Performance Evaluation of Polymer Modified Asphalt Mix

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    ABSTRACTAsphalt binder whose properties are modified by the addition of a polymer is

    Polymer Modified asphalt.

    Polymer is combination of a large number of similar small molecules or monomers

    into large molecules. Polymers can be divided into two; Natural polymers and Synthetic

    polymers. Natural polymers occur naturally in nature. Examples include hair rubber

    diamonds and sulphur. Synthetic polymers are polymers that have been manufactured in a

    chemical process to combine particular molecules in a way that would not occur naturally.

    !he synthetic polymers are used in modifying asphalt. !he various polymers used to

    modify asphalt include !hermoplastic "ubbers Styrene #utadiene Styrene Ethylene $inyl

    Acetate Amorphous Polyalphaolefin %ellulose fiber Polyolefin #ituminous cellulose

    fiber etc.

    !he polymer additives do not chemically combine or change the chemical nature of

    the asphalt being modified apart from being present in and throughout the asphalt. !he way

    the additive&polymer usually influences the asphalt characteristics is by dissolving into

    certain component fractions of the asphalt itself spreading out its long chain polymer

    molecules to create an inter'connecting matrix of the polymer through the asphalt. (t is this

    matrix of the long chain molecules of the added polymer that modifies the physical

    properties of the bitumen. !he improved properties of the asphalt include lesser stiffness

    greater wor)ability better strength coating capabilities etc.

    !he polymers changes the physical nature of asphalt and modifies the physical

    properties of the asphalt li)e softening point and brittleness of the asphalt. Elastic

    recovery&ductility is also found to be improved. !his in turn will alter the properties of the

    aggregate'bitumen mixture in which the modified bitumen is used. Pavement with polymer

    modification exhibits greater resistance to rutting and thermal crac)ing and decreased

    fatigue damage stripping and temperature susceptibility. Polymer modified binders have

    been used with success at locations of high stress such as intersections of busy streets

    airports vehicle weigh stations and race trac)s.

    !his report aims in explaining the influence of polymer modified asphalt on rutting

    and stripping of hot mix asphalt by reviewing various studies conducted in the past.

    CONTENTS

    *.(N!"+,-%!(+N *

    *.*P+/ME" M+,(0(E, ASP1A! *

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    *.2"-!!(N3 (N ASP1A! PA$EMEN!S 2*.4 S!"(PP(N3 (N ASP1A! PA$EMEN!S 4

    2."-!!(N3 "ES(S!AN%E +0 P+/ME" M+,(0(E, ASP1A! M(5!-"ES 62.* (N!"+,-%!(+N 6

    2.2 E5PE"(MEN!A S!-,/ %+N,-%!E, #/ S-"E//A !A/0-" E!. A (N 2778

    8

    2.2.* MA!E"(AS 8

    2.2.2,E!E"M(NA!(+N +0 +P!(M-M ASP1A! %+N!EN! 9

    2.2.4 PE"0+"MAN%E !ES!S :

    2.2.4.* (N,("E%! !ENS(E S!"EN3!1 !ES! :

    2.2.4.2 (N,("E%! !ENS(E !ES! *7

    2.2.4.4 S!A!(% %"EEP !ES! *4

    2.2.4.6 "EPEA!E, %"EEP !ES! *8

    2.2.4.8 %P% "-!!(N3 !ES! *9

    2.2.6 S-MMA"/ *

    4. S!"(PP(N3 "ES(S!AN%E +0 P+/ME" M+,(0(E, ASP1A! M(5 2*4.* (N!"+,-%!(+N 2*

    4.2 E5PE"(MEN!A S!-,/ %+N,-%!E, #/ %A3"( 3+"AS!M , *==6 ? "ES-!S 2

    4.2.6.2 M+,(0(E, +!!MAN !ES! >AAS1!+ ! 2:4? "ES-!S 44

    4.2.8 S-MMA"/ 4=

    6. %+N%-S(+NS 4:

    2

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    "E0E"EN%ES 4

    1. INTRODUCTION

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    1.1 POLYMER MODIFIED ASPHALT

    Asphalt binder whose properties are modified by the addition of a polymer is

    Polymer Modified asphalt.

    Polymer is combination of a large number of similar small molecules or monomers

    into large molecules. !he polymer will have different properties than the monomer. !here

    are a large number of naturally occurring polymers; these can be organic or mineral

    substances. Such natural examples of polymers include hair rubber diamonds and sulphur.

    Asphalt can also be regarded as a polymer because of the long'chain nature of some of the

    organic molecules that are the constituent parts of asphalt. Synthetic polymers are polymers

    that have been manufactured in a chemical process to combine particular molecules in a

    way that would not occur naturally. !he synthetic polymers are used in modifying asphalt.

    !he various polymers used to modify asphalt include !hermoplastic "ubbers Styrene

    #utadiene Styrene Ethylene $inyl Acetate Amorphous Polyalphaolefin %ellulose fiber

    Polyolefin #ituminous cellulose fiber etc.

    !he polymer additives do not chemically combine or change the chemical nature of

    the asphalt being modified apart from being present in and throughout the asphalt. !he way

    the additive&polymer usually influences the asphalt characteristics is by dissolving into

    certain component fractions of the asphalt itself spreading out its long chain polymer

    molecules to create an inter'connecting matrix of the polymer through the asphalt. (t is this

    matrix of the long chain molecules of the added polymer that modifies the physicalproperties of the bitumen. !he improved properties of the asphalt include lesser stiffness

    greater wor)ability better strength coating capabilities etc. !he polymers changes the

    physical nature of asphalt and modifies the physical properties of the asphalt li)e softening

    point and brittleness of the asphalt. Elastic recovery&ductility is also found to be improved.

    !his in turn will alter the properties of the aggregate'bitumen mixture in which the

    modified asphalt is used. Pavement with polymer modification exhibits greater resistance to

    rutting and thermal crac)ing and decreased fatigue damage stripping and temperature

    susceptibility. Polymer modified binders have been used with success at locations of high

    stress such as intersections of busy streets airports vehicle weigh stations and race trac)s.!his report aims in explaining the influence of polymer modified asphalt on rutting

    and stripping of hot mix asphalt by reviewing various studies conducted in the past.

    1.2 RUTTING IN ASPHALT PAVEMENTS

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    "utting is surface depression in the wheel path. Pavement uplift >shearing? may

    occur along the sides of the rut. "uts are particularly evident after a rain when they are

    filled with water. !here are two basic types of rutting@ mix rutting and subgrade rutting.

    Mix rutting occurs when the subgrade does not rut yet the pavement surface exhibits wheel

    path depressions as a result of compaction&mix design problems. Subgrade rutting occurs

    when the subgrade exhibits wheel path depressions due to loading. (n this case the

    pavement settles into the subgrade ruts causing surface depressions in the wheel path. "uts

    filled with water can cause vehicle hydroplaning can be haardous because ruts tend to pull

    a vehicle towards the rut path as it is steered across the rut.

    !he reason for rutting is permanent deformation in any of pavementBs layers or

    subgrade usually caused by consolidation or lateral movement of the materials due to traffic

    loading. Specific causes of rutting can be@

    (nsufficient compaction of 1MA layers during construction. (f it is not

    compacted enough initially 1MA pavement may continue to densify under

    traffic loads.

    Subgrade rutting >e.g. as a result of inadeCuate pavement structure?

    (mproper mix design or manufacture >e.g. excessively high asphalt content

    excessive mineral filler insufficient amount of angular aggregate particles?

    Fig.1.1 Rutting in as!a"t a#$%$nts

    S&u'($)***.t$!a%a(&unt+u,"i(*&'-s.(&%

    1. STRIPPING IN ASPHALT PAVEMENTS

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    !he loss of bond between aggregates and asphalt binder that typically begins at the

    bottom of the 1MA layer and progresses upward is called stripping. Dhen stripping begins

    at the surface and progresses downward it is usually called raveling.

    Stripping decreases structural support and it also leads to rutting

    shoving&corrugations raveling or crac)ing >alligatorand longitudinal?.#ottom'up stripping

    is very difficult to recognie because it manifests itself on the pavement surface as other

    forms of distress including rutting shoving&corrugations raveling or crac)ing. !ypically a

    core must be ta)en to positively identify stripping as a pavement distress. !he reasons for

    stripping are

    Poor aggregate surface chemistry

    Dater in the 1MA causingmoisture damage

    +verlays over an existing open'graded surface course. !hese overlays will tend

    to strip.

    Fig.1.2 St'iing in as!a"t a#$%$nts

    S&u'($)***.t$!a%a(&unt+u,"i(*&'-s.(&%

    2.RUTTING RESISTANCE OF POLYMER MODIFIED ASPHALT MI/TURES

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    http://training.ce.washington.edu/wsdot/modules/09_pavement_evaluation/09-7_body.htm#ravelinghttp://training.ce.washington.edu/wsdot/modules/09_pavement_evaluation/09-7_body.htm#ruttinghttp://training.ce.washington.edu/wsdot/modules/09_pavement_evaluation/09-7_body.htm#corrugationhttp://training.ce.washington.edu/wsdot/modules/09_pavement_evaluation/09-7_body.htm#ravelinghttp://training.ce.washington.edu/wsdot/modules/09_pavement_eval