Effect of impact load in 12 story building

8/13/2019 Effect of impact load in 12 story building

1/17

Review

Use of plastic waste as aggregate in cement mortar and concrete

preparation: A review

Nabajyoti Saikia a,1, Jorge de Brito b,

a Department of Civil Engineering, Architecture and Georesources, Instituto Superior Tcnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon, Portugalb ICIST Research Institute, Instituto Superior Tcnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal

a r t i c l e i n f o

Article history:

Received 12 October 2011

Received in revised form 21 January 2012

Accepted 25 February 2012

Available online 5 April 2012

Keywords:

Plastic waste

Aggregate

Concrete

Cement mortar

Mechanical property

Durability

a b s t r a c t

A substantial growth in the consumption of plastic is observed all over the world in recent years, which

has led to huge quantities of plastic-related waste. Recycling of plastic waste to produce new materials

like concrete or mortar appears as one of the best solution for disposing of plastic waste, due to its eco-

nomic and ecological advantages. Several works have been performed or are under way to evaluate the

properties of cement-composites containing various types of plastic waste as aggregate, filler or fibre.

This paper presents a review on the recycling plastic waste as aggregate in cement mortar and concrete

productions.

For better presentation, the paper is divided into four different sections along with introduction and

conclusion sections. In the first section, types of plastics and types of methods used to prepare plastic

aggregate as well as the methods of evaluation of various properties of aggregate and concrete were

briefly discussed. In the next two sections, the properties of plastic aggregates and the various fresh

and hardened concrete properties of cement mortar and concrete in presence of plastic aggregate are

discussed. The fourth section focus on the practical implications of the use of plastic waste in concrete

production and future research needs.

2012 Elsevier Ltd. All rights reserved.

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386

2. A look on the materials and method sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386

2.1. Preparation of plastic aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386

2.2. Evaluation of properties of plastic aggregate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

2.3. Types and amount of substitution of natural aggregate by plastic aggregate in cement mortar/concrete mixes. . . . . . . . . . . . . . . . . . . . 387

2.4. Preparation and curing of cement mortar/concrete using plastic aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

2.5. Evaluated properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

3. Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

3.1. Properties of plastic aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

3.2. Fresh concrete properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389

3.2.1. Slump value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389

3.2.2. Unit weight/fresh density/dry density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390

3.2.3. Air content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391

3.3. Hardened concrete properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391

3.3.1. Compressive strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391

3.3.2. Splitting tensile strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392

3.3.3. Modulus of elasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393

3.3.4. Flexural strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394

3.3.5. Toughness/Poisons ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395

3.3.6. Failure characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396

3.3.7. Abrasion resistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396

0950-0618/$ - see front matter 2012 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.conbuildmat.2012.02.066

Corresponding author. Tel.: +351 218419709; fax: +351 218497650.

E-mail addresses: [email protected](N. Saikia), [email protected](J. de Brito).1 Tel.: +351 218418372; fax: +351 218497650.

Construction and Building Materials 34 (2012) 385401

Contents lists available atSciVerse ScienceDirect

Construction and Building Materials

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c o n b u i l d m a t
http://dx.doi.org/10.1016/j.conbuildmat.2012.02.066mailto:[email protected]:[email protected]://dx.doi.org/10.1016/j.conbuildmat.2012.02.066http://www.sciencedirect.com/science/journal/09500618http://www.elsevier.com/locate/conbuildmathttp://www.elsevier.com/locate/conbuildmathttp://www.sciencedirect.com/science/journal/09500618http://dx.doi.org/10.1016/j.conbuildmat.2012.02.066mailto:[email protected]:[email protected]://dx.doi.org/10.1016/j.conbuildmat.2012.02.066


2/17

3.4. Durability performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396

3.4.1. Permeability behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396

3.4.1.1. Water absorption and water accessible porosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397

3.4.1.2. Gas permeability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398

3.4.1.3. Chloride migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398

3.4.2. Carbonation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398

3.4.3. Shrinkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398

3.4.4. Freezing and thaw resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399

3.5. Other properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3993.5.1. Fire behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399

3.5.2. Thermo-physical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400

4. Practical implications of the results so far and future developments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400

5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401

1. Introduction

Plastic, oneof themost significant innovations of 20th century, is

a ubiquitous material. A substantial growth in the consumption of

plastic is observed all over the world in recent years, which also in-

creases the production of plastic-related waste. The plastic waste is

nowa seriousenvironmental threat to moderncivilisation. Plastic is

composed of several toxic chemicals, and therefore plastic pollutes

soil, air and water. Since plastic is a non-biodegradable material,

land-filling using plastic would mean preserving the harmful mate-

rial forever. The hazards that plastics pose are numerous. They may

block the drainage system of a city. The blocked drains provide

excellent breeding grounds for disease-causing mosquitoes and

water borne diseases besides causing flooding. Plastic garbage can

reduce therate of rainwater percolating anddeteriorate thesoil fer-

tility if it is mixed with soil. Plastic waste dumped into rivers,

streams and seas contaminates the water and marine life. Aquatic

animals can consume plastic waste, which can damage their health.

Some marinelifehas been found with plastic fragments in thestom-achs and plastic molecules in their muscles.

The Great Pacific Garbage Patch mainly consists of plastic

waste and it is believed to constitute 90% of all rubbish floating

in the oceans. The UN Environment Programme estimated in

2006 that every square mile of ocean contains 46,000 pieces of

floating plastic. More than one million sea birds and approximately

100,000 sea mammals die each year after ingesting or becoming

entangled in plastic debris. The threat of plastic waste seems to

be ever increasing. Many countries have restricted the use of plas-

tic bags and many are in the process of doing so.

Land-filling of plastic is also dangerous due to its slow degrada-

tion rate and bulky nature. The waste mass may hinder the ground

water flow and can also block the movement of roots. Plastic waste

also contains various toxic elements especially cadmium and lead,which can mix with rain water and pollute soil and water.

Recycling plastics is a possible option. As plastic is an organic

hydrocarbon-based material, its high calorific value can be used

for incineration or in other high temperature processes. But, burn-

ingof plastics releases a variety of poisonous chemicals into the air,

including dioxins, one of the most toxic substances. Plastic waste

can also be used to produce new plastic based products after pro-

cessing. However it is not an economical process as the recycled

plastic degrades in quality and necessitates new plastic to make

the original product.

Although these alternatives are feasible except for land-filling,

recycling of plastic waste to produce new materials, such as ce-

ment composites, appears as one of the best solution for disposing

of plastic waste, due to its economic and ecological advantages. Avast work has already been done on the use of plastic waste such

as polyethylene terephthalate (PET) bottle[18], poly vinyl chlo-

ride (PVC) pipe [9], high density polyethylene (HDPE) [10], thermo-

setting plastics[11], shredded and recycled plastic waste[1214],

expanded polystyrene foam (EPS) [15,16], glass reinforced plastic

(GRP) [17], polycarbonate [18], polyurethane foam [19,20], poly-

propylene fibre[21]as an aggregate, a filler or a fibre in the prep-

aration of concrete.

A review on the use of plastic waste in preparation of cement

mortar and concrete preparation is already available [22]. How-

ever, several important properties such as toughness, failure

characteristics, thermo-physical properties, durability perfor-

mance of cement mortar and concrete containing plastic as

aggregate were not discussed before due to lack of available

information. Data were provided only for some of properties,

where plastic was used as fibre in concrete and therefore the

amount incorporated was very low in comparison to its use as

aggregate or filler. Moreover, information that appeared in sev-

eral works that have been published recently provided a clearer

picture on the properties of concrete containing plastic as aggre-gate, filler or fibre (granular additive) in the preparation of ce-

ment mortar and concrete and therefore, from the authors

point of view, a new review is needed to look at the latest devel-

opment on the evaluation of this material as granular additives

in the preparation of cement-based mixes. Therefore, in this pa-

per, a thorough review on the use of plastic waste as a partial or

full replacement of natural aggregate in cement mortar or con-

crete preparation is presented. Several plastic wastes are also

used in the preparation of polymer concrete [22]. However in

this review, the behaviour of this type of materials is overlooked

due to size limitations of the manuscript. For a better presenta-

tion, the paper is divided into four different sections along with

the introduction and conclusion sections.

2. A look on the materials and method sections

2.1. Preparation of plastic aggregates

The majority of plastic aggregates used in different studies were prepared from

plastic waste obtainedfrom different sources. In general plastic bottles weregrinded

inthe laboratory byusinga grindingmachineandthensieved toget the suitable size

fraction[6,9,23,24].Different types of crusher like propeller crushers or blade mills

areusedto grindthe plastic waste. Howeverin some studies, plastic wastewithsuit-

ablesizes wascollected fromplasticwaste treatment plants or plastic manufacturing

plants [1,13,25]. In this case, sieving into suitable size range was done at thelabora-

tory[1820,25]. In some studies a washing stage is adopted to remove impurities

present in the plastic wastes[1,6,26].Separate grinding steps are also adopted after

normal shreddingto increase thecementpasteplastic aggregatebonding. Forexam-

ple, Remadnia et al. shredded plastic pieces in one more stage using a propeller

crusher in order to control size limit withcrushing and to facilitate matrix-aggregateadhesion due to the irregular shape androughsurface texture [26].

386 N. Saikia, J. de Brito / Construction and Building Materials 34 (2012) 385401


3/17

In plastic waste treatmentplants, several steps are adopted to recycle thewaste

plastic. Saikia and de Brito[27]reported the use of three types of plastic aggregate

(flaky waste PET aggregatewith two different size ranges and a pellet-shaped prod-

uct) directly collected from waste PET treatment plant as aggregate in concrete. The

two types of aggregates were obtained after mechanical grinding of PET waste. The

washing of waste PET was done before and after grinding by using alkaline solu-

tions. Stirring of ground PET in a clean water bath and centrifugation of grinded

PET waste were also done to remove impurities. Several impurities such as paper,

dust, PVC, ground glass and glues were removed during these treatment steps.

The grinding of PET waste generated flaky PET particles in the size range of 1014 mm with small amount of fine particles. These fine PET particles were removed

by using a de-dusting system. The pellet-shaped PET-waste fraction was produced

from coarse plastic flakes in a reactor according to predetermined conditions. The

heating and melting of the heated material is performed in such a way that allows

the extraction of volatile contaminants. The extrusion process is relatively short,

which limits the occurrence of secondary reactions during the melting stage. After

passing through a spinneret, themeltis collected in a cooling bath that solidifiesthe

polymer before being granulated in a rotary cutter in water. The mixture of water

and grains of polymer is subjected to a vibratory separator and then the grains of

polymer (plastic pellets) are centrifuged to remove excess water.

Modifications of plastic waste by heating, by mechanical means, by soaking in

water, melting followed by mixing with other materials and other techniques were

also done to improve the quality of plastic waste for using as aggregate in concrete

[3,4,15,16,28] . Choi et al. prepared two types of plastic aggregates by mixing gran-

ulated pet waste bottle with powdered river sand and blast furnace slag at 250 C

[3,4]. After air-cooling the mixtures, the prepared aggregates and remaining pow-

dered fractions were screened by using a 0.15 mm sieve. The schematic diagram

to produce a typical PET aggregate according to Choi et al. is presented in Fig. 1[3].

Kan and Demirboga prepared an aggregate from expanded polystyrene (EPS)

foams waste. This modified expanded polystyrene (MEPS) waste aggregates were

prepared by melting EPS foams waste in a hot air oven at 130 C for 15 min[15,16].

2.2. Evaluation of properties of plastic aggregate

The properties of plastic waste to be used as an aggregate in concrete prepara-

tions such as size distribution, bulk density, specific gravity, and water absorption

were generally evaluated in the majority of the reported studies. The evaluation of

size distribution of plastic aggregates was generally done by standard sieving meth-

ods [6,9,11,13,2325]. However, in some studies, slightly different approaches were

adopted[2,20].

From the authors experiments, it can be stated that the standard procedures

used to evaluate properties like bulk density, specific gravity, and water absorption

of coarse and fine natural aggregates can be used to evaluate these parameters inplastic aggregate with slight modifications [25]. On the other hand, some other

properties such as hardness (tensile and compressive strengths, elastic modulus)

of plastic aggregate, decomposition temperature, melting and initial degradation

temperatures and melt flow index (MFI), heat capacity, and thermal conductivity

were also reported.

2.3. Types and amount of substitution of natural aggregate by plastic aggregate in

cement mortar/concrete mixes

Plastic aggregates are generally produced from big sized plastic waste materi-

als. Therefore both coarse and fine sized natural aggregate can be replaced by plas-

tic aggregates. Both partial and full substitutions of natural aggregates by plastic

aggregates were reported in various references. In several studies, fine natural

aggregate of cement mortar and concrete was replaced by coarse sized aggregate

too [2,13]. Table 1 highlights the types and amounts of substitution of natural

aggregate by plastic aggregate in the preparation of cement mortar and concrete.

2.4. Preparation and curing of cement mortar/concrete using plastic aggregate

Generally, the design, preparation and casting of concrete mix containing plas-

tic aggregate are similar to the normal concrete/mortar mix design and done

according to various standard specifications. However, designing and/or curing of

some concrete mixes containing plastic aggregate were done by slightly different

approaches than for normal concrete mix design [2,6,13,15,20,28]. Some types of

plastic aggregatesuch as plastic foam canconsume water that is necessary forhard-

ening and therefore concrete specimens containing these types of plastic aggregate

at certain replacement amount cannot be completely hardened after 24 h of normal

curing before demoulding the specimens [19].

2.5. Evaluated properties

The slump and density/unit weight of fresh concrete and different strength

properties and elasticity modulus of hardened concrete are normally evaluated

along with some durability properties and some other special properties like fire

behaviour, thermal insulation properties, microstructure and reactivity of plastic

in alkaline solution (Tables 2 and 3). The evaluation of properties was done using

the normal procedures adopted for conventional concrete and mortar.

3. Results

3.1. Properties of plastic aggregates

As the chemical nature of plastic aggregate is completely differ-ent from that of natural aggregate i.e. one is organic and the other

is inorganic and therefore a big difference in aggregate properties

Fig. 1. Manufacturing process of sand coated PET aggregate [3].

N. Saikia, J. de Brito / Construction and Building Materials 34 (2012) 385401 387


4/17

is generally observed. The properties of some types of plastic used

as an aggregate in concrete are presented in Table 4.

The use of polyethylene terephthalate (PET) as aggregate was

studied extensively compared to other types of plastic aggregates.

Table 1

Types of substitution of natural aggregate by plastic aggregate in cement mortar/concrete.

Reference Types of composite Types and amounts of substitution Origin of plastic waste

[2] Concrete Fine aggregate 10 and 20 vol.% PET-bottle

[24] Concrete Fine aggregate 5, 10, 15, 20 vol.%

[13] Concrete Fine aggregate 10, 15, 20 wt.% Plastic containers (80% polyethylene and 20% polystyrene)

[9] Light-weight aggregate

concrete

Fine aggregate 5, 15, 30, 45vol.% PVC pipe

[6] Mortar Fine aggregate 2, 5, 10, 15, 20, 30, 50, 70,100 vol.%

PET-bottle

[11] Non-load-bearing lightweight

concrete

With sand fraction in aerated concrete Melamine waste

[19] Concrete Coarse aggregate 34, 35, 45 v ol.% of

concrete

Waste polyurethane foamcollected after destruction of insulation panels used

in building industry

[23] Concrete Fine aggregate 5 wt.% PET-bottle

[26] Mortar Fine aggregate 30, 50, 70 vol.% PET-bottle

[18] Mortar Fine aggregate 3, 10, 20, 50vol.% A mixture of polyethylene terephthalate (PET) and polycarbonate Industrial

waste

[15] Concrete Fine and coarse aggregate 25, 50, 75,

100 vol.%

Waste packaging materials composed of expanded polystyrene foams

[20] Mortar With fine aggregate 13.133.7 v ol.% of

concrete

Waste polyurethane foamcollected after destruction of insulation panels used

in building industry

[1] Mortar With fine aggregate 50 and 100 wt.% PET-bottle

[3,4] Mortar and concrete With fine aggregate 25, 50, 75, 100 vol.% PET-bottle

Table 2

Fresh and hardened mechanical properties of concrete reported in the literature.

Reference Slump Density Compressive strength Tensile strength Flexural strength Elasticity modulus SS curve Pulse velocity

Fresh Dry

[2] p p p p p p

[23] p p p

[13] p p p p p

(Toughness)

[6] p p p p

[9] p p p p p p

(Poisons ratio)

[24] p p p p p

[11] p p

[1] p p p p

[15] p p p p p p

[20] p p p p

[27] p p p p [3,4] p p p p p

[19] p p p p p

[26] p p p p

[18] p p p p

(Toughness)

Table 3

Durability-related and other properties of concrete reported in the literature.

References Shrinkage Water

absorption

Water

sorptivity

Gas

permeability

Carbonation Cl

migration

Fire

behaviour

AEa Microstructure Thermal

properties

Freezethaw

resistance

[2] p p p

[23] p

[6] p

(Steam

water)

p p

[9] p p

[1] p p(Porosity) p[15]

p[20]

p(Mass

loss)

p

[19] p p p p p

[26] p p

[18] p

(Porosity)

p p

[3,4] p

[27] p p

a AE: activation energy.



5/17

The PET has very low thermal conductivity (0.130.15

0.24 W m1 K1) compared to two common concrete aggregate,limestone (1.261.33 W m1 K1) and sandstone (1.7 W m1 K1).Again the specific heat capacity of PET (1.01.1 kJ kg1 K1) is high-er than those of limestone (0.84 kJ kg1 K1) and sandstone(0.92 kJ kg1 K1).

PET consists of polymerised units of the monomer ethylene

terephthalate with repeating C10H8O4 units and therefore the

molecular formula of PET can be represented as (C10H8O4)n. The

molecular structure of PET is presented in Fig. 2.

Highly alkaline concrete pore fluid can degrade PET [7]. The ions

present in pore fluid, Ca

2+

, Na

+

, K

+

, and OH can attack the CObonds of PET and split the polymer into two groups: the group of

the aromatic ring and the group of aliphatic ester. The alkali ions

can interact with aromatic rings and form Ca, Na, and K-terephtha-

lates. On the other hand, hydroxyl ion can form ethylene glycol by

reacting with the aliphatic ester group.

3.2. Fresh concrete properties

3.2.1. Slump value

The slump is used to measure the workability or consistency of

fresh concrete mix. Being an important property, the slump of con-

crete and cement mortar mix containing plastic aggregate was

studied extensively. Some typical results observed in various stud-ies are presented inFig. 3.

Table 4

Properties of some types of plastic used as an aggregate in concrete.

Reference Type of plastic Particle size/shape Density/specific gravity/apparent

bulk density#Water

absorption

Other properties

[2] PET 0.26 and 1.14 cm (average

size of two fractions)

MP: 248 C

Initial degradation temperature:

412 C MFI: 70g/10 min

[24] Plastic waste 0.154.75 mm [13] 80%

polyethylene + 20%

polystyrene

Length: 0.1512 mm #386.7 kg/m3 0.02% CS: poor

Width: 0.154 mm/Flakes TS: 5000 psi

[6] PET Type A: 60.5 cm Type A: #326 kg/m3

Type C: 60.2 cm Type C: #345 kg/m3

Type D: 60.1 cm Type D: #408 kg/m3

[26] PET 64 mm/thin #327 kg/m3 0 TS: 75 MPa

MP: 249271 C

TC: 0.13 W/mK

MHC: 1.11.3 kJ/kg K

[1] PET 0.254 mm 1.27g/cm3

[18] PET 1.610 mm #547 kg/m3/1.36 Colour: white

MP: 255

YM: 17002510 MPa

[18] PC 65 mm #646 kg/m3/1.24 Colour: transparent

MP: 230250YM: 2700 MPa

[4] PET (coated with slag) Round and smooth 1.39 g/m3/#844kg/m3 0 FM: 4.11

[3] PET (coated with sand) 0.154.75 mm/round and

smooth

1.39 g/m3/#844kg/m3 FM: 4.11

[23] PET Thickness: 11.5 mm

Size: 0.15 mm

[9] PVC 65 mm/granular 1400 kg/m3/#546 kg/m3 CS: 65 MPa

[11] Melamine waste


6/17

There are two parallel views on the workability behaviour of

concrete containing plastic aggregate. In the majority of the stud-

ies, a lower slump value of fresh concrete due to the incorporation

of several types of plastic aggregates than that of the conventional

concrete mix was observed and an increasing addition of plastic

aggregate further lowers the slump value [2,9,13,23,24]. The rea-

sons for the lower slump value of the concrete mix containing plas-

tic aggregate are the sharp edges and angular particle size of plastic

aggregate.

On the other hand, in a few studies, an increase in the slump va-

lue due to the incorporation of plastic aggregate is also reported

[3,4,12], the increase of the slump of concrete mixes due to the

incorporation of plastic aggregates is due to the presence of more

free water in the mixes containing plastic than in the concrete

mix containing natural aggregate since, unlike natural aggregate,

plastic aggregates cannot absorb water during mixing [12]. Choi

et al. reported an increase in the slump value of concrete with

increasing content of two types of treated PET-bottle aggregate

in concrete (Fig. 4)[3,4]. The aggregates were spherical in shape.

According to the author, this trend is due to the spherical shape

of the PET aggregate as well as the slippery surface texture, which

decreases the inner friction between the mortar and the PET aggre-

gate and therefore increases the slump value.

Saikia and de Brito found two types of workability behaviour in

concrete mixes containing two differently shaped PET aggregates

[25]. In this work, a pellet-shaped PET aggregate with very smooth

surface texture and two different size fractions of a flaky PET

aggregate were used to partially replace coarse and fine sized nat-

ural aggregates. All the PET aggregates were obtained from the

same type of plastic waste materials.

To achieve a constant slump value, the concrete mix containing

pellet plastic aggregate required a slightly lower w/c value and the

concrete mixes containing the two flaky plastic aggregates with

different particle size required much higher w/c values than that

required by the concrete mix containing natural aggregate. On

the other hand, a substantially higher w/c value was obtained for

the concrete mix containing coarse flaky PET aggregate than thatobserved for the concrete mix containing fine flaky PET aggregate.

This clearly indicated that the addition of pellet PET aggregate in-

creased the slump value of the resulting concrete mix, due to its

spherical nature and smooth surface texture. On the other hand,

the decreasing slump values due to the addition of fine and coarse

flaky plastic aggregates are attributed to the fact that these PET

aggregates have sharper edges compared to natural aggregate

(NA). Moreover in comparison to NA, these flaky aggregates are

angular and non-uniform in nature.

The addition of some types of plastic aggregate such as rigid

polyurethane foam waste or heat-treated expanded polystyrene

foam (MEPS) decrease the slump value of the resulting concrete

mix due to the presence of large amounts of surface pores in these

aggregates[15,19,20]. The slump values of various concrete mixes

containing modified expanded polystyrene foam aggregate is pre-

sented inTable 5.

3.2.2. Unit weight/fresh density/dry density

Irrespective of the type and size of substitutions, the incorpora-

tion of plastic as aggregate generally decreases fresh and dry den-

sities of the resulting concrete due to the lightweight nature of

plastic aggregate[3,4,6,9,12,13,18,25]. Some results are presented

inFig. 5.

Ismail and Al-Hashmi reported the fresh density of concrete

containing plastic as fine aggregate [13]. Their results indicated

that the fresh density of concrete containing 10%, 15%, and 20%

plastic aggregate as a replacement of fine aggregate tends to de-

crease by 5%, 7%, and 8.7% respectively, below the reference con-

crete. Al-Manaseer and Dalal also found 2.5%, 6% and 13% lower

densities of concrete mix containing 10%, 30%, and 50% plastic

aggregates respectively[12].

Saikia and de Brito observed a reduction of the density of fresh

concrete with increasing volume of embedded PET aggregates [25].

The authors found a trend of this density reduction for three differ-

ent types of PET aggregates used in this investigation: pellet plastic

aggregate < fine fraction of flaky plastic aggregate < coarse fractionof flaky plastic aggregate.

Marzouk et al. reported the bulk density of cement mortar

mixes prepared by replacing 0100% in volume of sand by two dif-

ferent sizes of PET aggregates [6]. Their results showed that the

reduction of bulk density remained small when the volume occu-

pied by aggregates varies between 0% and 30%, regardless of their

size. However, when this volume exceeded 50%, the composite

bulk densities started to decrease until reaching a value 1000 kg/

m3. They also found that for the same volumetric percentage of

substitution the bulk density decreased with decreasing particle

size.

Fraj et al. observed a significant reduction in fresh density and

28-day air-dried density of concrete containing coarse rigid

Fig. 4. Improvement of workability due to the addition of slag coated PETaggregate, WPLA[4].

Table 5

Water/cement ratio and slump values of concrete containing modified expanded

polystyrene foam as aggregate[15].

MEPS/

NA

ratio

Fine fraction of MEPS/

coarse fraction of MEPS

Fine fraction of NA/

coarse fraction of NA

W/C

value

Slump

value

100/0 50/50 0.38 25

75/25 25/50 25/0 0.39 30

50/50 0/50 50/0 0.42 3050/50 50/0 0/50 0.42 30

50/50 25/25 25/25 0.42 40

25/75 25/0 25/50 0.43 50

1.5

1.7

1.9

2.1

2.3

2.5

0 10 20 30 40 50

Density(103)(Kg/m3)

Substitution amount (%)

[A]

[B]

[C] coarse

[C] fine

[C] pellet

Fig. 5. Fresh density of concrete due to the incorporation of various types of plasticaggregate: [A][13]; [B][9]; [C][25].



7/17

polyurethane (PUR) foam waste aggregate due to the lower density

of the PUR foam aggregates (Table 6) [19]. According to the

authors, the fresh densities of different concrete mixes containing

dry and water saturated PUR foam aggregate can be considered as

lightweight concrete and these values were 2733% lower than the

control concretes density. The density values decreased as foam

proportioning increased.

Hannawi et al. reported the fresh and dry densities of concrete

containing PET waste and polycarbonate (PC) waste as aggregate

[18]. Their results showed that there was a decrease in the fresh

and dry densities as the plastic aggregates content increased. The

dry density decreased from 2173 kg/m3 for mixes containing 0%

of plastic aggregates to 1755 and 1643 kg/m3, respectively, for

mixes containing 50% of PET and PC plastic aggregates. These val-

ues were lower than 2000 kg/m3, the minimum dry density re-

quired for structural lightweight concrete according to RILEM

LC2 classification. The 50% replacement of fine aggregate by PET

and PC reduced the dry density by upto 19% and 24% of that of nor-

mal concrete, respectively, which is mainly attributed to the lower

specific weight of the plastic.

3.2.3. Air content

No report is available on the evaluation of air-content of cement

mortar or concrete mixes containing untreated plastic waste as

aggregate. Choi et al. reported the air content of concrete contain-ing sand stone coated PET as partial replacement of fine aggregate

(Table 7)[3]. An air-entrainment agent was used during prepara-

tion of concrete. The air-contents of concrete mixes containing

PET aggregate were slightly lower than that of the control concrete

for the same w/c ratio and a reducing trend was observed with

increasing PET content in concrete.

3.3. Hardened concrete properties

3.3.1. Compressive strength

The compressive strength of concrete and cement mortar is a

fundamental property that is thoroughly studied in almost all re-

search works related to plastic aggregate. In all of these studies it

was found that the incorporation of plastic as aggregate decreased

the compressive strength of the resulting concrete/mortar [1

4,6,9,11,13,15,18,19,2326] .

Fig. 6 shows some of the reported results of 28-day compressive

strength performance of concrete containing plastic waste as par-

tial substitution of fine and coarse natural aggregates. The factors

that may be responsible for low compressive strength of concrete

containing plastic aggregate are: (1) the very low bond strength

between the surface of the plastic waste and the cement paste;

(2) the hydrophobic nature of plastic waste, which can inhibit ce-

ment hydration reaction by restricting water movement.

Albano et al. reported that concrete with 10% of recycled PET

exhibits a compressive strength that meets the standard strength

values for concrete with moderate strength (between 21 and

30 MPa for a curing age of 28 days)[2]. According to the authors,

the compressive strength at the age of 28 days is near the values

for 60 days. They recognised several factors such as the type of fail-

ure and the formation of honeycombs, low workability, particle

size, which are responsible for lower compressive strength of con-

crete containing PET aggregate than concrete containing natural

aggregate. The reduction in compressive strength was more pro-

nounced in concrete containing larger flaky PET aggregate than

smaller one. Saikia and de Brito [25] observed similar trends in

compressive strength for concrete containing fine and coarse flaky

PET aggregate, which was mainly due to the loss of workability ofthe concrete mix due to the shape of the PET aggregate, especially

for larger particles. The results obtained in both studies were pre-

sented inFig. 6.

Batayneh et al. also observed a reduction in the compressive

strength of concrete due to the addition of plastic waste as a partial

substitution of fine aggregate[24]. For 20% replacement compres-

sive strength shows a sharp reduction up to 72% of the original

strength and for 5% replacement the compressive strength drops

23%. Ismail and Al-Hashmi reported that the compressive strength

of concrete prepared by replacing 10%, 15% and 20% of fine natural

aggregate by PET aggregate are higher than the minimum com-

pressive strength required for structural concrete, which is

Table 6

Mix proportions and density values of the concrete mixes [19].

Mix code Mix proportions (kg/m3) PUR foam volume content (%) w/c ratio Density (kg/m3)

Cement Water Sand Normal aggregates PUR foam aggregates SP Fresh Dry

NWC 397 220 824 867 0 0.55 2327 LWAC-1 397 220 824 15.1 34 0.55 1791 1699

LWAC-1sat 397 220 824 15.1 34 0.55 1779 1679

LWAC-2sat 415 183 862 15.8 1.405 35 0.44 1776 1678

LWAC-3sat 353 156 734 20.1 1.196 45 0.44 1656 1538

Table 7

Air content of fresh concrete[3].

w/c Sand replaced by

PET aggregate (%)

Air content (%)

0.53 0 4.5

25 4.2

50 4.1

75 4.1

0.49 0 5.0

25 4.5

50 4.3

75 4.2

0.45 0 5.0

25 4.8

50 4.0

5

15

25

35

45

0 10 20 30 40

Compressivestrength(MPa)


Control [A]

Coarse [A]

Fine [A]

Control [B]

Coarse [B]

Fine [B]

[C]

[D]

Fig. 6. Compressive strength of concrete containing plastic aggregate: [A]: [25]; [B]:[2]; [C]:[24]; [D][9].



8/17

17.24 MPa, even though the values are lower than the compressive

strength of concrete containing only natural aggregate[13].

Frigione reported that the compressive strength of concrete

prepared by replacing 5% in weight of natural fine aggregate by

PET waste aggregate (PETW) is slightly lower (not lower than 2%)

than that of concrete containing natural aggregate [23]. According

to the author, the compressive strength of PETW concrete increases

from 28 to 365 days similarly to what is observed for the speci-

mens without PETW. The big differences in strength between con-

crete containing PETW aggregate and that containing natural

aggregate was observed for low cement content and, most of all,

for high values of the w/c ratio. According to the author, this is

due to the higher content of bleeding water in concrete mixes con-

taining PETW than in the conventional concrete mix. This water in

the concrete mix containing PETW is located mostly around the

aggregate particles of PETW and produced a weaker bond between

the cement matrix and PETW.

Kou et al. reported that the compressive strength of concrete

containing PVC granules derived fromscraped PVC pipes decreased

with the increase in PVC granules content[9]. The reduction in 28-

day compressive strength of the lightweight concrete mixes pre-

pared by replacing 5%, 15%, 30% and 45% of natural fine aggregate

by PVC granules were respectively 9.1%, 18.6%, 21.8% and 47.3%

with respect to the control mix. The lower elastic modulus of

PVC aggregate compared to normal fine aggregate, higher particle

size of PVC aggregates than natural fine aggregate, and low bond-

ing strength between PVC aggregate and cement paste due to

internal bleed water from the fully saturated lightweight aggre-

gates that accumulated and surrounded the waste PVC granules

are the reasons behind the strength reduction.

Hannawi et al. reported the 28-day compressive strengths of ce-

ment mortar containing PET and polycarbonate (PC) aggregates

prepared by replacing 3%, 10%, 20% and 50% of sand [18]. A de-

crease in compressive strength was observed when the plastic

aggregates in mortar content increased. For the same substitution

rate, the reduction in compressive strength of the mortar contain-

ing PET aggregate was greater than that of the mortar containingPC aggregate. A decrease in compressive strength of 9.8%, 30.5%,

47.1% and 69% for mixes with, respectively, 3%, 10%, 20% and 50%

of PET aggregates, and of 6.8%, 27.2%, 46.1% and 63.9% for mixes

containing, respectively, 3%, 10%, 20% and 50% of PC-aggregates

was observed. The compressive strength of the mortar was propor-

tional to their dry unit weight.

Marzouk et al. reported that the 28-day compressive strength of

mortar containing plastic aggregate decreased slightly, by 15.7% in

comparison with the reference mortar when the sand volume re-

placed by aggregates increased from 0% to 50%[6]. However when

the rate of substituted aggregate exceeded 50%, the mechanical

properties including compressive strength fell sharply. Akcaozoglu

et al. investigated the utilisation of shredded waste polyethylene

terephthalate (PET) bottle granules as a lightweight aggregate inmortar preparation using two types of binders: normal Portland

cement (NPC) and a 50:50 mixture of blast furnace slag (bfs) and

NPC [1]. The authors found that the compressive strength of mortar

containing PET aggregate is higher for the binder prepared by using

NPC-bfs than the same property for only NPC mortar.

Panyakapo and Panyakapo reported that the concrete contain-

ing melamine waste aggregate as a partial replacement of natural

fine aggregate and fly ash as a partial replacement of normal Port-

land cement met most of the requirements for non-load bearing

lightweight concrete according to ASTM C129-05 Type II standard

though strength decreased with the introduction of plastic waste

in concrete[11].

Fraj et al. detected 5778% lower 28-day compressive strength

values of concrete containing rigid polyurethane (PUR) foam with asize of 820 mm as aggregate compared to the control concrete,

due to the lightweight nature of the concrete as well as the low

mechanical properties and the high porosity of PUR foamaggregate

[19]. Pre-wetting the PUR foam aggregate further lowers the com-

pressive strength due to the increase of the mortar porosity. On the

other hand the addition of superplasticizer along with an increase

in cement content increases compressive strength. The use of

superplasticizer made it possible to decrease cement content by

15% and to increase PUR foam content by 33% compared, with an

acceptable reduction (15%) of compressive strength. The concrete

containing dry PUR foam aggregate almost satisfied the criteria

of structural lightweight aggregate concrete as defined in ACI

318 and ASTM C 330.

Mounanga et al. reported that water curing of concrete contain-

ing PUR foam aggregate and normal aggregate slightly improved

the compressive strength compared to the corresponding value

after dry-state curing[20]. For normal lightweight concrete the in-

crease in strength was about 69% and this improvement for con-

crete containing 13.1%, 21.2% and 32.7% in volume of PUR foam

aggregate was 39%, 34% and 5% respectively.

Kan and Demirboga reported that lightweight concrete contain-

ing heat-treated expanded polystyrene (MEPS) waste aggregate

exhibited 40% higher compressive strength than concrete contain-

ing vermiculite or perlite aggregate at equal concrete density[15].

However, the compressive strength of concrete containing MEPS

aggregate decreased with increasing incorporation of aggregate.

The development of compressive strength of concrete containing

100% MEPS aggregate after 7 day with respect to 90 day strength

was about 83% whereas the same for concrete containing 25%

MEPS aggregate was 69%, which might be due to the high hydra-

tion heat of the former type of concrete because of low specific

thermal capacity of the MEPS aggregate. The compressive strength

of concrete containing coarse MEPS aggregate was lower than that

of the concrete containing fine MEPS aggregate as the coarse MEPS

aggregate had higher porosity and was therefore more brittle and

weaker than the fine MEPS aggregate.

Laukaitis et al. found that the compressive strength of the com-

posite prepared by using crumbled recycled foam polystyrenewaste as well as spherical large and fine blown polystyrene waste

as granular additive depends on the density of the composite and

the type of granules used[28]. The order of compressive strengths

of the composite at equal density was: fine granules > large gran-

ules > crumbled granules. According to the authors, the higher

compressive strength of composite containing fine granules was

due to the formation of uniform monolithic bulk structure with

uninterrupted pores where the fine polystyrene granules were

evenly spread. On the other hand, the structure of the composite

containing large granules was damaged, and the pores were par-

tially disintegrated.

3.3.2. Splitting tensile strength

Similarly to the behaviour of compressive strength, the incorpo-ration of any type of plastic aggregate lowers the splitting tensile

strength of concrete. The causes for the reductions observed in

splitting tensile strength reported in various references were sim-

ilar to those used to explain the decrease in compressive strength

due to the incorporation of plastic aggregate. Some results on the

tensile strength behaviour of concrete and mortar containing var-

ious percentages of different types of plastic aggregates are pre-

sented inFig. 7.

Frigione found lower values of splitting tensile strength in con-

crete containing PET aggregate prepared using high w/c value than

in a similar mix prepared at low w/c value[23]. Kou et al. reported

that the splitting tensile strength was reduced with an increase in

PVC content in a manner similar to that observed for compressive

strength [9]. According to them, the splitting tensile strength ofconcrete is influenced by the properties of the interfacial transition



9/17

zone (ITZ) and therefore the smooth surface of the PVC particles

and the free water accumulated at the surface of PVC granules

could cause a weaker bonding between the PVC particles and the

cement paste. According to Albano et al. the decrease in splitting

tensile strength was due to the increased porosity of concretecaused by the incorporation of PET aggregate as well as the in-

crease in w/c ratio[2]. Kan and Demirboga also reported that the

splitting tensile strength of concrete containing heat-treated ex-

panded polystyrene (MEPS) aggregate decreases with its increasing

content in concrete, due to the generation of more porosity be-

cause of the incorporation of MEPS[15]. Batayneh et al. reported

that the decreasing trend of splitting tensile strength was not as

prominent as that for compressive strength[24]. Saikia and de Bri-

to also reported lower 28-day tensile strength of concrete contain-

ing three differently shaped PET aggregates [25]. The authors

reported that the concrete cylinders containing flakier PET aggre-

gate did not split into two fractions after determination of tensile

strength, which is generally observed for cylinders containing nat-

ural and pellet plastic aggregates, since the flaky-shaped plastic

aggregate can act as a bridge between the two split pieces.

Kou et al. found an excellent correlation between the 28-day

splitting tensile strength and the 28-day compressive strength of

concrete containing PVC aggregate as replacement of fine natural

aggregate, which follows a linear relationship [9]. Choi et al. also

found an expression,fst 0:23 f1=3c , for the relationship betweenthe 28-day compressive strength and the splitting tensile strength

of concrete containing PET aggregate and an expression,

fst= 1.40 (fc/10)(1/3), for a similar relationship for conventional

concrete [3].Fig. 8 shows the relationship between splitting tensile

and compressive strengths.

3.3.3. Modulus of elasticity

According to ASTM C 469, the modulus of elasticity is defined as

a stress to strain ratio value for hardened concrete. The type of

aggregate influences this modulus, since the deformation produced

in concrete is partially related to the elastic deformation of theaggregate. The effect of plastic waste aggregate on the behaviour

of concretes modulus of elasticity is reported in a few publications

and some results are presented inFig. 9.

From their study on the use of three size fractions of PET waste

aggregate in the preparation of concrete, where concrete was pre-

pared at two w/c ratios and with two natural fine aggregate

replacement levels, Albano et al. concluded that: (1) a higher mod-

ulus was achieved with 10% of PET at a fixed particle size than with

the 20% of PET in concrete since PET is less resistant than sand and

would deform less when an equivalent stress is applied; (2) for the

same amount of PET, the particle size had no detrimental effect on

the modulus of the concrete; (3) at both w/c values, the trends ob-

tained were similar for the three particle sizes and for the two PET

contents; (4) a higher modulus of elasticity was observed for con-crete prepared at w/c of 0.50 then for that prepared at w/c of 0.60,

due to the greater porosity in the concrete prepared at higher w/c

value; (5) the observed modulus of elasticity of concrete contain-

ing PET aggregate met the requirement as described in American

Manual of Reinforced Concrete (1952) except the concrete com-

position prepared by using 20% large sized PET aggregate at w/c

of 0.60[2].

Frigione plotted the stressstrain curves (re curve) during

determination of compressive strength of the reference as well as

a PET containing concrete prepared at w/c of 0.45 with cement

content of 400 kg/m3 [23]. The strain values corresponding to the

maximum stress for the concrete containing PET aggregate and

the reference concrete were 0.0018 and 0.0020 respectively. The

elastic modules calculated from the re curve were 48.1 and

41.8 GPa for the reference concrete and the concrete containing

PET, respectively.

Marzouk et al. reported that the modulus of elasticity values (as

determined by the ultrasonic method) decreased as PET quantity

increased [6]. Compared with the modulus of elasticity of reference

mortar (27.94 MPa), a 50% reduction was observed for the mortar

prepared by replacing 50% of fine natural aggregate by PET aggre-

gate. The reduction in modulus of elasticity was due both to the

reduction of mortars bulk densities and to the presence of plastic

0

1

2

3

4

0 10 20 30 40

Spl.te

nsilestrength(MPa)


Control [A]

Coarse [A]

Fine [A]

Pellet [A]

Control [B]

Coarse [B]

Fine [B]

Mix (1:1) [B]

[C]

[D]

Fig. 7. Splitting tensile strength of concrete containing plastic waste aggregate

containing plastic aggregate: [A]:[25]; [B]:[2]; [C]:[24]; [D][9].

Fig. 8. Relationship between the compressive strength and the splitting tensile strength of concrete containing plastic aggregate.



10/17

aggregates, which decreased the velocity of wave by disturbing the

ultrasonic wave propagation.

Hannawi et al. found that the increasing plastic content in con-

crete decreased the resulting elastic modulus, probably due to the

low values of elastic modulus of PET and PC plastics as well as the

poor bond between the matrix and plastic aggregates [18]. Saikia

and de Brito also found lower modulus of elasticity for concrete

containing three differently shaped PET waste aggregates than that

for concrete containing natural aggregate[25]. According to them,

the lowering of modulus of elasticity of concrete due to incorpora-

tion of PET aggregates is due to the lower modulus of elasticity of

PET aggregate than that of the natural aggregate as well as to the

generation of higher porosity due to a higher w/c value.

Compared to compressive strength, Fraj et al. observed a less

significant effect on the modulus of elasticity due to the incorpora-

tion of fine expanded polyurethane (PUR) foam aggregate in light-

weight concrete[19]. The same authors found an increasing linear

correlation between air-dry density and dynamic modulus of elas-

ticity. As the PUR foam had a low elastic modulus due to its high

porosity, increasing the content of PUR foam in concrete reduced

the elastic modulus of resulting concrete. Pre-wetting of PUR foamaggregates, improving the cementitious matrix properties by using

super plasticizer and decreasing the w/c ratio did not have influ-

ence on the modulus of elasticity.

Increasing the replacement amount of fine aggregate by PVC

granules in concrete also reduced the resulting elastic modulus

[9]. The replacement of 5%, 15%, 30% and 45% of fine aggregate

by PVC granules reduced the elastic modulus by 6.1%, 13.8%,

18.9% and 60.2%, respectively, when compared to that of the con-

trol concrete. According to the authors, the major causes of this

reduction were (1) lower elastic modulus of PVC granules than that

of the cement paste; (2) lower compressive strength of the con-

crete containing PVC than that of the normal concrete. They also

reported that the predictionof the modulus of elasticity of concrete

containing PVC granules by using the equation suggested by ACI

318-83 over-estimated the modulus of elasticity of concrete

(Fig. 10).

Choi et al. reported that the increasing incorporation of granu-

lated blast furnace slag coated PET aggregate in concrete decreased

the resulting elastic modulus [4]. In another study, Choi et al. com-

pared the relationship between the 28-day compressive strength

and the 28-day elastic modulus of concrete containing various pro-

portions of sand coated PET aggregate as a replacement of fine nat-

ural aggregate with CEB-FIP model code (CEB Bulletin Information

No. 213/214: Comit Euro-international du Bton, 1993) and ACI

code (ACI 318M-05: Building code requirements for structure con-

crete and commentary; ACI Manual of concrete practice, 2005)[3].

The relationship between the compressive strength and elastic

modulus of concrete containing plastic aggregate was in close

agreement with the relationship suggested in ACI 318-05, in which

the concretes density was taken into consideration (Fig. 10).

Laukaitis et al. determined the elastic modulus of composites

prepared by using three types of polystyrene waste beads [28].

Their results indicated that the modulus of elasticity depended

on the density of composite and the type of beads.

3.3.4. Flexural strength

Flexural strength is defined as the materials ability to resist

deformation under flexural load and is measured in terms of stress.

It represents the highest stress experienced within the material at

the collapse load. The transverse bending test is most frequently

employed, in which a specimen with either a circular or rectangu-

lar cross-section is bent until fracture using a three or four point

flexural test technique. Fig. 11 presents a fewtypical results of flex-

ural strength of concrete and mortar containing various amounts ofplastic aggregate.

Akcaozoglu et al. determined the ratios between flexural

strength and compressive strength values of cement mortar, pre-

pared using various conditions[1]. The authors found average val-

ues of flexural strength similar to those of normal weight mortar.

Batayneh et al. also reported a decreasing trend of flexural strength

with increasing plastic waste aggregate content in the concrete

0

10

20

30

40

0 10 20 30 40 50

Elasticmodulus(GPa)


[A]

[B] type A

[C] type C

[B] type D

[C] fine

[C] coarse

[C] mix (1:1)

Fig. 9. Elasticity modulus of concrete and cement mortar with plastic aggregate:

[A]:[18]; [B][6]; [C][2].

Fig. 10. Relationship between compressive strength and modulus of elasticity of concrete containing plastic aggregate.



11/17

[24]. However, this reductionwas not as significant as for compres-

sive strength. Ismail and Al-Hashmi reported the flexural strength

of concrete containing 10%, 15% and 20% of plastic waste as a

replacement of fine natural aggregate [13]. Their results showed

that the flexural strength of plastic waste concrete mixes at each

curing age was prone to decrease with the increase of the plasticwaste ratio in these mixes. Saikia and de Brito also found lower

flexural strength values for concrete containing PET aggregate than

for concrete containing natural aggregate only[25].

Hannawi et al. reported they did not find significant changes in

the flexural strength of mortar specimens containing up to 10% of

PET aggregates and up to 20% of PC aggregates compared to a con-

trol mix [18]. However, a decreased of 9.5% and 17.9% for mixes

with, respectively, 20% and 50% of PET aggregates was observed.

For mixes with 50% of PC aggregates a decrease of 32.8% was mea-

sured. According to the authors, the elastic nature and the non-

brittle characteristics under loading of the plastic aggregate might

have an effect on the observed flexural strength. The flexural

strength of cement composites prepared by Laukaitis et al., using

three various types of polystyrene waste granules followed a pro-

portional relationship with their density [28].

3.3.5. Toughness/Poisons ratio

Ismail and Al-Hashmi plotted the loaddeflection curves of the

reference concrete and of concrete mixes prepared with 10%, 15%,

and 20% plastic waste as fine natural aggregate replacement at the

curing ages of 3, 7, 14, and 28 days[13]. The curves are illustrated

inFig. 12. They show the arrest of propagation of microcracks due

to the introduction of plastic waste particles in concrete. The

authors also evaluated the toughness indices for concrete compo-

sitions containing plastic waste aggregate at the curing ages of 3,

7, 14, and 28 days (Table 8).

For all concrete mixes at 14 and 28 days curing ages, the tough-

ness indices of those containing plastic waste aggregate for all

replacement levels complied with the plastic behaviour according

to ASTM C1018, desirable for many applications that require high

toughness. Frigione plotted the stressstrain curves (re curve)

during determination of compressive strength of the reference as

well as PET containing concrete [23]. Compared to the reference

mix, a higher strain value corresponding to the maximum stress

was registered for the concrete containing PET waste aggregate.The peak shapes of the two curves also suggested that the concrete

containing PET waste aggregate is less brittle than the reference

concrete. The failure modes registered for concrete containing

PET waste aggregate indicated that this type of concrete could

withhold a larger deformation while still keeping its integrity

(Fig. 13).

Kou et al. observed an increasing Poissons ratios with increas-

ing contents of PVC waste aggregate in concrete[9]. As the higher

Poissons ratios meant higher ductility, the incorporation of PVC

improved the ductility of the resulting lightweight aggregate con-

crete, due to the elastic nature of PVC.

Hannawi et al. plotted the flexural loaddeflection curves of

concrete containing various percentages of PET and PC waste

0

2

4

6

0 10 20 30 40 50

Flexuralstrength(MPa)


PET [A]

PC [A]

Coarse [B]

Fine [B]

Pellet [B]

Fig. 11. Flexural strength behaviour of cement mortar and concrete containing

plastic aggregate: [A][18]; [B][25].

Fig. 12. Loaddeflection curves of concrete prepared by replacing fine aggregate by (A) 0% plastic waste (reference); (B) 10% plastic waste; (C) 15% plastic waste and (D) 20%plastic waste[13].



12/17

aggregates as a replacement of fine natural aggregates[18]. Their

results showed an improvement in ductility when the plastic

aggregates content increased. The authors found an increase in

the flexural toughness factor for mixes containing PET and PC

aggregates (Table 9). The toughness factor was calculated from

the experimental flexural loaddeflection curves. The greateramount of plastic aggregates resulted in a greater toughness for

both PC and PET plastic mixes. This indicated that the incorpora-

tion of plastic aggregate could lead to high energy absorbing

materials.

3.3.6. Failure characteristics

After failure during determination of compressive strength,

specimens containing plastic aggregates do not exhibit the typical

brittle type of failure for conventional cement mortar and concrete.

As the plastic aggregates content increases the failure becomes

more ductile. The specimens containing plastic aggregates can car-

ry load for a few minutes after failure without full disintegration,

which was observed by various investigators[6,18,25].

Albano et al. found various types of failure including normalcone type for concrete specimens prepared by replacing 20% of fine

natural aggregates (Fig. 14)[2]. As the smooth surface of the PVC

particles and the free water accumulated at the surface of PVC

granules could cause a weaker bonding between the PVC particles

and the cement paste, most of the PVC granules in the concrete

matrix did not fail, but were debonded from the cement paste after

reaching their ultimate stress[9]. Fraj et al. reported that the rup-

ture mechanism of concrete containing PUR foam aggregate was

different from that of normal weight control concrete: in the case

of concrete containing PUR foam aggregate, rupture occurred on

the mortar matrix/PUR foam aggregate interfaces as well as in

the middle of the PUR foam aggregate[19]. On the other hand, in

normal weight concrete rupture mainly took place in the ITZ be-

cause of the poor properties of this zone compared to the other

concrete components. From the observation of the splitting behav-

iour of concrete blocks after tensile strength and flexural strength

tests, Saikia and de Britoconcluded that flaky PET aggregate canact

as bridge between the two split pieces of concrete specimen after

failure, which was not observed in concrete specimens containing

natural as well as pellet PET aggregate[25].

3.3.7. Abrasion resistance

Compared to other properties, very few information is available

on the abrasion resistance behaviour of concrete (or mortar con-

taining any type of plastic waste aggregates. Soroushian et al. only

reported the abrasion resistance of concrete containing plastic

waste fibre [14]. The authors found a reduction of the abrasion

resistance of concrete due to the incorporation of plastic waste fi-

bre in concrete. However, the incorporation of the commercial

plastic aggregate in concrete improved the abrasion resistance of

the resulting concrete[29].

Recently Saikia and de Brito reported that the incorporation of

PET aggregate can improve the abrasion resistance of concrete

(Fig. 15A) [25]. The authors found that the abrasion resistance of

concrete containing pellet PET aggregate increased with increasing

content. On the other hand, for the mixes containing two types of

flaky aggregates the best results were obtained for 10% substitu-

tion level. From the relationship between compressive strength

and depth of wear for concrete containing different types of plastic

aggregates, the authors found a given compressive strength level

for concrete containing PET aggregate over which the abrasion

resistance deteriorates (Fig. 15B).

3.4. Durability performance

Several durability factors are evaluated for concrete or mortar

containing plastic as aggregate. These include water absorption

and sorptivity, shrinkage, carbonation resistance, chloride ion per-

meation and resistance against freezing and thawing. However,

compared to the available information on mechanical performance

of concrete containing plastic aggregate, there is less information

on the durability behaviour of concrete of this type of concrete.

3.4.1. Permeability behaviour

Generally the permeability of aggressive chemical speciesthrough the pores of concrete is the major factor that controls sev-

Table 8

Toughness indices for concrete containing various percentages of plastic wastes as a replacement of fine aggregate [13].

Percentages of plastic in concrete mixtures (%) Toughness indices at curing ages

3-days 7-days 14-days 28-days

I5 I10 I10:I5 I5 I10 I10:I5 I5 I10 I10:I5 I5 I10 I10:I5

10 8.3 11.6 1.4 4.3 8.6 2.0 2.5 7.5 3.0

15 3.0 11.0 3.7 4.5 9.5 2.1 4.2 8.4 2.0 8.0 16.1 2.0

20 6.8 13.7 2.0 7.3 14.8 2.0 5.2 11.5 2.1 5.7 11.6 2.0

Fig. 13. Stressstrain curves for reference concrete (plain line) and concrete

containing PET waste aggregate (dotted line) [23].

Table 9

Flexural toughness factors for concrete containing various amounts of PET and PC

waste aggregates[18].

Concrete type Flexural toughness factors

rb150 (MPa) rb100 (MPa) rb50 (MPa)

Control 0.44 0.32 0.15

3% PET 0.51 0.39 0.24

10% PET 0.60 0.46 0.30

20% PET 0.92 0.73 0.48

50% PET 1.66 1.31 0.85

3% PC 0.58 0.49 0.37

10% PC 0.91 0.77 0.57

20% PC 1.08 0.92 0.74

50% PC 1.45 1.26 0.95



13/17

eral durability properties. Tests like water absorption, gas perme-

ability, and chloride permeability measurement can provide infor-

mation on the vulnerability of concrete to the ingress of

deleterious chemical species.

3.4.1.1. Water absorption and water accessible porosity. Albano et al.

reported higher water absorption for concrete containing PET

aggregate than for concrete containing natural aggregate only [2].

The water absorption is further increased with increasing content

of PET aggregate in concrete, increasing size of PET aggregate andincreasing w/c ratio. According to the authors, the difference in size

distribution as well as in shape of plastic aggregate from the fine

natural aggregate was responsible for this behaviour.

Marzouk et al. reported that volumetric substitutions of plastic

aggregate lower than 100% decreased the rate of water adsorption

with respect to the reference mortar that contained no waste [6].

The authors carried out the adsorption of steam water in the differ-

ent cement mortar specimens in a temperature-controlled room

under saturated atmosphere (100% relative humidity and

2 0 2 C). They also determined the sorptivity of various cement

mortars at ambient temperature, by placing one surface of the

dried samples in contact with liquid water. The mass increase

per unit area was then plotted against the square root of time,

which gave a straight line. The water absorption coefficient orthe sorptivity was then determined from the slope of line. The

authors found lower sorptivity for cement mortars containing

PET aggregate than for mortars containing no plastic waste

(Fig. 16). The sorptivity further decreased with increasing volume

of substitution up to 50%. Thus their results suggest better durabil-

ity performance of cement mortar containing PET aggregates then

of mortar containing natural aggregate only if it comes into contact

with aggressive solutions.

Choi et al. measured the sorptivity coefficient of 28-days cured

cement mortars prepared by replacing 0%, 25%, 50% and 75% of fine

natural aggregate by sand powdered coated PET aggregate [3].Their results indicated that the sorptivity of cement mortar con-

taining PET aggregate at 25% replacement level was lower than

the control mortar and for 50% and 75% replacement level it was

higher than the control mortar. According to the authors, at 50%

and 75% replacement level, the change in grading size of the fine

aggregate mixture increased the inside porosity of mortar and thus

increased the sorptivity.

Hannawi et al. measured the water absorption and apparent

porosity values of the different concrete mixes containing various

amounts of PET and polycarbonate (PC) waste aggregates [18].

Their results revealed that replacing 3% (in volume) of sand by

an equal volume of PET or PC waste does not exert influence either

on water absorption or on apparent porosity of the composites in

comparison with the control mortar. However apparent porosityand water absorption increased with increasing plastic content.

Fig. 14. Types of failures observed in the cylinders after compressive strength testing: (A) longitudinal, (B) cone, (C) border, (D) diagonal[2].

Fig. 15. (A) Depth of wear of concrete with various percentages of replacement of NA by PET aggregates after abrasion resistance test; (B) cubic compressive strengthversus

depth of wear[25].



14/17

Akcaozoglu et al. found higher water absorption and porosity

values for a cement mortar containing 100% PET aggregate than a

mortar containing a mixture of equal percentage in volume of

PET aggregate and sand[1]. The authors found a similar trend for

cement mortar containing a mixture of equal weight of blast fur-nace slag and normal Portland cement (NPC) though the blast fur-

nace slag addition with NPC increases the water absorption and

porosity of the resulting cement mortar. However, according to

the authors, all the values for all types of mortar meet the range

that is generally observed for lightweight concrete.

Fraj et al. recorded a higher value of the water accessible poros-

ity of cement mortar containing polyurethane (PUR) foam aggre-

gate than that of mortar containing no plastic aggregate [23]. The

authors also reported that pre-wetting of PUR foam aggregate fur-

ther increased the porosity. However the addition of a super plas-

ticizer to the cement mortar containing pre-wetted PUR foam

aggregate can decrease its porosity.

3.4.1.2. Gas permeability. Hanawi et al. evaluated the apparent per-meability of concrete prepared by replacing different percentages

of fine aggregate by PET and PC aggregate using helium gas under

0.2 MPa pressure [18]. The authors found an increase of the perme-

ability coefficient with increasing plastic aggregates content in

concrete, which indicated an increase of the percolated porosity

of concrete due to the incorporation of plastic aggregate. According

to the authors, the increase in porosity due to weak bonding be-

tween the cement paste and plastic aggregate is the cause of the

higher permeability of concrete containing plastic aggregate. They

also reported greater percolated porosity of concrete containing

PET aggregate than that of concrete containing PC aggregate at

the higher replacement level (10%, 20% and 50%).

Fraj et al. reported higher permeability of concrete containing

dry and pre-wetted PUR foam aggregate than of conventional con-crete[19]. The permeability of concrete containing dry PUR foam

aggregate is 2.2 times higher than that of conventional concrete.

Pre-wetting of PUR foam aggregate can increase the value consid-

erably. Decreasing the w/c value and increasing super plasticizer

content can reduce this value for concrete containing pre-wetted

PUR foam aggregate.

3.4.1.3. Chloride migration. Kou et al. investigated the resistance to

chloride ion penetration of 28 and 91 days hardened concrete pre-

pared by partially replacing fine natural aggregate by PVC waste

granules [9]. The chloride ion penetration resistance of concrete

was represented by the total charge passed in Coulomb during a

test period of 6 h. Their results (presented in Fig. 17) indicated that

the resistance of chloride ion penetrability of concrete increasedwith an increase in PVC content as well as with longer curing. They

found reduction of about 36% in the total charges passed through

the 28-day cured concrete, prepared by replacing 45% of natural

aggregate by PVC granules in comparison with the concrete con-

taining no waste PVC granules and the same curing age. According

to them, the increase in the resistance to chloride ion penetration

of concrete is attributed to the impervious PVC granules blockingthe passage of the chloride ion.

Fraj et al. evaluated the chloride diffusion coefficients of con-

crete containing rigid polyurethane (PUR) foam as partial replace-

ment of coarse natural aggregate[19]. Their results are presented

inTable 10. The authors observed a lower value of chloride diffu-

sion coefficient for concrete containing dry PUR foam aggregate

than that of concrete containing natural aggregates only. However,

the pre-saturation of PUR foam aggregate in water resulted in a

significant increase of the chloride diffusion coefficient, due to an

increase in porosity of concrete, which rises with increasing vol-

ume of PUR foam aggregate in concrete. They also reported that

the reduction in w/c ratio and increase in cement content could

significantly improve the chloride resistance performance of con-

crete containing pre-wetted PUR foam aggregate.

3.4.2. Carbonation

Akcaozoglu et al. measured the carbonation resistance of vari-

ous types of cement mortars by measuring carbonation depth

[1]. The phenolphthalein solution was applied on the broken sur-

faces of the half pieces obtained after flexuraltensile strength test.

The compositions of various mixes along with carbonation depth at

various time periods are presented inTable 11. Irrespective of bin-

der types, the carbonation depth of mortar containing only PET

aggregate at or after 28 days of curing are lower than that of the

mortar containing an aggregate mixture of PET and sand. The

authors also found a higher porosity of mortar containing sand

and PET mixture than the mortar containing PET aggregate only.

According to the authors, PET and sand aggregates used togetherdid not combine with each other sufficiently and therefore the

resulting mortar becomes porous. On the other hand, the depth

of carbonation for concrete containing slag is significantly higher

than the mortar prepared by using cement as the only binder.

3.4.3. Shrinkage

Frigione measured the drying shrinkage property of one year

cured concrete containing PET aggregate, which replaced 5% in

weight of fine natural aggregate [23]. The author found an increase

in drying shrinkage value due to the incorporation of PET aggregate

in concrete for the different experimental conditions. According to

the author, this behaviour is primarily due to the lower elastic

modulus of concrete containing plastic aggregate than that of con-ventional concrete. However the range of shrinkage for concrete

Fig. 16. Coefficient of sorptivity of cement mortar containing various volume

percentages of PET aggregate[6].

Fig. 17. Resistance to chloride penetration of concrete prepared by replacing

various amounts of fine natural aggregate by PVC waste granules [9].



15/17

containing PET aggregate was acceptable for various uses of struc-

tural concrete.

Fromhis experiments on the use of waste PVC granules as a par-

tial volumetric replacement of natural sand in the preparation of

concrete, Kou et al. reported a decreasing trend of drying shrinkage

with increasing content of plastic aggregates (Fig. 18)[9]. Accord-

ing to the authors, PVC granules were impermeable and did not ab-

sorb water when compared to sand and did not shrink, and hence

were able to reduce the overall shrinkage of concrete.

Fraj et al. found higher drying shrinkage for lightweight con-

crete containing dry and pre-wetted polyurethane foam (PUR

foam) as a part of fine aggregate [19]. The concrete containing

dry PUR foam aggregate has 8.1% more 28-day drying shrinkage

than the control concrete. On the other hand, concrete mixes

containing pre-wetted PUR foam aggregate for 34% and 45% (involume) replacement levels exhibited 72.5% and 149.5% higher

28-day drying shrinkage than the control concrete, respectively.

Lowering the w/c ratio or increasing the super plasticizer, sand

and cement contents can decrease the drying shrinkage of concrete

containing pre-wetted PUR foam aggregate. In these conditions,

the 28-day drying shrinkage value of concrete containing pre-

wetted PUR foam aggregate by 35% (in volume) is 49.7% higher

than that of the control concrete. According to the authors, the

lower elastic modulus of PUR foam aggregate and the higher

amount of pre-wetting water in the case of concrete containing

pre-wetted aggregate are the causes of its high drying shrinkage.

Mounanga et al. also reported higher drying shrinkage of con-

crete prepared by replacing various fractions of fine aggregate by

PUR foam aggregate than that of the control concrete[20]. Accord-

ing to the authors, this behaviour was mainly due to the effect of

PUR foam aggregate on the stiffness of concrete. However some

other factors such as the w/c ratio, sand content and thermal dila-

tion during hydration also had a significant effect.

Akcaozoglu et al. observed significantly higher drying shrinkage

values of mortars containing PET aggregate only than that exhib-

ited by a mortar containing equal weight percentage of sand and

PET aggregate at the experimental drying periods[1]. Mixing blastfurnace slag with cement can reduce the shrinkage values for both

type of aggregate (PET only and sand-PET mix) containing mortars.

3.4.4. Freezing and thaw resistance

Kan and Demirboga reported the freeze and thaw resistance of

concrete containing modified expanded polystyrene foam (MEPS)

as partial or full substitution of fine and coarse natural aggregates

by using standard method, ASTM 666 procedure B [15]. The follow-

ing conclusions were taken from the results: (1) by increasing the

MEPS aggregate ratio in mixes, the concrete is expected to exhibit a

higher frost resistance and have a higher durability; (2) coarse

lightweight MEPS aggregate is more susceptible to the freezethaw

cycles when compared to the fine light-weight aggregate.

3.5. Other properties

3.5.1. Fire behaviour

Albano et al. determined the fire behaviour of concrete contain-

ing various percentages of shredded PET aggregate as partial

replacement of fine natural aggregate[2]. The authors placed the

cured slabs in a muffle furnace, the temperature inside the furnace

was increased up to a pre-determined temperature, the slabs were

kept at that temperature for 2 h, and then heating was stopped

immediately. The temperatures chosen for this study were 200 C,

400 C and 600 C. After coolingthe specimen to room temperature,

the flexural strength was determined. In parallel, unheated speci-

mens were tested. Their results are presented in Fig. 19.

As the temperature increased, the flexural strength decreasedregardless of the level of substitution and the PET particle size.

Table 10

Chloride ion penetration co-efficient of concrete containing PUR foam aggregate, mm [19].

Volume of PUR foam aggregate w/c ratio Cement content (kg/m3) Volume content

of PUR foam (%)

Amount of superplasticizer (kg/m3) Effective chloride diffusivity

coefficient (1012 m2/s)

Control 0.55 397 0 0 1.87

Dry PUR aggregate 0.55 397 34 0 1.62

Pre-wetted PUR aggregate 0.55 397 34 0 5.30

0.44 415 35 1.405 2.70

0.44 353 45 1.196 5.98

Table 11

Depth of carbonation of various cement mortar specimens [1].

Amount in mortar (%) Depth of carbonation (mm)

Cement Slag PET aggregate Normal aggre

Effect of impact load in 12 story building

Documents

Transcript of Effect of impact load in 12 story building