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Utilisation of Waste Plastics for Improving the performance of Bituminous Road Pavements

CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION

Highway, as we know, is one of the most essential elements of modern day traffic

system, without which the 21st century traffic system itself will fail. As the name

suggests, Highway means “elevated way” for the traffic to move without any discomfort

and the name has got its origin from the roman era, dated back around 500 BC, who built

roads at a higher ground level than the normal ground level. The traffic that can be

carried depends on the highway pavement characteristics. Highway pavements can be

classified into rigid pavements and flexible pavements mainly based on the materials

used for construction. Though, Rigid Pavement has got many advantages over the

Flexible Pavements, however, based on the Indian natural conditions and economy, the

Flexible Pavement has been preferred most of the times.

Flexible pavements are a crucial part of India’s strategy for building a high

performance transportation network for the future. The increased volume of heavy goods

vehicles coupled with an appreciable increase in allowable axle weights for these

vehicles, has lead to dramatic increase in level of stresses exerted on pavement surfaces.

Furthermore congestion and economic costs of road maintenance has resulted in need toenhance flexible pavement performance.

Properties of materials in all layers of the road structure are of great importance

for the life of the road. Several factors influence the performance of flexible pavements,

for example properties of components (binder, aggregates and additives) and proportion

of these components in mix. Over the years, many different types of materials have been

proposed as additives in bituminous mixes. Investigations have revealed that properties of

bitumen and bituminous mixes can be improved to meet the requirements of the pavement with the incorporation of certain additives or blend of additives. These

additives are called bitumen modifiers and bitumen premixed with these modifiers is

known as “Modified Bitumen”.

Department of Civil, MVJCE 1




On the majority of the world’s roads and airports, conventional penetration grades

of bitumen are used as the binder for bituminous mixes. However, the working

environment of our roads is becoming more complex and severe, year by year. In recent

years, more interest is coming up in the use of polymer modifiers for bituminous mixes.

For a polymer to be effective in road applications, it should blend with the bitumen and

improve its resistance to various pavement distresses at low and high temperatures

without making the modified bitumen too viscous at mixing temperatures or too brittle at

low temperatures. In other words, it must improve the overall performance of the

pavement.

Two basic types of polymer used in modifying bitumen for road applications are

elastomers and plastomers. Poly-ethylene is a plastomer used for improving the

properties of bituminous mix used for flexible pavement construction.

1.2. USE OF WASTE PLASTIC IN BITUMINOUS PAVEMENTS AND WASTE

MANAGEMENT

Environmental issues are, now a day, of high importance. Plastic wastes, for an

instance, possess great threat to the environment, especially in urban areas, in terms of its

misuse, its dumping in the dustbins, clogging of drains, reduced soil fertility and aesthetic

problem etc. As it is non-degradable, waste plastics are also burnt for apparent disposal,

causing environmental pollution, which in turn damages the ozone layer that surrounds

the earth, because of the liberation of poisonous gases like carbon monoxide. There are

over 10,000 different kinds of plastic in the world, and it is so versatile and can be mixed

with so many other elements that its uses are limitless. It is estimated that approximately

10 thousand tons per day (TPD) of Plastic waste is generated i.e. 9 % of 1.20 lakhs TPD

of municipal solid waste (MSW) in India. They also have very long lifetime and the

burning of plastics waste under uncontrolled conditions could also lead to generation of

many hazardous air pollutants (HAPs) depending upon the type of polymers and

additives used. However, the end-of-life plastics can be recycled into a second life

application but after every thermal treatment, degradation of plastics takes place to a

certain extent. Only 5% of all plastic is recycled, so we need to push for more plastic

recycling practices in our daily lives.





Recent researches on road pavement shows that waste plastic can be mixed with

bituminous mix for construction of road pavements, which can actually enhance the

qualities of road pavement, in terms of strength, resistance, shelf life and economy, along

with a better way of waste management for these waste plastics with causing minimum

damage to the environment. Hence, here comes the concept of using the plastic wastes in

molten states with bitumen while constructing the road pavement of highways.

The waste plastic for our investigation has been procured from “KK Plastic

Waste Management Pvt. Ltd, Bangalore”. The waste plastic procured is having a

specific gravity range of 1.03 and a Melting Temperature of 75°C - 138°C. Our sole aim

is to find the optimum bitumen content as well as the optimum plastic content which can

be efficiently used in the construction of Flexible Pavements for Highways. For that

purpose, we have adopted the Dry process of mixing.

1.3 ORGANIZATION OF THE REPORT

For the ease of understanding and better assimilation, the work is divided into

various chapters.

Chapter 1: This chapter gives a general introduction on the use of polymer modified

bitumen as a way to improve the performance of bituminous mixtures, use of waste

plastic in bituminous mix and waste management.

Chapter 2: An overview of the study of literature pertaining to the research, scope and

objectives of the present investigation.

Chapter 3: The chapter presents determination of individual engineering properties of

materials used.

Chapter 4: The chapter presents determination of optimum bitumen content for the

bituminous mix.

Chapter 5: The chapter presents determination of optimum blend of waste plastic along

with the bitumen.

Chapter 6: This chapter summarises the study along with conclusions and scope for

further study.

CHAPTER 2





• It has decreased Penetration value. Hence its load carrying capacity is

increased.

• The blend with aggregate has no stripping value. So it can resist the effect of

water

• The Marshall Stability value is high.

• The bitumen required can be reduced depending upon the % of polymer

added. It is a good saving too.

A deliberate effort has been made to explore the possibilities of binding bitumen

with plastic wastes to improve the quality of the road pavement by Dr. S. S. Verma

through the journal paper, “Roads from plastic waste”, published in The Indian

Concrete Journal, November 2008.

The basic process involved in this study was that waste plastic is ground and

made into powder; 3 to 4 % plastic is mixed with the bitumen. Plastic increases the

melting point of the bitumen and makes the road retain its flexibility during winters

resulting in its long life. It has been noticed prominently that use of shredded plastic

waste acts as a strong “binding agent” for tar, making the asphalt last long. By mixing

plastic with bitumen the ability of the bitumen to withstand high temperature increases.

The plastic waste is melted and mixed with bitumen in a particular ratio. Normally,

blending takes place when temperature reaches 45.5°C but when plastic is mixed, it

remains stable even at 55°C. The vigorous tests at the laboratory level proved that the

bituminous concrete mixes prepared using the treated bitumen binder fulfilled all the

specified Marshall mix design criteria for surface course of road pavement. There was a

substantial increase in Marshall Stability value of the bituminous concrete mix, of the

order of two to three times higher value in comparison with the untreated or ordinary

bitumen. Another important observation was that the bituminous mixes prepared using

the treated binder could withstand adverse soaking conditions under water for longer

duration.

When the roads made up of waste plastic-bitumen blend and that of simple

bitumen was compared, it was seen that the durability of the roads laid out with shredded

plastic waste is much more compared with roads with asphalt with the ordinary mix.





Roads laid with plastic waste mix are found to be better than the conventional ones. The

binding property of plastic makes the road last longer besides giving added strength to

withstand more loads. While a normal 'highway quality' road lasts four to five years it is

claimed that plastic-bitumen roads can last up to 10 years. Rainwater will not seep

through because of the plastic in the tar. So, this technology will result in lesser road

repairs. And as each km of road with an average width requires over two tonnes of poly-

blend, using plastic will help reduce non-biodegradable waste. The cost of plastic road

construction may be slightly higher compared to the conventional method. However, this

should not deter the adoption of the technology as the benefits are much higher than the

cost. Plastic roads would be a boon for India’s hot and extremely humid climate, where

temperatures frequently cross 50°C and torrential rains create havoc, leaving most of the

roads with big potholes. Already, a kilometer long test-track has been tested in Karnatakausing this technology. The government is keen on encouraging the setting up of small

plants for mixing waste plastic and bitumen for road construction. It is hoped that in near

future we will have strong, durable and eco-friendly roads which will relieve the earth

from all type of plastic-waste.

The conclusions of the study were

• Plastics will increase the melting point of the bitumen

• The use of the innovative technology not only strengthened the road

construction but also increased the road life as well as will help to improve

the environment and also creating a source of income

• Plastic roads would be a boon for India’s hot and extremely humid climate,

where temperatures frequently cross 50°C and torrential rains create havoc,

leaving most of the roads with big potholes

• It is hoped that in near future we will have strong, durable and eco-friendly

roads which will relieve the earth from all type of plastic-waste.

Dr. M.V.L.R. Anjaneyulu et al. in his paper “Polymer Modified Bituminous

Mixes” has given that the optimum bitumen content related to bituminous mixes prepared

with plain bitumen and polymer modified bitumen were determined as 5% and 4.8% (by

weight of aggregate), respectively. Maximum fatigue life for plain and modified

bituminous mixes was observed at binder contents 6% and 5.5% respectively.





2.3 SCOPE AND OBJECTIVES OF PRESENT INVESTIGATION

It’s being observed that various researches are going on around the world on the

topic of use of waste plastic-bituminous mix for flexible pavement, yet there are no fixed

mathematical details which could be used as a thumb rule for the construction of thesame. Hence, the scope of our study is to evaluate the performance of Plastic tar flexible

pavement road constructed using Polymer / plastic-bitumen blend, mixed with the

aggregates.

The Objective of our study is to evaluate the performance of the pavement

constructed using waste plastic-bitumen blended bitumen, mixed with aggregates. From

the literature survey, it was found that plastic can be blended with bitumen in two ways,

viz,

• Wet process

• Dry process

Wet process:

In wet process, plastic is directly blended with bitumen in molten state at high

temperature. Then the plastic blended bitumen is mixed with aggregates at specified

temperature to obtain the bituminous mix.

Dry process:

In dry process the waste plastic is directly heated with the aggregate till it gets

coated to the aggregates. Then the bitumen is mixed with the plastic coated aggregates to

obtain the bituminous mix.

Since the available information on the numerical data related to the blending of

waste plastic with bitumen is limited, we have undertaken this investigation where

detailed experimental study has been initiated with the use of waste plastic with

bituminous mix.

The investigation is carried out under the following heads and is explained in detail in

chapter 3, 4, 5 respectively.





1. Determination of individual engineering properties of materials used.

2. Determination of optimum bitumen content of the bituminous mix.

3. Determination of optimum blend of waste plastic along with the bitumen.

CHAPTER 3

DETERMINATION OF INDIVIDUAL ENGINEERING

PROPERTIES OF MATERIALS USED

3.1 INTRODUCTION

Behavior of the bituminous mixture is affected by the properties of the individual

components like aggregates and binder and how they react with each other in the system.





When bound by the bituminous binder, mineral aggregate acts as a stone framework to

impart strength and toughness to the system. Because it is impervious to water, the binder

also functions to waterproof the mixture. The viscosity of the bitumen is quite high at

normal temperatures and has to be heated for proper mixing with the aggregate. The

function of the binder is to completely coat the aggregate creating a stable mixture of

aggregate and binder which resists the imposed stresses induced by the highway traffic

and environment. The aggregate is usually obtained from quarry sites and is produced

from the crushing of mined rock or gravel. Through the crushing operation, the fractured

aggregate takes on a variety of shapes and sizes. Shape, texture, and angularity are among

the properties of aggregates that have a significant effect on the performance of hot-mix

asphalt.

3.2 MATERIALS

The materials used in present study are given below:

• Plain bitumen: 60/70 grade (PB 60/70)

• Polymer modified bitumen: Bitumen of grade 40 modified with waste plastic.

• Aggregates and filler: Crushed coarse and fine aggregates. Ordinary Portland

cement is used as the mineral filler.

3.3 PHYSICAL PROPERTIES OF AGGREGATES

The following tests were conducted on the aggregates to study their properties.

3.3.1 Specific Gravity

The specific gravity of coarse and fine aggregate was found out separately.

Specific gravity of an aggregate is considered as a measure of the quality or strength of

the material. The specific gravity of the granite aggregates vary from 2.6 to 2.9. The test

was conducted as per IS 2386 (part III) – 1963.

3.3.2 Impact Value





Due to movement of traffic the road stones used in the surface course are

subjected to wearing action at the top. Abrasion tests are carried out to test the hardness

property of stones and to decide whether they are suitable for the different road

construction work. The principle of Los Angeles abrasion test is to produce the abrasive

action by use of standard steel balls which when mixed with aggregates and rotated in a

drum for specified number of revolutions which also cause impact on aggregates. The

percentage of wear of the aggregates due to rubbing with steel balls is determined and is

known as Los Angeles Abrasion value. The test was conducted as per IS 10070 – 1982.

3.3.7 Test Results

Various physical properties of aggregates were determined and the results are

shown in Table 3.1

Table 3.1 Aggregate Properties

Propertiestested

Sampleno:

Testresults

Average Specification IS Code

Specificgravity of

coarseaggregate

S1

S2

S3

2.608

2.725

2.604

2.65 2.6 – 2.8 IS:2386(Part-

III)-1963

Specificgravity of fineaggregate

S1

S2

S3

2.519

2.666

2.550

2.57 2.6 – 2.8

IS:2386(Part-III)-1963

Water Absorption

S1

S2

S3

0.687

0.674

0.652

0.671% 2%

IS:2386

(Part-III)-1963





Propertiestested

Sampleno:

Testresults

Average Specification IS Code

Impactvalue

S1

S2

S3

17.08

16.25

15.74

16.36% Max 24%

IS:5640-

1970

Crushingvalue

S1

S2

S3

19.09

18.94

20.35

19.46% Max 30%

IS:9376 – 1979

LosAngelesabrasionvalue

S1

S2

S3

23.9

23.6

23.4

23.63% Max 30%

IS:10070 – 1982

FlakinessIndex

S1

S2

S3

8.15

8.07

7.90

8.04% Max 25%

IS:2386(Part-I)-1963

ElongationIndex

S1

S2

S3

18.61

18.04

18.91

18.52% Max 25%

IS:2386(Part-I)-1963

3.4 BINDER PROPERTIES

From a performance point of view, bitumen is one of the most important

constituents of an asphalt mixture. The quality and properties of bitumen depend largely

on the composition of the bitumen, which is mainly controlled by the crude oil and

production process. Various tests conducted on bitumen are briefly presented.

3.4.1 Penetration Test





Penetration is a measurement of hardness or consistency of bituminous

material. It is the vertical distance traversed or penetrated by the point of a standard

needle into the bituminous material under specific conditions of load, time, temperature

and the distance that the needle penetrates into the asphalt cement is recorded in units of

0.1 mm. The test is used for evaluating the consistency of bituminous materials. The

bitumen is graded in terms of its hardness according to the penetration value. The grading

of bitumen helps to assess its suitability for use in different climatic conditions and types

of construction. In warmer regions lower penetration grades are preferred to avoid

softening whereas higher penetration grades are used in colder regions so that excessive

brittleness does not occur. The procedure for penetration test was carried out as per IS

1203-1978 and the apparatus used is penetrometer. The test has been carried out on PB

60/70.

3.4.2 Softening Point Test

The softening point of the bitumen is the temperature at which the substance

attains a particular degree of softening. It is the temperature at which a standard ball

passes through a sample of bitumen in a ring and falls through a height of 2.5 cm, when

heated in water under specified conditions of the test. The determination of softening

point helps to know the temperature at which a binder should be heated for various road

use applications. The test was carried out as per IS: 1205-1978 using the ring and ball

apparatus. The tests have been carried out on PB 60/70.

3.4.3 Ductility Test

The ductility test gives a measure of adhesive property of bitumen and its ability

to stretch. In a flexible pavement design, it is necessary that binder should form a thin

ductile film around the aggregates so that the physical interlocking of the aggregate is

improved. Binder material having insufficient ductility gets cracked when subjected to

repeated loads and it provides pervious pavement surface. Ductility of a bituminous

material is measured by the distance in centimetres to which it will elongate before

breaking when two ends of standard briquette specimen of the material are pulled apart at

a specified speed and at a specified temperature. The test was carried out as per IS: 1208-

1978 on PB 60/70.





3.4.4 Specific Gravity Test

The density of a bitumen binder is a fundamental property frequently used as an

aid to classify the binders for use in pavement jobs. The specific gravity value of bitumen

is also useful in bituminous mix design. The density of bitumen is greatly influenced by

its chemical composition. Increased amounts of aromatic type compounds or mineral

impurities cause an increase in specific gravity.

The specific gravity of bituminous material is defined as the ratio of the mass of a

given volume of the substance to the same of an equal volume of water, the temperature

of both being 27ºC. The test was carried out as per IS: 1202-1978.

3.4.5 Loss on Heating

It is the loss in mass of water, oil and other constituents of bitumen when heated at a

standard temperature of 163°C for 5 h under specified conditions of test. The test was

performed on PB 60/70 according to IS: 1212 - 1978

3.4.6 Flash and Fire point

This test is done to determine the flash point and the fire point of bitumen as per IS: 1209 –

1978. The principle behind this test is given below.

Flash Point – The flash point of a material is the lowest temperature at which the application of

test flame causes the vapours from the material to momentarily catch fire in the form of a flash

under specified conditions of the test.

Fire Point – The fire point is the lowest temperature at which the application of test flame causes

the material to ignite and burn at least for 5 seconds under specified conditions of the test.

3.4.7 Test Results





Results of the various tests conducted for PB 60/70 are given in Table 3.2 and

Table 3.3.

Table 3.2 Properties of 60/70 Grade Bitumen

Property Specimenno:

Result Average Specification IS Code

Penetration S1

S2

S3

69

65

70

68 60-70

IS:1203-1978

Softening point

S1

S2

S3

43

46

45

45 45-55

IS: 1205-1978

Ductility S1

S2

S3

82

97

92

90.33

Min 75 IS: 1208-1978

Specificgravity

S1

S2

S3

1.04

0.99

0.97

1.00 0.97-1.03

IS:1202-1978

Flash point

In °C

S1

S2

S3

205

210

205

206.67 210

IS: 1209 – 1978





Property Specimenno:

Result Average Specification IS Code

Fire point

In °C

S1

S2

S3

240

250

245

245 270

IS: 1209 –

1978

3.5 CONCLUSION

Various properties of the materials used in the study were tested in the

laboratory. Both aggregate and binder test results have found to meet the specifications.

CHAPTER 4

DETERMINATION OF OPTIMUM BITUMEN CONTENT OF

BITUMINOUS MIX

4.1 INTRODUCTION

The performance of a bituminous mix is measured in terms of its strength using

Marshall Stability test and Indirect Tensile Strength test.

The purpose of Marshall Test is to measure the strength of bituminous mixes that

had been compacted to a standard laboratory compactive effort. This test is also used as

part of the Marshall Mix design procedure for determining the optimum bitumen binder

content, and in the quality control of bituminous mixtures. Indirect tensile strength values

can be used to predict resistance of mix to permanent deformation.

4.2 EXPERIMENTAL FRAMEWORK

Marshall Stability test and static indirect tensile test were conducted on

bituminous mixes with ordinary bitumen of grade 60/70 to find the optimum bitumen

content. The specimens were prepared with binder contents of 4%, 4.5%, 5%, 5.5%, 6%





and 6.5%. Minimum three specimens were tested in each case and the average of these

test results were taken for analysis. As per IS specifications the specimens has to be

prepared with binder contents ranging from 3.5% to 7.5%. While preparing the samples it

was noticed that the components were not properly mixed using binder content 3.5%.

Since bituminous mix with 3.5% binder content is not practicable, we have not included

the samples with 3.5% bitumen binder content for our investigation.

4.3. PREPARATION OF TEST SPECIMEN

Bituminous Concrete of Grade II (IRC: 29-1968) was selected for the study

purpose. The gradation as per IRC is given in Table 4.1. The lower limit values of the

cumulative percent by weight of total aggregate passing were used in the preparation of

bituminous mix.

Table 4.1 Gradation for Bituminous Concrete

IS Sieve (mm)

passing

Cumulative percent

by weight of total

aggregate passing.

20

12.5

10

4.75

2.36

0.6

0.3

0.15

0.075

100

80-100

70-90

50-70

35-50

26-38

18-29

13-23

4-10

Following procedure was adopted for making the specimens for Marshall stability

and indirect tensile strength tests:





1. Required quantity of aggregate as per grade II as shown in Table 4.1 was heated to a

temperature of 1750C to 1950C

2. Then the required quantity of bitumen was heated to1200C to 1400C to remove all air

and water particles present

3. The heated bitumen was poured in to heated aggregate and mixed thoroughly

(manually)

4. The mixture was heated to the temperature of 1500C

5. The mixture was poured in the cylindrical moulds of 10cm diameter and applied 50

blows on each side using Marshall Hammer

6. Cylindrical moulds with specimens were allowed to cool for 24 hours and then the

specimens were removed from the moulds

4.4 MARSHALL STABILITY TEST (ASTM D: 1559-62 T)

In Marshall Stability test, the resistance to plastic deformation of cylindrical

specimen of bituminous mixture is measured when the same is loaded at the periphery at

a rate of 51mm per minute. The test procedure is used in the design and evaluation of

bituminous paving mixes.

There are two major features of the Marshall method of designing mixes namely,

i) density-void analysis

ii) stability-flow test

4.4.1 Density-Void Analysis

The properties that are of interest include the theoretical specific gravity (G t), the

bulk specific gravity of the mix (Gm), percent air voids (Vv), percent volume of bitumen

(V b), percent void in mixed aggregate (VMA) and percent voids filled with bitumen

(VFB).

Theoretical Specific Gravity (G t )





Voids in mineral aggregate VMA is the volume of voids in the aggregates, and is

the sum of air voids and volume of bitumen, and is calculated from

VMA = V v + V b

Where, Vv is the percent air voids in the mix and V b is percent bitumen content in the

mix.

Voids Filled With Bitumen (VFB)

Voids filled with bitumen VFB is the voids in the mineral aggregate frame work

filled with the bitumen, and is calculated as:

VFB= Vb×100VMA

Where, V b is percent bitumen content in the mix and VMA is the percent voids in the

mineral aggregate.

4.4.2 Marshall Stability and Flow

Specimens were prepared as per standards. Prior to the conduct of Marshall Test,

specimens were immersed in water at 60ºC for 40 min. The test was performed with

varying binder contents and the Marshall stability and flow values were determined.

Fig 4.1 Load Application in Marshall Stability Test





Marshall Stability of a test specimen is the maximum load required to produce

failure when the specimen is preheated to a prescribed temperature placed in a special test

head and the load is applied at a constant strain (50.8 mm per minute) as shown in Fig

4.1. The vertical deformation of the specimen at the failure point expressed in mm is

called the Marshall Flow value of the specimen.

It is possible while making the specimen that the thickness slightly varies from

the standard specification of 63.5 mm. Therefore, measured stability values are corrected

to those which would have been obtained if the specimens had been exactly 63.5 mm by

multiplying with appropriated correlation factors as shown in table 4.2

Table 4.2 Correction factors

Length of Specimen Correction Factors

57.1

58.7

60.3

61.9

63.5

65.1

66.7

68.3

69.9

1.19

1.14

1.09

1.04

1.00

0.96

0.93

0.89

0.86

As per IRC: 29-1968, when the specimens are compacted with 50 blows on either face, the designed bituminous mix should fulfill the following requirements.

Table 4.3 Design requirements of the mix

Design requirements of the mix





1 Marshall Stability Value (Kg) (minimum) 340

2 Marshall Flow Value, 0.25 mm units 8 to 16

3 Voids in total mix, Vv % 3 to 5

4 Voids in mineral aggregate filled with bitumen, % 75 to 85

4.4.3 Results

The mechanical properties of the bituminous mixture of plain bitumen such as

stability, flow, bulk specific gravity, air voids, voids in mineral aggregate and voids filled

with bitumen are presented in Table 4.4.

Table 4.4 Marshall Stability Test results Using Conventional Bituminous Mix

% OF

BITUMEN

CONTENT

SPECIMEN

NO:

HEIGHT-

mm

BULK SP.

GRAVITY

(Gm)

% OF AIR

VOIDS

(Vv)

% OF

VOIDS

FILLED

WITH

BITUMEN

(VFB)

MARSHALL

STABILITY

VALUES

(M)-KN

FLOW

VALUES

(δ)- mm

41 64 2.391493 1.577781 73.02227 16.79 7.65

2 64.5 2.394426 1.458922 74.64187 16.88 7.6

4.51 64.5 2.307188 1.4276731 80.06493 17.6 3.66

2 65.5 2.452282 1.3.20024 80.3569 17.52 4.55

51 64 2.49 1.118178 81.72368 19.306 3.43

2 64 2.48 1.118178 81.72368 18.834 3.2

5.51 65 2.397206 1.416428 77.9615 18.236 3.55

2 64 2.328767 1.259466 75.78922 18.256 3.59

61 65 2.317829 1.923999 67.23443 18.173 4.09

2 64.5 2.315789 2.009439 66.59682 18.46 4.17

6.5 1 64 2.332008 2.535506 76.89098 18.22 4.42





2 63 2.307692 2.562187 76.72661 17.22 4.46

4.4.4 Determination of Optimum Binder Content

Five graphs are plotted with values of bitumen content against the values of

i. Bulk Specific Gravity (Gm)

ii. Marshall Stability (S)iii. Voids in total mix (Vv)

iv. Flow Value (F)

v. Voids filled with bitumen (VFB %)

Let the bitumen corresponding to maximum bulk specific gravity (Gm) be B1,

corresponding to maximum Marshall Stability (S) be B2 and that corresponding to

minimum voids ratio (vv) be B3, then the optimum bitumen content for mix design is

given by Bo = (B1+B2+B3 )/3

The value of flow and VFB values are checked at the optimum bitumen content

Bo and the flow value should be minimum and VFB value should be maximum at

optimum bitumen content Bo. If not it should meet the specified design requirements of

the mix as given by IRC: 29 -1968

Fig 4.2 Binder Content Vs Bulk Specific gravity

From fig 4.2, the bitumen content corresponding to maximum bulk specific

gravity (B1) is obtained as 5%

Fig 4.3 Binder Content Vs Marshall Stability Value


B1=5%B2=5%




From fig 4.3, the bitumen content corresponding to maximum Marshall Stability

Value (B2) is obtained as 5%

Fig 4.4 Binder Content Vs % Air Voids

From fig 4.4, the bitumen content corresponding to minimum % of air voids (B3)

is obtained as 5%. Thus the optimum bitumen content Bo =5%

Fig 4.5 Binder Content Vs Flow Value

Fig 4.6 Binder Content Vs VFB

From fig 4.5 and 4.6 it can be seen that the flow value is minimum and VFB value

is maximum at optimum bitumen content Bo.

4.5 STATIC INDIRECT TENSILE STRENGTH TEST

In Indirect Tensile Strength test (ITS), cylindrical specimens are subjected to

compressive loads, which act parallel to the vertical diametral plane by using theMarshall loading equipment. This type of loading produces a relatively uniform tensile

stress, which acts perpendicular to the applied load plane, and the specimen usually fails

by splitting along with the loaded plane. The values of ITS may be used to evaluate the

relative quality of bituminous mixtures in conjunction with laboratory mix design testing

and for estimating the potential for rutting or cracking.

4.5.1 Determination of Indirect Tensile Strength

Specimens prepared with PB 60/70 were tested. Three specimens were tested

from each binder content. The static indirect tensile test was carried out as per ASTM: D-

4123-82(1995).

The split tensile strength of bituminous mixes was determined by applying a

compressive load to Marshall Specimen along the vertical diametrical plane, through two


B3=5%

Bo=5%

Bo=5%




steel strips 12.5 mm wide. The equipment used for the test is shown in Fig 4.2. The load

was applied at a rate of 50.8 mm/min until failure occurred.

Fig 4.7 Load Application in Indirect Tensile Strength Test

Based upon the maximum load carried by a specimen at failure in indirect tensile

strength test, the indirect tensile strength in kPa is calculated from the following equation:

Indirect Tensile Strength (ITS) = 2F/πLD, where F is the applied vertical load (kN), L is

the mean thickness of the test specimen (m); D is the specimen diameter (m).

4.5.2 Results

Results of the indirect tensile strength test on specimens are given in Table 4.5.

Table 4.5 Indirect Tensile Strength Test results Using Conventional Bituminous Mix

% OF BITUMEN

CONTENTI.T.S – N Tensile Stress - N/sqmm

4 2943 0.2952

4.5 3286.35 0.32964

5 7651.8 0.767521

5.5 5395.5 0.541201

6 5199.3 0.521521





6.5 4120.2 0.413281

Fig 4.8 Binder Content Vs Tensile Stress

4.6 CONCLUSION

Marshall Stability test and indirect tensile strength test were used to evaluate

various mechanical properties of bituminous mixes with different types of bitumen.

From Fig 4.2 to 4.6 it can be seen that the maximum values of Marshall Stabilityvalue, voids filled with bitumen, bulk specific gravity and minimum values of percentage

air void ratio and flow value are obtained at 5% binder content.

From fig 4.8 it can be seen that the maximum indirect tensile strength of the

samples tested is obtained at 5% bitumen content.

Thus the optimum bitumen content related to conventional bituminous mixes

made of 60/70 grade was determined as 5% from the Marshall Stability and Indirect

Tensile Stress tests conducted.


Bo=5%




CHAPTER 5

DETERMINATION OF OPTIMUM BLEND OF WASTE PLASTIC COATED

AGGREGATE BITUMINOUS MIX

5.1 INTRODUCTION

Polymer modified bitumen is emerging as one of the most important construction

materials for flexible pavements. Use of plastic waste in the construction of flexible

pavement is gaining importance because of several reasons, which are, the polymer

modified bitumen shows better properties for road construction along with plastic waste

management, otherwise considered to be a pollution menace, can find its use in this

process and this can help solving the problem of pollution because most of the plastic

wastes are non-bio degradable polymers.

Various studies are being carried out to improve the quality of bitumen used in bituminous road construction. One of the results of such studies is to use polymer-

modified bitumen. Use of disposed plastic waste (especially plastic bags) is the need of

the hour. The studies on the thermal behavior and binding property of the molten plastics

promoted a study on the preparation of plastic waste-bitumen blend and its properties to

find the suitability of the blend for road construction.

5.2 POLYMER MODIFIED BITUMEN

In the construction of flexible pavements, bitumen plays the role of binding the

aggregate together by coating over the aggregate. It also helps to improve the strength of

the road. But its resistance towards water is poor. Anti-stripping agents are being used. A

common method to improve the quality of bitumen is by modifying properties of bitumen

by blending with organic synthetic polymers like rubber or plastics. Studies on this

subject are going on both at national and international level. As we are solely





concentrating towards the blending of plastic with the normal bitumen-aggregate mix, we

will explore the basic process of incorporating the plastic in the bituminous mix. This

basic process involves four steps, namely

• Segregation of plastic

• Cleaning of plastic

• Shredding of plastic

• Collection of the shredded plastic

The Segregation process involves the collection of plastic wastes from various sources

and separating then as per the thickness criteria (maximum thickness of 60μ). After the

segregation process, the plastic wastes collected must go through a cleaning process and

dried properly. Now comes the shredding process, where the plastic wastes will be

shredded or cut into small pieces and different types of shredded plastic wastes are mixedtogether. Now the last step, that is the collection of the shredded plastic, the shredded

pieces are sieved using 2.36 mm IS standard sieve and the portion retained in it is

considered for the experiment.

As far as blending of plastic with the bituminous mix is concerned, there are two

ways of blending the plastic with bituminous mix, which are

1. Wet process.

2. Dry process.

In our case we are implementing Wet Process to blend the plastic directly with the

heated bitumen.

5.3 DRY PROCESS:

In a nutshell, Dry Process can be defined as the process of mixing plastic with

aggregate to obtain the plastic blended bituminous mix. The plastic fragments used are

mainly the fragments of the disposed carry bags, films, cups etc, with a maximum

thickness of 60μ, as discussed above

The optimum bitumen content obtained from the test results was 5%. The

polymer modified bitumen specimens were prepared by partial replacement of the

bitumen content on optimum bitumen content with 4%, 6%, 8%, 10% ….





Minimum three specimens were tested in each case and the average of the test

results were taken for the analysis.

Procedure:

• The bitumen is heated to a temperature of around 120°C to 140°C

• The measured weight of waste plastic scraps are directly mixed with the heated

aggregate.

• The plastic fragments get melted when it comes in contact with the heated

aggregate and a plastic coated aggregate mix is obtained

• Now, the heated bitumen is poured over the aggregate-plastic mix. Mixing is done

thoroughly and carefully so that a homogeneous mix is obtained.

• The mixture was heated to the temperature of 1500C

• The mixture was poured in to the pre-heated cylindrical moulds of 10cm diameter

and applied 50 blows on each side using Marshall hammer

• Cylindrical moulds with specimens were allowed to cool for 24 hours and then

the specimens were removed from the moulds

5.4 MARSHALL STABILITY TEST

There are two major features of the Marshall method of designing mixes namely,

i) density-void analysis

ii) stability-flow test

5.4.1 Density-Void Analysis

The properties that are of interest include the theoretical specific gravity (G t), the

bulk specific gravity of the mix (Gm), percent air voids (Vv), percent volume of bitumen

(V b), percent void in mixed aggregate (VMA) and percent voids filled with bitumen

(VFB).





Theoretical Specific Gravity (G t )

Theoretical specific gravity Gt is the specific gravity without considering air

voids, and is given by:

Gt=W1+W2+Wp+WbW1G1+W2G2+WbGb+WpGp

where, W1 is the weight of coarse aggregate in the total mix, W2 is the weight of fine

aggregate in the total mix, W b and W p is the weight of bitumen and plastic respectively in

the total mix, G1 is the apparent specific gravity of coarse aggregate, G2 is the apparent

specific gravity of fine aggregate and G b and G p is the apparent specific gravity of bitumen

and plastic respectively.

Bulk Specific Gravity (G m )

The bulk specific gravity or the actual specific gravity of the mix Gm is the

specific gravity considering air voids and is found out by:

Gm= WmWm-Ww

Where, Wm is the weight of mix in air, Ww is the weight of mix in water.

Air Voids Percent (V v )

Air voids Vv is the percent of air voids by volume in the specimen and is given as

Vv= Gt-Gm100Gt

Where, Gt is the theoretical specific gravity of the mix and G m is the bulk or actual

specific gravity of the mix.

Percent Volume of Bitumen (V b )

The volume of bitumen V b is the percent of volume of bitumen to the total volume

and is given by:

Vb= WbGb+WpGpW1+W2+Wb+WpGpGb





where, W1 is the weight of coarse aggregate in the total mix, W2 is the weight of

fine aggregate in the total mix, W b and W p is the weight of bitumen and plastic

respectively in the total mix, G1 is the apparent specific gravity of coarse aggregate, G2 is

the apparent specific gravity of fine aggregate and G b and G p is the apparent specific gravity

of bitumen and plastic respectively..

Voids In Mineral Aggregate (VMA)

Voids in mineral aggregate VMA is the volume of voids in the aggregates, and is

the sum of air voids and volume of bitumen, and is calculated from

VMA = V v + V b

where, Vv is the percent air voids in the mix and V b is percent bitumen content in the mix.

Voids Filled With Bitumen (VFB)

Voids filled with bitumen VFB is the voids in the mineral aggregate frame work

filled with the bitumen, and is calculated as:

VFB= Vb×100VMA

Where, V b is percent bitumen content in the mix and VMA is the percent voids in the

mineral aggregate.

5.4.2 Marshall Stability and Flow

Specimens were prepared as per standards. Prior to the conduct of Marshall Test,

specimens were immersed in water at 60ºC for 40 min. The test was performed with

varying binder contents and the Marshall stability and flow values were determined.

It is possible while making the specimen that the thickness slightly varies from

the standard specification of 63.5 mm. Therefore, measured stability values are correctedto those which would have been obtained if the specimens had been exactly 63.5 mm by

multiplying with appropriated correlation factors.

Results





The mechanical properties of the bituminous mixtures containing polymer

modified bitumen and plain bitumen such as stability, flow, bulk specific gravity, air

voids, voids in mineral aggregate and voids filled with bitumen are presented in Table

5.1.

Table 5.1 Marshall Stability Test results Using Plastic Blend Bituminous Mix

% OF

PLASTIC

CONTENT

SP:

NO:

Height-

mm

BULK SP.

GRAVITY

(Gm)

% OF AIR

VOIDS

(Vv)

VOIDS

FILLED

WITH

BITUMEN

(VFB)

MARSHALL

STABILITY

VALUES

(M)-KN

FLOW

VALUES

(δ)- mm

41 65 2.38171 1.885624 72.61506 22.094 3.64

2 65 2.384462 1.772239 73.83083 21.4336 3.55

61 64.5 2.38171 1.892561 72.54197 26.59 3.3

2 65 2.392786 1.436326 77.68407 25.75738 3.24

81 65 2.384462 1.786129 73.67971 27.75984 1.38

2 65.5 2.38171 1.899498 72.46904 27.65831 1.46

10 1 65 2.384462 1.793074 73.60438 19.07309 1.6

2 64 2.392786 1.450264 77.5162 18.63663 2.3

5.4.3 Determination of Optimum Binder Content

Five graphs are plotted with values of bitumen content against the values of

i. Bulk Specific Gravity (Gm)

ii. Marshall Stability (S)

iii. Voids in total mix (Vv)

iv. Flow Value (F)





v. Voids filled with bitumen (VFB %)

Let the bitumen corresponding to maximum bulk specific gravity (Gm) be B 1,

corresponding to maximum Marshall Stability (S) be B2 and that corresponding to

minimum voids ratio (vv) be B3, then the optimum bitumen content for mix design isgiven by Bo = (B1+B2+B3 )/3

The value of flow and VFB values are checked at the optimum bitumen content

Bo and the flow value should be minimum and VFB value should be maximum at

optimum bitumen content Bo. If not it should meet the specified design requirements of

the mix as given by IRC: 29 -1968

Fig 5.1 % Plastic Content Vs Bulk Specific Gravity

From fig 5.1, the % plastic content corresponding to maximum bulk specific

gravity (B1) is obtained as 8%

Fig 5.2 % Plastic Content Vs Marshall Stability Value

From fig 5.2, the % plastic content corresponding to maximum Marshall Stability

value (B2) is obtained as 8%

Fig 5.3 % Plastic Content Vs Flow Value

From fig 5.3, the % plastic content corresponding to minimum Flow Value (B3) is

obtained as 8%

Fig 5.4 % Plastic Content Vs % Air Voids

Fig 5.5 % Plastic Content Vs % VFB


B1= 8%

B3=8%

B2= 8%

B0 = 8%Bo= 8%




From fig 5.4 and 5.5 it can be seen that the flow value is minimum and VFB value

is maximum at optimum plastic content Bo

5.5 STATIC INDIRECT TENSILE STRENGTH TEST

In Indirect Tensile Strength test (ITS), cylindrical specimens are subjected to

compressive loads, which act parallel to the vertical diametral plane by using the

Marshall loading equipment. This type of loading produces a relatively uniform tensile

stress, which acts perpendicular to the applied load plane, and the specimen usually fails

by splitting along with the loaded plane. The values of ITS may be used to evaluate the

relative quality of bituminous mixtures in conjunction with laboratory mix design testing

and for estimating the potential for rutting or cracking.

5.5.1Determination of Indirect Tensile Strength

Plastic blended bituminous specimens prepared were tested. Three specimens

were tested from each binder content. The static indirect tensile test was carried out as per

ASTM: D-4123-82(1995).

Table 5.2 Indirect Tensile Strength results for Plastic Blended Bituminous mix

% OF BITUMEN

CONTENT I.T.S – N Tensile Stress - N/sqmm

4 7749.9 0.777361

6 8142.3 0.816721

8 9338.5 0.936707

10 6375.5 0.6395

Fig 5.6 % Plastic Content Vs ITS

5.6 CONCLUSION


B0 = 8%




Marshall Stability test and indirect tensile strength test were used to evaluate

various mechanical properties of bituminous mixes with different percentage replacement

of bitumen with plastic.

From Fig 5.1 to 5.5 it is clear that the maximum values of Marshall Stabilityvalue, voids filled with bitumen, bulk specific gravity and minimum values of percentage

air void ratio and flow value are obtained at 8% partial replacement of bitumen with

plastic content.

From fig 5.6 it can be seen that the indirect tensile strength of the samples tested

is obtained at 8% partial replacement of bitumen with plastic content.

Thus the optimum partial replacement of bitumen with plastic content for the

mixes made of 60/70 grade was determined as 8% from the Marshall Stability and

Indirect Tensile Stress tests conducted.

CHAPTER 6

SUMMARY AND CONCLUSION

6.1 SUMMARY

Using the test results furnished in the chapter 4 and 5 a comparative study of

conventional bituminous mix and plastic blended bituminous mix is given below in table

6.1 with respect to the Marshall Stability Test results and Indirect Tensile Strength Test

results.

Table 6.1 Comparison of Conventional and Plastic blended mix

PropertiesRequirementsof mix as per

IRC: 29-1968

ConventionalBituminous Mix

(CB)

Plastic blendedBituminous Mix.

(PMB)

Remark

Optimum

Binder Content

3.5% to 7.5% 5% 5% 1. Values are meeting the

requirements.

2. PMB mix was prepared





Fig 6.1 Comparison of Marshall Stability Value

Fig 6.2 Comparison of Indirect Tensile Strength Value

6.2 CONCLUSION

The objectives of the study were to evaluate the performance of polymer modified

bituminous mixes through laboratory investigations. Aggregate and binder tests were

conducted to assess the suitability of the materials used in the study. Various laboratory

tests like Marshall Stability test and indirect tensile test were used to evaluate the

characteristics of bituminous mixes. Based on the laboratory test results, the following

conclusions were drawn.

Various properties of the materials used in the study were tested in the laboratory.

Both aggregate and binder test results have found to meet the specifications.

The optimum bitumen content related to conventional bituminous mixes made of

60/70 grade was determined as 5% from the Marshall Stability and Indirect

Tensile Stress tests conducted

The optimum partial replacement of bitumen with plastic content for the mixes

made of 60/70 grade was determined as 8% from the Marshall Stability and

Indirect Tensile Stress tests conducted

In the indirect tensile strength test, it was obtained that the indirect tensile strength

of bituminous mixes prepared with PMB 40 was higher compared with that of

plain bituminous mixes. .

The Marshall Stability value of the mix can be increased by 43.63 by 8% partial

replacement of bitumen with plastic and indirect tensile strength values an be

increased by 32.67 by 8% partial replacement of bitumen with plastic.

6.3 SCOPE FOR FURTHER STUDY





1. A descriptive test program including fatigue and permanent deformation tests with

varying test temperature, loading conditions, etc need to be conducted to determine the

life of the bituminous mixes and the resistance to plastic deformation.

2. A better comparison of conventional bituminous mix and polymer modified bitumencan be done by performing cost estimation for construction.

Fig 6.3 (a): Samples used for testing

Fig 6.3 (b): Apparatus used for testing





REFERENCES1. Sabina, Tabrez A Khan. (2009), ‘Performance Evaluation of Waste Plastics’,

Indian Institute of Technology Delhi.

2. R. Vasudevan (2005) ‘Utilization of Waste Plastics in Construction of Flexible

Pavements’, Thiagarajar College of Engineering, Madurai – 625 015, Tamil Nadu

– INDIA

3. Dr. M.V.L.R (2009) Anjaneyalu ‘Polymer Modified Bituminous Mixes’, National

Institute of technology Calicut.

4. S.S. Varma ‘Roads from Plastics’, Indian Institute of Technology Delhi

5. Dr. S.K. Khanna and Dr. C.E.G Justo (2001), Eighth edition, ‘Highway

Engineering’.





6. Dr. S.K. Khanna and Dr. C.E.G Justo (2007), Fourth edition, ‘Highway Material

Testing Laboratory Manual’

7. E. J Yoder (2007), ‘Principles of Pavement Design’

7.dry process

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