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3rd Conference on Sustainability in Civil Engineering (CSCE’21)
Department of Civil Engineering
Capital University of Science and Technology, Islamabad Pakistan
Paper No. 21-XXX Page 1 of 7
FRESH, MECHANICAL & DURABILITY PROPERTIES OF
POLYPROPYLENE CONCRETE CONTAINING BENTONITE &
SILICA FUME
a Inzimam Ul Haq*, b Ayub Elahi, c Syed Aamir Qadeer Shah, c Malik Ahmad Ghaffar
a: MSc student, Department of Civil Engineering, University of Engineering & Technology Taxila. inzimamsafi@gmail.com
b: Professor at Department of Civil Engineering, University of Engineering & Technology Taxila. ayub.elahi@uettaxila.edu.pk
c: Dy. Chief Engineer (Civil), OGDCL Islamabad. aamirqadeer@ogdcl.com/ahmad_ghaffar@ogdcl.com
Abstract- This paper reports the mechanical & durability properties of bentonite & silica
fume (SF) concrete containing fibrillated micro polypropylene fibers (PPF). The fresh
property was investigated by slump test & mechanical property was investigated by
compressive strength & ultrasonic pulse velocity (UPV) tests. For durability properties,
permeability test was performed. This research is based on the previous published
research & selected the optimum percentages of supplementary cementing material
(SCMs) for bentonite & SF. The concrete mixture consists of total of nine mixes: control
mix (CC), two binary mixes (i.e., 10% bentonite (B10SF0P0), 10% SF(B0SF10P0)),
ternary mix (B10SF10P0), also known as ternary control mix (TCC) & then additional
mixes by adding polypropylene fiber equal to 0%, 0.25%, 0.50%, 0.75%, 1% & 1.25% in
TCC. It was concluded that all the binary and ternary mixes showed decrease in the
workability. The UPV test indicated good quality of concrete for binary mixes and ternary
mixes up to the PPF content equal to 0.75%. It was observed that compressive strength
& permeability properties of concrete were improved for both the binary mixes and
ternary mixes up to addition of PPF equal to 0.5%. PPF increased the deformability
properties & completely changed the failure pattern of concrete as compared to ternary
mix without PPF.
Keywords- Workability, supplementary cementing material, bentonite, compressive
strength, ultrasonic pulse velocity, permeability.
1. Introduction
In the current era, Pakistan is trying to boost their economic state & provide best standard of life to the inhabitant of the
state. To facilitate the public & provide standard of living, different projects are on their track line, like housing, highway,
dam & the most important CPEC projects. For all these infrastructure of development projects, concrete is one of the
abundantly used construction material. Cement is the important constituent of concrete responsible for binding all other
ingredients. All these projects increase the demand of cement [1]. Recently Govt of Pakistan announced to increase the
cement manufacturing industries to fulfil the current huge demand required for infrastructure development. Cement
industry is responsible for consuming large amount of energy & CO2 emission that ultimately causes climatic problem [2].
Supplementary cementing material (SCMs) is one of the solutions to minimize the consumption of natural raw material
for cement, energy consumption & reduce the negative impacts on the environment. Different researchers used SCMs to
investigate fresh properties & hardened properties to study mechanical & durability performance of concrete [3] [4]. The
pozzolanic material can also be added during the manufacturing process of cement at different proportion. Uzal et al [5]
studied the manufacturing laboratory based blended Portland cement by addition of natural volcanic pozzolanic material.
Experimental study was limited to material from two volcanic sources by 55% replacement at different grinding time. The
blended cement improved compressive strength & reduced the ability of alkali silica expansion.
3rd Conference on Sustainability in Civil Engineering (CSCE’21)
Department of Civil Engineering
Capital University of Science and Technology, Islamabad Pakistan
Paper No. 21-XXX Page 2 of 7
Bentonite is a pozzolanic material abundantly available in Pakistan. Different researchers worked on bentonite as a partial
replacement of cement [6] [7]. Memon at al., observed that the particle size of bentonite is flaky & elongated, which tends
to reduce the workability [8]. SF is being used as partial replacement of cement at a certain proportion to increase certain
mechanical & durability properties. From the scanning electron microscopy, it was observed in past research that the use
of silica fume in concrete significantly reduced the porosity & provide dense concrete, which ultimately reduced the
permeability [9]. In another study, SF increased both mechanical & durability properties of concrete due to the formation
calcium silicate hydrate gel (C-S-H) in the result of pozzolanic reaction [10]
The addition of PPF & polyester fibers improved mechanical properties and ductility. In addition, PPF showed greater
ductility than polyester fiber [11]. PPF significantly reduced workability, increased air content, improved ductility of
mortar. Increase in the proportion of PPF, permeability was increased [12]. The combine effect of SCMs improved the
mechanical & durability properties of concrete and different fibers were added to improve the ductility properties [13].
Akbar et al studied the combine effect of Pakistani bentonite & SF on various aspects of high-performance concrete [3].
However, there is limited and contradictory data available in the literature regarding effect of PPF on binary and ternary
mixes of concrete with Bentonite and SF. The proposed study will help the stakeholders of construction industry in using
SCMs and PPF without any hesitation for the intended purpose.
2. Experimental Work
2.1 Materials used
Ordinary Portland cement (OPC) of type-I was used as the main binding material followed by ASTM C150 [14]. Specific
gravity of OPC was 2.99, initial & final setting time was 109min & 285 min respectively. Bentonite & SF was used as a
SCMs. Properties of OPC, Bentonite & SF are shown in the Table 1.
Table 1Properties of OPC, Bentonite & SF
Chemicals
SiO2
TiO2
Al2O3
Fe2O3
MnO
MgO
CaO
Na2O
K2O
P2O3
LOI
OPC
17.4
-
10.2
3.6
-
1.8
62.3
0.9
1.4
0.9
Bentonite
56.8
1.45
15.45
12.27
3.71
0.55
-
-
-
6.89
Silica fume
92.2
2.7
Tap water was used both for mixing & curing of the concrete samples. The addition of both SCMs caused reduction in the
workability. Water- cement ration was kept constants for all mixes. In order to get the required slump, dosage of
superplasticizer was adjusted. Fine aggregate (FA) was used from Lawrencepur source in Pakistan. Coarse aggregate (CA)
from Margalla hills source was used in concrete. The maximum size of coarse aggregate was 19mm. The properties of FA
and CA are shown in the Table 2. PPF of length 19mm was used. Its properties, as reported by manufacturer [15], are
shown in the Table 3.
Table 2. Properties of inert materials Table 3. Properties PPF (Matrixx Company).
Tensile Strength at breakage (MPa)
31-41 [16]
Elongation at break (%)
100-600 [16]
Tensile modulus (MPa)
1137-1551 [16]
Specific gravity
0.9-0.91 [17]
2.2 Mix Proportions
Total nine different mix proportion were used to investigate the mechanical & durability properties of concrete. The
optimum percentage for partial replacement of Bentonite & SF was selected on the basis of previous research [18] [7]. A
total of nine mixes were prepared with a constant water to binder ratio of 0.5. Mixes include CC mix, 10%
bentonite(B10SF0P0), 10% SF (B0SF10P0), ternary mix (B10SF10P0). PPF was then added into the ternary mix with
varying percentages up to 1.25% with an interval of 0.25%.
2.3 Sample preparation
FA
CA
Specific gravity
2.7
2.65
Water absorption (%age)
1.3
0.54
Loose density (Kg/m3)
-
1412
Rodded density (Kg/m3)
-
1550
Fineness modulus
2.99
-
3rd Conference on Sustainability in Civil Engineering (CSCE’21)
Department of Civil Engineering
Capital University of Science and Technology, Islamabad Pakistan
Paper No. 21-XXX Page 3 of 7
Yielding of all the batches of ingredients were done by weight. The ingredients were mixed in an electric concrete mixer
& revolved at a rate of 30 rev/min. To get desired workability, Visconcrete 3110 superplasticizer (SP) was used in the
concrete mixes. Different sample were prepared for different tests. To get the average value of each testing results, three
sample were prepared & tested. Cube of 150x150x150mm was used for compressive strength, whereas, 100x100x150mm
size samples were prepared & tested for permeability results. Fresh property was observed through slump test. Hardened
properties of concrete were investigated by performing mechanical & durability tests. For mechanical properties,
compressive strength was investigated by preparing cubes & ultrasonic pulse velocity test was also performed. For
durability property, permeability test was conducted. The coefficient of permeability was calculated by the following
formula; 𝑘 = Qxh/AxtxP
Where Q=discharge from sample; P is hydrostatic pressure; A is sample top surface area; h is sample height & t is
permeability time.
3.2. Results & discussion
3.1. Fresh properties
3.1.1. Workability
Workability of each mix (with constant water-cement ratio) was determined using slump test according to ASTM C143
[19]. Slump values for varying percentage of Bentonite, SF & PPF were tried to keep constant. Dosage of SP (by %age
weight of binder) reflected that workability was reduced by adding Bentonite and SF. It was concluded from the results
that the addition of bentonite, SF & PPF significantly reduced the workability. Required dosage of SP for Bentonite binary
mix was more as compared to that of SF binary mix, showing comparatively severe effect of Bentonite as compared with
that of SF in reducing workability. However, TCC mix, being highest replacement value among unstrengthen mixes used
combatively high dosage of SP. For other mixes achieved by adding PPF, there was no improvement, even at maximum
permissible dosage of SP. Therefore, Workability results of all the PPF strengthened ternary mix were discarded in the
Figure 1. Because of the fine particle size of bentonite & SF compared to cement particle, reduced slump value was
experienced. The particle shape of bentonite & SF was flaky & spherical respectively. Due to spherical nature, SF showed
better workability than that of Bentonite which is in accordance with other studies [12].
3.2. Mechanical properties
3.2.1. Compressive strength
It is one of the important properties widely used to determine the uniaxial load carrying capacity of concrete. It was
determined on cubes according to BS [20]. The results of compressive strength of cubes are shown in the Figure 2. It was
concluded that PPF increased the ductility properties of concrete. The addition of Bentonite & SF increased the
compressive strength, & PPF showed slightly improvement in the strength up to 0.5% its addition as compared to that of
TCC mix, but further increase in the proportion of PPF caused reduction in the compressive strength which is in accordance
with previous work [21]. Increase in strength by adding PPF up to 0.5% is due to effective bond of PPF with the cement
paste. However, further addition in optimum content of PPF caused decrease in compressive strength. The addition of PPF
completely changed the failure pattern of concrete & there was about half inch deformation without crushing of concrete
as occurred in control mix. The compressive strength of the TCC mix was improved by about 8% as that of control mix at
0
5
10
15
20
25
Compressive
strength(MPa)
28-Days 90-Days
Figure 1. Slump test results
Figure 2. Compressive strength test results
20
30
40
50
60
70
80
Control Mix B10SF0P0 B0SF10P0 B10SF10P0
Slump(mm)
Slump test results with different dosage of SP
SP=0.5%
SP=0.75% SP=0.6% SP=1.0%
3rd Conference on Sustainability in Civil Engineering (CSCE’21)
Department of Civil Engineering
Capital University of Science and Technology, Islamabad Pakistan
Paper No. 21-XXX Page 4 of 7
90 days. PPF up to 0.5% addition showed better results but further increased in proportion decreased the strength & the
mix containing maximum PPF reduced the strength by 44% as compared to the CC mix. When cracks became visible in
the sample, there was no reduction in applied load, but the load became constant & only the strain was increased, after a
short period of time again the load started increasing due to the bond interlocking capacity of the PPF in concrete.
3.2.2. Ultrasonic Pulse Velocity (UPV) Test
The quality of concrete was determined by a non-destructive UPV test by using direct method. A direct pulse transit time
was calculated between the two opposite transducers emitter & receiver by passing sound pulse from one transducer to
receive by other. The propagation of signal was directly noted & velocity was determined by putting the distance between
the transducers. The pulse time taken depends on the uniformity, porosity & cracks availability [22]. From the pulse transit
time, velocities were calculated by dividing the pulse distance by transit time. It was performed for cubes in all the three
planes of the cube to get the average value of the stable pulse time. From this test quality of concrete was investigated from
the velocity of waves. The results of UPV are shown in the Figure 3. From the results it was observed that the addition of
bentonite & SF increased the velocity of signals & PPF reduced its value due to porous nature. All the mixes up to 0.75%
PPF showed good quality of concrete because its UPV value lies in the range 3660-4575m/s [23]. Greater the addition of
PPF fiber, greater was the time to pass the waves in concrete body. It was because of the greater absorption of pulse wave
by PPF & voids developed due to PPF & ultimately it reduced the quality of concrete as compared to CC.
3.3. Durability properties
3.3.1. Permeability
It was observed by an apparatus specially design for permeability test. Samples with sizes of 100x100x150 were prepared
& cured in water for 24 hours and then cured in room temperature in hessian cloth till 72 hours before the age of testing at
28 days & 90 days. The samples were then oven dried by placing it in oven for a period of 48 hours before performing test
on it. The oven dried samples were placed in open air to bring its temperature to atmospheric level & after that they were
painted from all the four sides to retain the penetration of water from the sides and water was made to flow from the top
and bottom side only. Samples were fitted in the machine & open spaces were closed by silicon abrasive to maintain
constant pressure of water & hindering the water to flow out from the sides. After complete dry of silicon, machine was
fixed for performing the test [24]. The results of each mix are shown in the Figure 4. From the results it was observed that
the TCC mix reduced the penetration of water by 42% compared to CC. It was due to dense structure of concrete & the
fine particle of pozzolana. The addition of PPF up to 0.5% contributed in the reduction of permeability & further addition
of PPF in concrete increased the permeability due increased in porosity of concrete [12]. The mix containing maximum
PPF (B10SF10P1.25) increased permeability by 41.5% as compared to CC mix at 90 days curing.
3.4. Correlation between compressive strength & coefficient permeability
The compressive strength & coefficient of permeability of concrete are inter-related & are dependent on each other. As
Bentonite & SF were added into concrete, both compressive strength & coefficient of permeability of concrete were
improved, while the addition PPF contributed further improvement in the properties up to the content of PPF equal to
0.0
500.0
1000.0
1500.0
2000.0
2500.0
3000.0
3500.0
4000.0
4500.0
5000.0
Velocity (m/sec)
28-Days 90-Days
Figure 4. UPV test results
Figure 3. Permeability coefficient of concrete
0.00E+00
1.00E-07
2.00E-07
3.00E-07
4.00E-07
5.00E-07
Coefficient of permeability
(mm/sec)
28-Days 90-Days
3rd Conference on Sustainability in Civil Engineering (CSCE’21)
Department of Civil Engineering
Capital University of Science and Technology, Islamabad Pakistan
Paper No. 21-XXX Page 5 of 7
0.5%. There is a linear relationship between compressive strength & coefficient of permeability of concrete at both the
ages (28 days as well as 90 days) and these results are in agreement with previous study [7] as shown in the
Figure 5. The results at 90-days for PC as well as RC mixes showed better performance as compared to those obtained at
28-days. It was due to the consumption of free calcium hydroxides produced during the hydration reaction, which make
C-S-H gel. This C-S-H gel formation contributed in the strength, durability improvement & made concrete denser.
Figure 5. correlation between compressive strength & permeability test
4. Conclusion
This study investigated the partial replacement of cement by bentonite & silica fume on PPF concrete. the effect of SCMs
& PPF on various parameter of concrete properties such as compressive strength, UPV, permeability was studied. From
the experimental results it was concluded that,
y = -3E-08x + 8E-07
R² = 0.8963
y = -2E-08x + 6E-07
R² = 0.9783
y = -4E-08x + 1E-06
R² = 0.9347
y = -2E-08x + 6E-07
R² = 0.9832
1.00E-07
1.50E-07
2.00E-07
2.50E-07
3.00E-07
3.50E-07
4.00E-07
4.50E-07
10 12 14 16 18 20 22 24
Coefficient of permeability (mm/sec)
Compressive strength (MPa)
28-Days(PC) 28-days(RC) 90-Days(PC)
90-Days(RC) Linear (28-Days(PC)) Linear (28-days(RC))
Linear (90-Days(PC)) Linear (90-Days(RC))
y = -3E-08x + 8E-07
R² = 0.8963
y = -2E-08x + 6E-07
R² = 0.9783
y = -4E-08x + 1E-06
R² = 0.9347
y = -2E-08x + 6E-07
R² = 0.9832
1.00E-07
1.50E-07
2.00E-07
2.50E-07
3.00E-07
3.50E-07
4.00E-07
4.50E-07
10 12 14 16 18 20 22 24
Coefficient of permeability (mm/sec)
Compressive strength (MPa)
28-Days(PC) 28-days(RC) 90-Days(PC)
90-Days(RC) Linear (28-Days(PC)) Linear (28-days(RC))
Linear (90-Days(PC)) Linear (90-Days(RC))
3rd Conference on Sustainability in Civil Engineering (CSCE’21)
Department of Civil Engineering
Capital University of Science and Technology, Islamabad Pakistan
Paper No. 21-XXX Page 6 of 7
1. Compressive strength was increased by addition of SCMs, both Bentonite as well as SF mixes. The ternary
mix (B10SF10P0) increased the strength by 8% as compared to CC mix at the age of 90 days.
2. Coefficient of permeability of concrete of both binary & ternary mixes were decreased as compared to CC
mix. Coefficient of permeability of ternary mix was reduced by 42% as compared with CC mix at 90 days.
3. PPF strengthened ternary mixes, containing PPF up to 0.5%, showed reduction in the coefficient permeability
PPF content as compared to CC mix. Further addition of PPF increased the coefficient of permeability &
ternary mix by 42% as compared with CC mix.
4. The addition of PPF increased the ductility & completely change the failure pattern of concrete during
compression test.
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3rd Conference on Sustainability in Civil Engineering (CSCE’21)
Department of Civil Engineering
Capital University of Science and Technology, Islamabad Pakistan
Paper No. 21-XXX Page 7 of 7
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