCC-14
SCC-21
h = 1.63t500 - 0.68
R² = 0.835
0
1
2
3
4
5
6
7
8
9
0 1 2 3 4 5 6
Rheologicalparameter,h
Slump-flow, t500 time (sec)
CV = 0.72

8. 8
is a good correlation between the relative parameters
g and h with increasing steel fibre contents.
 Using 30% PFA and 50% GGBS CEM II/A-L
cement replacements reduced the parameter g, while
causing an increase in h.
 The workability of SFRSCC is retained for longer
periods when using 30% PFA and 50% GGBS CEM
II/A-L cement replacements.
V. REFERENCES
[1] Kasimmohammed, A. (2014). Flexural and shear
performance of high dosage steel fibre reinforced
concrete in suspended slabs.
[2] Grünewald, S., and Walraven, J. C. (2001). Parameter-
study on the influence of steel fibres and coarse
aggregate content on the fresh properties of self-
compacting concrete. Cement and Concrete
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[3] Hossain, K. M. A., Lachemi, M., Sammour, M., and
Sonebi, M. (2012). Influence of Polyvinyl Alcohol, Steel,
and Hybrid Fibres on Fresh and Rheological Properties of
Self-Consolidating Concrete. Journal of Materials in
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[4] Newman, J., and Choo, B. S. (Eds.). (2003). Advanced
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[5] Tattersall, G. H., and Banfill, P. F. G. (1983). The
rheology of fresh concrete (No. Monograph). Pitman
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[6] Feys, D., Verhoeven, R., and De Schutter, G. (2008).
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929.
[7] De Schutter, G., Gibbs, J., Domone, P., and Bartos, P. J.
(2008). Self-compacting concrete. Whittles Publishing.
[8] Tattersall, G. H. (2003). Workability and quality control
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