The First International Conference for Engineering Researches

March 2017

Some Properties of Sustainable Concrete with Plastic Waste

Aggregate Dr. Wasan Ismail Khalil 1, Khalaf Jumaa Khalaf 2

Professor in Building and Construction Engineering Department/University of Technology-

Baghdad- Iraq1

M.Sc. (Eng), 2

Abstract: Significant amounts of non-biodegradable solid plastic waste as by-products from

industrial activities and in disposal areas of waste are found in Iraq, all these waste lead to

environmental pollution. The present study covers the use of different volumetric replacement of

coarse PET shredded plastic waste bottles (10%, 20%, 30%, 40%, and 50%) as a replacement to

natural coarse aggregates to produce sustainable concrete. The experimental tests are involve the

workability, fresh density, water absorption, dry density, ultrasonic pulse velocity, compressive

strength, splitting tensile strength, flexural strength, and static modulus of elasticity. Despite of

some drawbacks like a decrease in compressive, splitting tensile and flexural strength, the use of

plastic waste aggregate presents various advantages. One of these advantages is that the use of

plastic aggregates results in the production of lightweight concrete depends on the content of plastic

waste used. For high contents of coarse PET plastic waste of 40% and 50% as volumetric

replacement to natural coarse aggregate, the dry density was 1910 and 1850 kg/m3 respectively.

These concrete mixes can be classified as lightweight concrete.

Keywords: Sustainable concrete, Mechanical properties, PET plastic waste aggregate.

I. INTRODUCTION

Conventional concrete typically contains about 12% cement and 80% aggregate by mass [1]. The

use of cement is a main contributor to high-energy usage, CO2 and dust emissions, natural resource

depletion, air pollution, ozone layer destruction, global warming, and continuous environmental

deterioration. In recent years, augmentation of plastic consumption is observed all over the world,

which increases plastic production and this leads to increase the plastic waste materials. These

waste materials are now cause environmental pollution. The slow degradation of waste plastic

materials causes a waste disposal crisis from environmental view point. Plastic is consisting of

The First International Conference for Engineering Researches

March 2017

many venomous chemical materials, and therefore plastic causes pollution of, air, water, and soil.

Varieties of toxic chemicals are released into the air during the burning process of plastic wastes,

such as dioxins, which is one of the most poisonous materials. Recently, significant attention has

been given to the use of plastic wastes in concrete industry. The recycled and reused of plastic

waste in construction materials, such as concrete, has many advantages including, the reduction in

the cost of concrete production and disposing of plastic waste [2]. The substitution of natural

aggregate in concrete by waste materials can consume vast amounts of these waste materials. This

can solves problems of aggregate lack in construction sites and reduces environmental problems

related to aggregate mining and waste disposal [3]. The incorporation of plastics in concrete can

significantly improves some properties of concrete, as plastic has high toughness, good abrasion

behaviour, low thermal conductivity and high heat capacity [4]. Previous researches focus on

studying the effect of replacing natural fine aggregate by fine PET plastic waste aggregate in

concrete.

The influence of polyethylene terephthalate (PET) bottles waste plastic lightweight aggregate on

the workability, density, compressive strength, splitting tensile strength, flexural strength and

modulus of elasticity of concrete was investigated by Choi et al. [5]. Water-cement ratios were in

the proportions of 45%, 49% and 53% and the replacement ratios of plastic waste were 25%, 50%

and 75% by volume to natural fine aggregate. The results show that the incorporation of PET

plastic waste aggregate in concrete increases slump value with the increase in water/cement ratio

and the replacement ratio of PET plastic waste. It was found that the compressive, splitting tensile

and flexural strengths of concrete mixtures decrease with the increase of PET plastic waste

aggregate content.

Rahmani et al. [6] studied the mechanical properties of concrete containing PET plastic waste

particles of 5%, 10% and 15% as a substitution by volume of sand. The properties investigated

were, workability, fresh density, dry density, compressive strength, splitting tensile strength,

modulus of elasticity, flexural strength and ultrasonic pulse velocity. It was demonstrated that, as

the content of PET plastic waste aggregate increases, the workability, compressive strength,

splitting tensile strength and modulus of elasticity are decrease.

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March 2017

II. RESERCH SIGNIFICANT

There is no detail study on properties of concrete with coarse PET plastic waste aggregate as a

replacement to natural coarse aggregate. The main objective of this study is to offer an attractive

low-cost concrete with sufficient properties and improves the sustainability in concrete industry by

using PET waste as a replacement to coarse aggregate in concrete instead of using it as a

replacement to fine aggregate. This will reduce the cost of grinding of the plastic waste to fine

particles. Also the use of silica fume as a by-product supplementary cementitious material in

concrete to replace a portion of cement weight has many benefits such as, decreasing the usage of

natural resources, wastes consumption, avoiding the environmental pollution and economizing

energy.

III. EXPERIMENTAL WORK

Materials Ordinary Portland cement Type (I) manufactured in Iraq with trade mark of (Al-Mass) was used.

The chemical composition and physical properties of cement used throughout this research indicate

that the adopted cement satisfies the requirements of the Iraqi Specifications No.5/1984. Natural

sand with maximum aggregate size of 4.75mm was used. The grading of fine aggregate lies in zone

(2). The test results show that sand grading; physical properties, and sulphate content conform the

requirements of the Iraqi Specifications No.45/1984. Natural crushed aggregate brought from AL–

Badrah region was used in this investigation. It has a maximum particle size of 10 mm. The grading,

sulphate content, and other properties of the coarse aggregate conform to the requirements of Iraqi

Specifications No. 45/1980. Coarse PET plastic waste aggregate was prepared by grinding waste

PET plastic bottles. The preparation process of PET plastic waste aggregate consist of many steps,

collecting the PET bottles wastes, removing the cover and trade label, washing and drying the

bottles, shredding and grinding the PET bottles to the specified particles size as that of natural

coarse aggregate used in concrete by plastic granulator machine (blade mill). The grinding process

was carried out in the Bob Al-Shaam area in Baghdad, and finally the grinded PET plastic waste

were screened on standard sieves and prepared with grading which conforms the grading of natural

coarse aggregate used in this investigation.

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March 2017

Table (1) shows the grading of PET plastic waste aggregate. Table (2) illustrated the physical

properties of PET plastic waste aggregate, while Figure (2) shows samples of natural aggregate and

PET plastic waste aggregate used in this investigation. The water used for mixing and curing of

concrete was potable water from the water-supply network system (tap water). Chemical and

mineral admixtures were used in this research as follows:

A high range water reducing admixture (superplasticizer) with a trade name GLENIUM 54 was

used [7]. According to the manufacturer the recommended dosage is between 0.5 and 2.5 liters per

100 kg of the cementitious material. This admixture is free from chlorides and complies with

ASTM C494 type F. Silica fume is a highly active pozzolanic material. It is a by-product from the

manufacture of silicon or ferro-silicon metal. Silica fume used throughout this investigation is

commercially known as MEYCO MS 610 from the chemical company BASF as partial

replacement of cement weight. The physical and chemical properties of silica fume used in this

investigation satisfy the requirements of ASTM C1240.

Concrete Mixes Six concrete mixes were prepared in this study including, concrete mix with natural aggregate

(reference mix) and five concrete mixes containing different volumetric replacement of coarse

natural aggregate (10%, 20%, 30%, 40% and 50%) by coarse PET plastic waste aggregate.

Table (1) Sieve analysis of PET plastic waste aggregate

Table (2) Physical properties of PET plastic waste aggregate

Physical properties Results*

Specific gravity 1.34 Water absorption (24 hr) 0.00%

Thickness 0.15mm- 1mm

Shape of particles Flaky and shredded particles and some pellets

pieces with maximum size of 12 mm

Color Crystalline white to blue sky

*Carried out in the laboratory of the Building and Construction Engineering Department/ University of Technology

Sieve size (mm) % Passing Limits of Iraqi specification No.

45/1981984 with single size (10mm)

14 100 100

9.5 94 85-100

4.75 23 0-25

2.36 0 0-5

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March 2017

(a) Natural coarse aggregate (b) PET plastic waste coarse aggregate

Figure (2) Types of coarse aggregate used in this investigation

Mixing of Concrete and Preparation of Specimens The mixing process was performed in an electrical rotary mixer of 0.1m3 capacity. The coarse and

fine aggregate were wetted to be in a saturated surface dry condition and mixed for one minutes.

Cement and silica fume were mixed by hand for two minutes, then two-thirds of mixing water was

added to the dry mixture and mixed for one minute. The superplascizer was mixed with the

remaining third amount of mixing water, then added to the mixture and the mixing process was

continued for two minutes. The steel moulds were well cleaned and their internal surfaces were

oiled to prevent adhesion with concrete after hardening. The moulds were filled with concrete in

layers (50 mm depth) and each layer was compacted by a vibrating table for about 20 seconds

which is a sufficient period to remove any entrapped air. After compaction, the specimens were

levelled by hand troweling, covered with polyethylene sheet and left in the laboratory. After 24

hours the specimens were demolded, marked and then cured. Then all specimens were completely

immersed in water until the time of testing at 28 days age.

Experimental Tests

A number of experimental tests were carried out to study some properties of sustainable concrete

containing PET plastic waste aggregate. These tests including, slump test according to ASTM C-

143, fresh density test according to ASTM C 138M, oven dry density test according to ASTM

C642, water absorption test according to ASTM C642, ultrasonic pulse velocity test according to

ASTM C597, compressive strength test according to B.S. 1881 (using cubes of 100 mm), splitting

tensile strength test according to ASTM C496–07 (using cylinders of 100×200 mm), flexural

tensile strength test according to ASTM C78-02 (using 100×100×400 mm prisms), and static

modulus of elasticity test according to ASTM C469-02 (using cylinders of 150×300 mm).

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March 2017

IV. EXPERIMENTAL RESULTS

Selection of Mix Proportions of Sustainable Concrete

Concrete mix with minimum compressive strength of 40 MPa at 28 days without any admixtures

was designed in accordance with ACI 211.1 [8]. The mix proportion is 1:1.19:1.8 (cement: sand:

gravel) by weight, with cement content of 525 kg/m3, w/c ratio of 0.41, and slump value of 90±5

mm. The optimum dosages of superplasticizer and silica fume were selected after the preparation of

many trial mixes. The workability of these trial mixes was similar to that of concrete mix without

any admixtures (slump of 90±5 mm) by adjusting the water to cement ratio. The main function of

using superplasticizer is to reduce the quantity of mixing water while maintaining the same

workability of the reference mix. The details of the designed reference concrete mix containing

different dosages of superplasticizer (HRWRA) are given in Table (3). According to the

manufacturer the normal dosage of HRWRA is between 0.5 and 2.5 liters per 100kg of cement or

cementitious material. The experimental results in this investigation indicate that the optimum

dosage of HRWRA is 1.5 liters per 100 kg of cement which leads to a water reduction of about 44%

and maximum compressive strength of 84 MPa at age 28 days. A significant attention has been

given to the use of silica fume in concrete mixtures. Silica fume was used as an addition or as a

partial replacement to cement, or both. It is suggested that silica fume can be added in addition to

existing cement in very highly aggressive environments, in order to substantially increases the

chemical resistance and durability of the concrete [9,10]. In this investigation, different dosages of

silica fume were used as a replacement to cement weight including, 5%, 10%, and 15%. The results

listed in Table (4) show that the compressive strength increases with the increase of silica fume

dosage. This is due to the physical and chemical effect of silica fume. The results indicate that the

maximum compressive strength obtained is 110.4 MPa at 28 days age for concrete mixture

containing 15 % of silica fume as a replacement to cement weight.

Workability

The relationship between the workability and the volumetric replacement of PET plastic waste

aggregate is illustrated in Figure (3). It can be observed that as the content of PET plastic waste

aggregate increases to 30, 40% and 50% as volumetric replacement to natural coarse aggregate, the

slump value increases by about 4.4%, 6.66% and 7.77% respectively compared with the reference

The First International Conference for Engineering Researches

March 2017

concrete. This is due to the smooth surface texture and low water absorption of PET plastic waste

particles.

Fresh Density

The fresh density of reference concrete mix and sustainable concrete mixtures containing various

contents of plastic waste aggregate are presented in Table (5). The results show that there is a

decrease in the fresh density as the PET plastic waste aggregates content increases. The percentage

reduction in fresh density for concrete containing 50% PET plastic waste aggregate as a volumetric

substitution to natural coarse aggregate is about 19.16% in comparison with the reference concrete.

This is due to the lower density of the PET plastic waste compared with natural coarse aggregate.

The same results were observed by Saikia and De Brito [11].

Table (3) Details of trail mixes for various dosages of HRWRA

Table (4) Details of trial mixes for various dosages of silica fume as a replacement by weight of cement

Mix

p

rop

orti

ons

by

wei

ght

Dos

age

of

HR

WR

A

(lit

er/1

00k

g of

cem

ent)

w/c

rat

io

S

lum

p

(mm

)

Wat

er

red

uct

ion

(%

) Compressive

strength (MPa) 14

d

ays

28

day

s

1: 1

.19:

1.8

C

emen

t:

San

d:

Agg

reg

ate

0 0.41 95 - 26.4 35.06

0.5 0.30 90 26.8 50.6 60.5

1 0.25 93 39 57.8 76.6

1.5 0.23 95 43.9 69.8 84.2

1.7 0.22 95 46.3 58.4 76.5

M

ix p

rop

orti

ons

by

wei

ght

Dos

age

of H

RW

RA

(l

iter

/100

kg

of c

emen

t)

Sil

ica

fu

me

as a

re

pla

cem

ent

by

wei

ght

of c

emen

t

w/c

rat

io

S

lum

p (

mm

)

Compressive strength (MPa)

14 d

ays

28 d

ays

1:1.

19:1

.8

Cem

ent:

S

and

: A

ggre

gat

e

1.5 0

0.23 95 69.8 84.2

1.5 5 0.20 92 73.8 90.0

1.5 10 0.22 93 85.2 92.5

1.5 15 0.23 90 84.0 110.4

The First International Conference for Engineering Researches

March 2017

Figure (3) Effect of PET plastic waste content on the workability of sustainable concrete

Oven Dry Density

The dry density of concrete containing coarse PET plastic waste aggregate decreases as the content

of PET plastic waste aggregate is increased, as shown in Table (5). This is due to the angular shape

of plastic particles, which contributes to the formation of large cavities in concrete, also due to the

low specific gravity of PET plastic waste compared with the natural coarse aggregate. Concrete

containing 40% and 50% PET plastic waste as volumetric replacement to natural coarse aggregate

has dry density of 1910 and 1850 kg/m3 respectively. These concretes are classified as lightweight

concretes according to ACI 213R [12].

Water Absorption

The results indicate that, as the content of PET plastic waste aggregate increases the water

absorption of concrete is increased, as shown in Table (5). This is because the inclusion of plastic

waste aggregate increases the porosity of concrete since the shape of PET plastics waste is angular.

Generally, the water absorption for all concrete specimens is less than 10 percent by weight. This

shows the good quality of all concrete mixes containing PET plastic waste as coarse aggregate [1].

Compressive Strength

The effect of PET plastic waste aggregate content as volume replacement to natural coarse

aggregate on the compressive strength of concrete is illustrated in Table (5). The results indicate

that the compressive strength decreases with the increase of PET plastic waste aggregate content.

The percentages reduction in compressive strength for concrete containing 10%, 20%, 30% 40%,

and 50% PET plastic waste as volumetric replacement to natural coarse aggregate are 33%,

41.39%, 68.47%, 69.61% and 84.4% respectively compared with the reference specimens. The

889092949698

0 10 20 30 40 50 60

Slu

mp

(m

m)

Percentage of PET plastic waste aggregate by volume

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March 2017

compressive strength is between 17.15 MPa and 73.9 MPa for concrete specimens with PET plastic

waste aggregate. The results of dry density and compressive strength for concrete specimens with

40% and 50% PET plastic waste aggregate indicate that this concrete can be classified as structural

lightweight concrete according to ACI 213R [12]. The reduction in compressive strength is

attributed to the reduction in adhesive strength between the surface of PET plastics and the cement

paste. Also it is due to the mismatch of particles size and shape between natural and plastic waste

aggregate [11].

Ultrasonic Pulse Velocity (UPV)

The test results in Table (5) show a reduction in ultrasonic pulse velocity with the increase of PET

particles content in the mixture. This is due to the fact that substituting natural coarse aggregate by

PET particles makes concrete structure more porous. The cavities formed attenuate the ultrasonic

wave due to the acoustic impedance [6, 13].

Splitting Tensile Strength

The results of splitting tensile strength at 28 days age of reference specimens (without plastic

aggregate) and concrete specimens with different contents of PET plastic waste aggregate are

presented in Table (6). It can be noted that there is a slight reduction in splitting tensile strength of

about 10.4%, for concrete specimens containing 10% PET plastic waste aggregate relative to the

reference specimens without PET plastic waste aggregate. As the content of PET plastic waste

aggregate increases, the splitting tensile strength is significantly decreased. The percentage

reduction is 29.6%, 45.6%, 63.2% and 70.7% for concrete specimens containing 20%, 30%, 40%

and 50% PET plastic waste aggregate as a volumetric substitution to natural coarse aggregate

respectively. This is because of the weak cohesion between the cement paste and the PET particles.

The smooth surface of the plastic particles may causes weak bond strength between PET plastic

and the cement matrix [14].

Flexural Strength

The results of the flexural strength tests for all concrete specimens prepared in this investigation are

illustrated in Table (6). A slight decrease is observed for concrete specimens with low content (10%

and 20%) of PET plastic waste aggregate in comparison with the reference concrete specimens.

However a significant decrease of 31.5%, 42.05% and 43.5% is observed for concrete specimens

containing 30%, 40% and 50% PET plastic waste aggregate respectively. This is due to the

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March 2017

formation of more voids with the high contents of PET plastic waste and the low bonding strength

between the cement matrix and plastic waste particles [14].

Static Modulus of Elasticity

Table (6) shows that, the value of modulus of elasticity decreases with the increase of PET coarse

plastic waste aggregate content. Concrete specimens with low content of plastic waste (10% and

20%) show slight reduction in modulus of elasticity, while there is a significant reduction in the

modulus of elasticity for concrete specimens with 30%, 40% and 50% coarse PET plastic waste

aggregate. The decrease in modulus of elasticity is due to the low modulus of elasticity for PET

plastic particles compared with the natural coarse aggregate. The low bond strength between the

cement paste (matrix) and plastic aggregates can also contribute to this drop [15].

Table (5) Some properties of PET plastic waste aggregate concrete

M

ix s

ymb

ol

PE

T p

last

ic w

aste

(%

) b

y vo

lum

e of

nat

ura

l co

arse

ag

greg

ate

Fre

sh d

ensi

ty (

kg/

m3)

Dry

den

sity

(k

g/m

3)

Per

cen

tage

of

wat

er

abso

rpti

on

UP

V (

km

/sec

)

Com

pre

ssiv

e s

tren

gth

at

28 d

ays

(MP

a)

Per

cen

tage

red

uct

ion

i

n c

omp

ress

ive

st

ren

gth

Reference R 0 2530 2418 1.12 6.8

110.4

-

Con

cret

e co

nta

inin

g P

ET

pla

stic

w

aste

ag

gre

gate

C- PET10

10 2435 2335 2.6 5.95 73.9 33.06

C- PET20 20 2380 2290 3.2 5.5 64.7 41.39

C- PET30 30 2260 2120 3.9 4.58 34.8 68.47

C- PET40 40 2105 1910 5.8 3.9 23.0 79.61

C- PET50 50 2045

1850

6.3 2.6 17.15 84.4

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Table (6) Effect of PET plastic waste aggregate content on some mechanical properties of concrete

V. CONCLUSIONS

The main conclusions that can be drawn from this investigation are:

1- The dry density of concrete containing coarse PET plastic waste aggregate decreases as the

content of PET plastic waste aggregate is increased. Concrete containing 40% and 50% PET

plastic waste as volume substitution to natural coarse aggregate has dry density of 1910 and

1850 kg/m3 respectively. This concrete can be classified as lightweight concrete.

2- The increase of plastic waste content in concrete increases the water absorption of concrete.

3-The compressive strength, splitting tensile strength, flexural strength, and static modulus of

elasticity of concrete decrease as the content of PET particles increased. The percentage

reduction in compressive strength, splitting tensile strength, flexural strength and static modulus

of elasticity for concrete specimens containing 50% coarse PET plastic waste aggregate by

volume is 84.4%, 70.7%, 43.4,% and 80.45% respectively compared with the reference

specimens.

M

ix s

ymb

ol

PE

T p

last

ic w

aste

(%

) b

y vo

lum

e of

nat

ura

l co

arse

ag

greg

ate

Cu

be

com

pre

ssiv

e st

ren

gth

at

28 d

ays

( M

Pa)

Sp

litt

ing

ten

sile

str

engt

h a

t 28

da

ys (

MP

a)

Red

uct

ion

in

sp

litt

ing

ten

sile

str

engt

h (

%)

F

lexu

ral

ten

sile

str

engt

h

at 2

8 d

ays

(MP

a)

Red

uct

ion

in

f f

lexu

ral

stre

ngt

h (

%)

S

tati

c m

odu

lus

of e

last

icit

y

at 2

8 d

ays

(GP

a)

Per

cen

tage

red

uct

ion

in

st

atic

m

odu

lus

of e

last

icit

y

Reference R 0 110.4

6.25

- 7.8

- 52.7 -

Con

cret

e co

nta

inin

g P

ET

pla

stic

w

aste

ag

gre

gate

C- PET10

10 73.9 5.6 10.4 7.3 6.4 47.7 9.4

C- PET20 20 64.7 4.4 29.6 6.24 20 46.8 11.2

C- PET30 30 34.8 3.4 45.6 5.34 31.5 34.9 33.7

C- PET40 40 23.0 2.3 63.2 4.52 42.05 22.8 56.7

C- PET50 50 17.15 1.83 70.7 4.4 43.5 10.3 80.4

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[4] Siddique, R., Khatib, J., and Kaur, I., "Use of Recycled Plastic in Concrete: a Review", International Journal of Civil, Structural, Environmental and Infrastructure Engineering Research and Development, Vol.3, No.2, pp. 9-16, 2013.

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[8] ACI Committee 211.1, “Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete”, 2004. [9] Mazloom, M., Ramezaniapour, J.J., and Brooks, J.J., “Effect of Silica Fume on Mechanical Properties of High-Strength Concrete”, Cement and

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