MECHANICAL PROPERTIES OF CEMENT MORTAR BY USING POLYETHYLENE TEREPHTHALATE FIBERS

Abstract

During the last three decades, recycled plastic materials have been widely used to reinforce soils and concrete materials. These waste plastics have been used as fibers, aggregates and binders in concrete and mortar components. In Iraq, it has a wide range area of waste plastics especially those that daily used such as plastic bottles. In recent years researchers interested in re-use of waste plastics as construction materials that are remarkable with economic and environmental benefits. This research investigated the utilization of recycled plastic bottles as fiber to reinforce cement mortar. We used fibers made from polyethylene terephthalate (PET) plastic bottles with different size and volume fractions. The main reason of this study was to investigate the effect of the utilization of PET fibers on the mechanical properties of cement mortar. This influence of the PET on the cement mortar has been investigated by applying an experimental programs of compressive strength, splitting tensile strength, ultrasonic pulse velocity and Schmidt tests at 7, and 28 day ages and analyzed in comparison to the control sample. The results show that the incorporation of the fibers improve the splitting tensile strength properties of the cement mortar.

Full text

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MECHANICAL PROPERTIES OF CEMENT MORTAR BY USING
POLYETHYLENE TEREPHTHALATE FIBERS
Hemn U. BOINY*1, Younis M. ALSHKANE2 and Serwan Kh. RAFIQ3
*1Department of Civil Engineering, University of Sulaimani, Iraq.
(E-mail: hemn.ahmed@univsul.edu.iq)
2 Department of Civil Engineering, University of Sulaimani, Iraq.
(E-mail: younis.ali@univsul.edu.iq)
3 Department of Civil Engineering, University of Sulaimani, Iraq.
(E-mail: serwan.rafiq@univsul.edu.iq )
ABSTRACT
During the last three decades, recycled plastic materials have been widely used to reinforce
soils and concrete materials. These waste plastics have been used as fibers, aggregates and
binders in concrete and mortar components. In Iraq, it has a wide range area of waste plastics
especially those that daily used such as plastic bottles. In recent years researchers interested in
re-use of waste plastics as construction materials that are remarkable with economic and
environmental benefits. This research investigated the utilization of recycled plastic bottles as
fiber to reinforce cement mortar. We used fibers made from polyethylene terephthalate (PET)
plastic bottles with different size and volume fractions. The main reason of this study was to
investigate the effect of the utilization of PET fibers on the mechanical properties of cement
mortar. This influence of the PET on the cement mortar has been investigated by applying an
experimental programs of compressive strength, splitting tensile strength, ultrasonic pulse
velocity and Schmidt tests at 7, and 28 day ages and analyzed in comparison to the control
sample. The results show that the incorporation of the fibers improve the splitting tensile
strength properties of the cement mortar.
KEYWORDS: PET fiber, Plastic bottles, Mortar, Compressive Strength, Splitting tensile Strength.
*Corresponding author. Tel.: 00964 (0) 7501119884
E-mail address: hemn.ahmed@univsul.edu.iq, [Hemn U. Ahmed BOINY]

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1 Introduction
During the last three decades, recycled plastic materials have been widely used to reinforce
soils and concrete materials. These waste plastics have been used as fibers, aggregates and
binders in concrete and mortar components [1]. After the polyethylene, the polyethylene
terephthalate forms one of the largest part in solid waste stream [2]. Most of the PET bottles
used for beverage container are thrown away after single usage and disposed PET bottles are
treated by landfill and burning which is create serious environmental problems.
According to the United States Environmental Protection Agency (1992), the municipal solid
waste generated in the U.S.A. is 200, 000,000 tons per year, among them about 8% weight is
plastics [3]. In the year of 1996, content of plastics in municipal solid waste raised to 12%
weight [4]. The world’s annual consumption of plastic materials has increased from around
204 million tons in the 2002 to nearly 300 million tons in 2013 [5]. In Iraq, as in many countries
of the world it has a wide range area of waste plastics especially those that daily used such as
plastic bottles. This type of waste plastics are serious problem for environmental issue because
of its non-biodegradable nature. Recycling of this type of waste plastic to produce new
materials like concrete or mortar appears as one of the best solution, due to its economic and
ecological advantages.
Poly (ethylene terephthalate) (PET) is the most commonly used thermoplastic polyester. PET
is a transparent polymer, with a good mechanical properties and good dimensional stability
under variable load. Moreover, PET has a good chemical resistance and good gas barrier
properties [6].
PET belongs to a thermoplastics with excellent physical properties [7]. It constitutes is around
18% of the total polymers produced worldwide and over 60% of its production is used for
synthetic fibers and bottles, which consume approximately 30% of global PET demand [8].
In recent years researchers interested in re-use of waste plastics as construction materials that
are remarkable with economic and environmental benefits, the studies showed that it was
possible to re-use of waste plastics in concrete and mortar such as polypropylene (PP) [9],
shredded and recycled plastic waste [10], polyethylene terephthalate (PET) [11], , poly vinyl
chloride (PVC) pipe [12], expanded polystyrene foam (EPS) [13], high density polyethylene
(HDPE) [14], thermosetting plastics [15], glass reinforced plastic (GRP) [16]and polycarbonate
as an aggregate, a filler or a fiber [17].Some authors [10, 13] explored, based on waste
polymeric the use of light weight aggregate, as a material in reducing the brittleness, the cost,
the unit weight, thermal insulation properties of building materials such as concrete or mortars.
Polyethylene terephthalate bottles in fiber form can be used to get better the mechanical
properties of concrete such as flexural strength, tensile strength and compressive strength
behavior of concrete [18].
In mortars, the fibers act uniformly distributed reinforcing mortars against the cracks
development due to plastic shrinkage. In the hardened mortar, the uniform distribution of fibers
inhibits the transformation of microcracks in macrocracks thus avoiding a potential for more
serious problems [19]. In hardened composites the cracking sensitivity is function of
deformation due to shrinkage and improved toughness due to incorporation of the fibers [20].
This research investigated the utilization of recycled plastic bottles as fiber to reinforce cement
mortar. We used fibers made from polyethylene terephthalate (PET) plastic bottles with
different size and volume fractions. The main reason of this study was to investigate the effect
of the utilization of PET fibers on the mechanical properties of cement mortar. This influence
of the PET on the cement mortar has been investigated by applying an experimental programs
of compressive strength, splitting tensile strength and ultrasonic pulse velocity tests at 7, 28
day ages and analyzed in comparison to the control sample. The results show that the
incorporation of the fibers improve the mechanical properties of the cement mortar.

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2 Experimental programs and Materials
2.1 Experimental plan
In this research, compressive strength, splitting tensile strength, bulk density, ultrasonic pulse
velocity and Schmidt hammer tests were the experimental programs of recycled polyethylene
terephthalate fiber reinforced cement mortar were conducted.
2.1.1 Compressive strength
The compressive strengths of the cylinder (diameter 50 mm * length100 mm) cement mortar
samples have been tested at 7 and 28 days in accordance with ASTM C39-96 [21].The
specimens were loaded under a compression machine up to failure, the higher tray is fixed and
the lower support is mobile. Before testing, the faces of the specimen were suffered with a
surfacing machine, to ensure parallelism and flatness of the faces of support.
2.1.2 Splitting tensile strength
The splitting tensile strength of the cement mortar were determined at 7 and 28 days, a cement
mortar cylinder in the type which was used for compression tests was placed with it’s the
horizontal axis between the platens of a testing machine according to ASTM C496-04 [22] and
in the form of splitting indirect tension the load is increased until failure along the vertical
diameter takes place.
2.1.3 Bulk density
Characterization of the behavior of the cement mortar was performed through measurements
of the properties of this product in the hardened state, so we determine the mortar density with
a cement mortar cylinder, in the type which was used for compression tests at 7 and 28 days.
2.1.4 Ultrasonic pulse velocity
The principle for applying this test is to measure the velocity of longitudinal waves in cement
mortar samples. The determination consists of measurement of the time taken by a pulse to
travel a measured distance, knowing the distance(s) travelled by the waves, it is possible to
derive a velocity (v) equal to (l/ t) in km/s. The procedure consists in placing sensors on the
sample surface coated with a thin layer of petrolatum; this layer will prevent unwanted waves,
as described in ASTM C597-16 [23]. Measurements are recorded on digital screen at the time
of stabilization.
2.1.5 Schmidt hammer
This test is the widely used as non-destructive tests, the rebound number of the cement mortar
samples were determined in 7 and 28 days, a cement mortar cylinder, in the type which were
used for compression tests, we take the rebound numbers (RN) from different parts of the
cement mortar samples with it’s the horizontal and vertical axis of the samples according to
ASTM C805 / C805M-13 [24].The rebound hammer test is based on the principle that the
rebound of an elastic mass depends on the hardness of the surface against which the mass
impinges[25].
2.2 Materials
A commercial ordinary Portland cement and a locally available natural sand supplied by the
quarry (Darbandikhan, Sulaimaniyah, Iraq) were used to produce the mix of the cement
mortars, with the cement mortar mix proportions (1:2) by weight, ordinary Portland cement
and locally available natural sand. The ordinary Portland cement was having fineness of 10%
in accordance with ASTM C184-94[26], normal consistency was equal to 34% according to
ASTM C187-98[27] and initial and final setting time were 65 minutes and 175 minutes,
respectively in accordance with ASTM C191-99[28]. The fine aggregate having maximum
aggregate size and nominal maximum aggregate size of 4.75mm and 2.36 mm, respectively,
fineness modulus (FM) of 2.20 according to ASTM C33-13[29], Specific gravity for the sand

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was 2.65 in accordance with ASTM C128-97[30].
The plastic fibers were added to the mix by weight of the total weight of the mix, i.e. 0%, 0.5%,
1.0%, 1.5%, 2.0% and 3.0%, we used two different size of the PET fibers, one of them is long
fiber (16.0 mm length and 1.0 mm width) and the other one was short fiber (8.0 mm length
and 1.0 mm width) were obtained by mechanical cutting of lateral sides of PET bottles, the
bottom and necks of the bottles were discarded, and then the PET fibers were introduced in dry
mortars during the mixing, Thus, a hand dry-mixing before the wet mixing in mortar mixer was
conducted for the mortars. For the preparation of the samples after mixing cement mortars, the
molds (cylindrical mold) are met in three phases. For each phase, a compaction of 25 tamped.
For each series, three cylindrical specimens (50mm*100mm) were prepared by using the same
composition. After de-molding, the specimens were deposited in a water until test day, the
samples were tested at 7 and 28 days, the mix proportion are presented in Table 1.
Table 1: Mix proportions of the cement mortar’s (Kg/m3)
Material
0%
PET
0.5% PET
1.0% PET
1.5% PET
1.5%
PET(short
fiber)
2.0% PET
3.0% PET
Cement
629.2
629.2
629.2
629.2
629.2
629.2
629.2
Sand
1258.5
1258.5
1258.5
1258.5
1258.5
1258.5
1258.5
water
295.8
295.8
295.8
295.8
295.8
295.8
295.8
PET
0
9.44
18.88
28.32
28.32
37.76
56.63
Fig.1 short PET fiber Fig.2 long PET fiber Fig.3 Waste plastic bottle
Fig.4 particle size distribution of fine aggregate
3 Results and discussion
The compressive strength results are presented in Table 2. The Table shows that the fibers
incorporation does not increase the magnitude of the mortar compressive strength, while with
decreasing the PET fiber length from 16.0 mm to 8.0 mm the mortar compressive strength is
increased by 15% at 28 day tests. The compressive strength of the cement mortar without fibers
0
20
40
60
80
100
120
0.075 0.15 0.3 0.6 1.18 2.36 4.75 9.5
% Passing
Sieve Size (mm)
Actual sand
ASTM uper
ASTM lower

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increased around 35% at 28 days, by adding 0.5% of the fiber content to the total dry weight
of the mix, it decreases 8.0% of the mortar compressive strength, while by adding 3.0% of the
fiber content, decrease the mortar strength by 100%, and also by increasing the fiber content
from 7 days to 28 days there was not observed significant changes in the compressive strength
results that demonstrate a clear influence of fibers, it is expected that the cement hydration of
mortar samples is slow and the matrix is not significantly strengthen. Fig. 5 shows a typical
failure mode of compression test was obtained with the samples.
Table 2: Mortar uniaxial compression strength (UCS) [Mpa]
The splitting tensile strength of the cement mortars are presented in Table 3, it is clearly
appeared that splitting tensile strengths of the cement mortars were increases of about 18% by
adding 0.5% of the PET fiber, in comparison with the control sample, this is a desirable result
that a mortar with more ductile behavior can be obtained by using waste PET fibers. In same
way while increasing fiber content up to 0.5 % it does not significantly decrease the splitting
tensile strength and improves ductility properties of the cement mortars and also when
decreasing the PET fiber length from 16.0 mm to 8.0 mm the mortar splitting strength is
decrease by 6% at 28 day tests. A sudden failure take place in the case of 0% of fiber, while in
the case of presence of fiber a sudden failure didn’t take place. Fig. 6 shows a typical failure
mode of Splitting tensile strength tests was obtained with the samples.
Table 3: Mortar Splitting Tensile Strength (STS) [Mpa]
Fiber Length (mm)
16.0mm
8.0 mm
Fiber Content %
0
0.5
1.0
1.5
2.0
3.0
1.5
Splitting Tensile Strength (7 day)
2.54
3.11
2.54
2.19
1.99
2.13
2.15
Splitting Tensile Strength (28 day)
3.01
3.55
2.75
3.07
2.23
2.73
2.90
Ratio of (STS/UCS)
0.07
0.09
0.08
0.10
0.08
0.13
0.08
Fig.5 Typical failure of a mortar after compressive test. Fig.6 Typical failure of a mortar after splitting test
Figure 7 presents the results of mortar density with fiber content were computed at 7 and 28
days. The results in Figure 7 show that the inclusion of PET fibers caused a small decrease in
density, such a reduction does not exceed 2.0 % even for 3.0% fiber content. It is concluded
Fiber Length (mm)
16.0mm
8.0 mm
Fiber Content %
0
0.5
1.0
1.5
2.0
3.0
1.5
Compressive Strength (7 day)
32.4
30.1
26.2
26.9
24.5
19.5
27.0
Compressive Strength (28 day)
43.5
40.3
34.9
30.3
28.8
21.6
34.8

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that the PET fibers incorporation, used in this study, did not significantly change the density of
the hardened cement mortar.
Fig.7 Density of Hardened Cement Mortar
The obtained results of the Ultrasonic pulse velocity of different PET fiber compositions are
presented in Figure 8. It is noted that the speed of sound (p-wave) is higher for mortar which
contains a low percentage of waste PET fibers. It is noted that the waste PET fiber mortars
compactness decreases which decreases the speed of sound. This decrease is due to the regular
shapes form of the fibers which increases the volume of voids inside mortar samples.
Fig.8 Ultrasonic Pulse Velocity of Hardened Cement Mortar
The results of the Schmidt hammer or rebound number (RN) of different PET fiber content are
given in the Figure 9. It is noted that the rebound number is a little bit higher for cement mortar
which contains a low percentage of PET fiber, which is the case of the reference concrete (0%
waste). It is noted that the incorporation of waste plastic fibers decrease the hardness of the
surface of the cement mortar compactness which decreases the speed of sound. This decrease
is due to the presence of fibers which increases the volume of voids. Also there is a little
increase by 5.0% of rebound number when decrease the fiber length from 16.0 mm to 8.0 mm.
For different samples of the same fiber content rebound numbers are same this is shows that
the fiber distribution and relative quality of the mortars are uniform.
2070
2080
2090
2100
2110
2120
2130
2140
2150
2160
0 0.5 1 1.5 2 3 short 1.5
DENSITY ( KG/M3)
FIBER CONTENT %
7 Day 28 day
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4
0 0.5 1 1.5 2 3 short 1.5
PULSE VELOCITY ( KM/SEC.)
FIBER CONTENT %
7 Day 28 Day

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Fig.9 Rebound Number (RN) of Hardened Cement Mortar
Figures 10 and 11 present the stress-strain curves of the cement mortar tested in 7 and 28
days, respectively. As can be seen that with increasing the percent of PET fibers the stiffness
of the mortar decreased which increases the ductility of mortar as well as improves the post-
failure behavior.
Fig.10 Stress–Strain Relationship of Hardened Cement Mortar in 7 day
0
5
10
15
20
25
30
0 0.5 1 1.5 2 3 1.5 short
RN Number
Fiber Content %
7 Day 28 Day
0
5
10
15
20
25
30
35
0 0.001 0.002 0.003 0.004 0.005 0.006
Axial stress (MPa)
Axial strain
1.5 % Fiber
2.0 % Fiber
3.0% Fiber
short fiber 1.5%
0.5 % Fiber
1.0 % Fiber
0.0 % Fiber

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Fig.11Stress–Strain Relationship of Hardened Cement Mortar in 28 day
4 Useful correlations
In this study the correlations between nondestructive tests (Ultrasonic and Schmidt hammer)
and destructive tests (uniaxial compression strength and tensile strength) were developed using
simple regression analysis. The correlations of uniaxial compressive strength (UCS) and tensile
strength with p-wave velocity are presented in Figure 12. The correlations of uniaxial
compressive strength (UCS) and tensile strength with Schmidt hammer are presented in Figure
13. It should be noted that the best correlations was between UCS and and P-wave velocity
since the coefficient of determination ( R2) is 0.89 which gives the coefficient of correlation of
0.94. Therfore, this study suggests the exponential correlation between unixail compressive
strength and P-wave velocity for cement mortar with or without fibers. The correlation
equations are presented in Figures 12 and 13 with their coefficient of correlations (R2).
Fig. 12 Correlations of Uniaxial Compressive Strength and tensile strength with Pulse Velocity
0
5
10
15
20
25
30
35
40
45
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007
Axial stress (MPa)
Axial strain
1.5 % Fiber
3.0 % Fiber
2.0 % Fiber
1.0 % Fiber
0.5 % Fiber
0.0 % Fiber
short fiber 1.5 %

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Fig. 13 Correlations of Uniaxial Compressive Strength and tensile strength with Schmidt number (RN)
5 Conclusion
This study investigated the utilization of recycled plastic bottles as fiber to reinforce cement
mortar. We used fibers made from polyethylene terephthalate (PET) plastic bottles with
different size and volume fractions, this influence of the PET on the cement mortar has been
investigated by applying an experimental programs of compressive strength, splitting tensile
strength, ultrasonic pulse velocity and Rebound number tests at 7, 28 day ages and analyzed in
comparison to the control sample. Based on the extensive research work, the following
conclusions can be drawn:
a) The density of hardened mortar is not significantly change by incorporation of PET fibers,
the PET fibers addition causes a small decrease in density of hardened cement mortars.
b) The PET fibers incorporation does not increase the magnitude of the mortar compressive
strength, but with decreasing the PET fiber length from 16.0 mm to 8.0 mm the mortar
compressive strength is increased by 15% at 28 day tests.
c) The splitting tensile strength of the cement mortars are increase of about 18% with respect
to the control sample by adding 0.5% of the PET fiber to the mix, this is a desirable result
that a mortar with more ductile behavior can be obtained.
d) The speed of sound waves (p-wave) is higher for mortar which contains a low percentage
of PET fibers. It is noted that the waste PET fiber mortars compactness decreases which
decreases the speed of sound waves, by adding 3.0% of fibers decreased in p-velocity by
7.0% with respect to the control sample.
e) The rebound number is a little bit higher for cement mortar which contains a low percentage
of PET fibers, whereas by decreasing the length of the fiber from 16.0 mm to 8.0 mm would
increase the rebound number by 5.0%.
f) Uniaxial compressive strength was successfully correlated with P-wave velocity and
Schmidt number for cement mortar of different ages and percentages of plastic fibers using
simple regression analysis.
ACKNOWLEDGEMENTS
The authors would like to acknowledge the contribution of Mr. Arian Omer Mahmood, a
lecturer at Civil Engineering Department of Engineering Faculty at the University of
Sulaimani, to the paper.

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