asphalt rubber binder and mix design - rubber...

Asphalt Rubber Binder and Asphalt Rubber Binder and Mix DesignMix Design

Barry Takallou, Barry Takallou, Ph.DPh.D, P.E., P.E.

APWA

Columbus, Ohio

September 15, 2009

Asphalt Rubber Binder and Mix Design

Presentation OutlinePresentation Outline

•• Asphalt Rubber BinderAsphalt Rubber Binder–– ComponentsComponents–– PropertiesProperties–– Quality ControlQuality Control

•• Mix Design Mix Design ConsiderationsConsiderations–– Gap Graded or SMAGap Graded or SMA


COMPONENTSCOMPONENTS

•• Asphalt Cement (Bitumen)Asphalt Cement (Bitumen)•• Crumb Rubber ModifierCrumb Rubber Modifier•• AdditivesAdditives


Asphalt CementAsphalt Cement•• Variety of Grades and DesignationsVariety of Grades and Designations

–– PG PG –– Performance GradesPerformance Grades–– AR AR –– ARAR--40004000–– AC AC –– ACAC--10, AC10, AC--2020–– PenetrationPenetration

•• Softer Grades Typically Used in Asphalt Softer Grades Typically Used in Asphalt RubberRubber


ASPHALT CEMENTSASPHALT CEMENTS

USED FOR ASPHALT RUBBER USED FOR ASPHALT RUBBER BINDERBINDER

Type 1: Hot ClimateType 1: Hot Climate

PG 64PG 64--16 (AC16 (AC--20)20)Type 2: Moderate ClimateType 2: Moderate Climate

PG 58PG 58--22 (AC22 (AC--10) 10) Type 3: Cold ClimateType 3: Cold Climate

PG 52PG 52--28 (AC28 (AC--5)5)


Crumb RubberCrumb Rubber•• Derived from scrap tires and other Derived from scrap tires and other

waste rubber productswaste rubber products•• Comes in variety of grades and Comes in variety of grades and

designationsdesignations–– Sieve sizeSieve size–– Material origin or sourceMaterial origin or source

•• Mesh size refers to first sieve with 5 Mesh size refers to first sieve with 5 to 10% retainedto 10% retained


Crumb RubberCrumb Rubber•• Usually identified by 3 typesUsually identified by 3 types

–– Type 1 Type 1 –– (Grade A) (Grade A) –– Coarse Coarse –– 10 mesh10 mesh•• Used for spray applications like chip sealingUsed for spray applications like chip sealing

–– Type 2 Type 2 –– (Grade B) (Grade B) –– 14 to 20 mesh14 to 20 mesh•• Used for Used for hotmixhotmix and spray applications in and spray applications in

moderate and cold climatesmoderate and cold climates

–– Type 3 Type 3 –– 30 mesh30 mesh•• Used for Used for hotmixhotmix designs in extreme cold climatesdesigns in extreme cold climates


Crumb RubberCrumb Rubber•• Variety of packaging availableVariety of packaging available

–– 50 lb paper sacks50 lb paper sacks–– Up to 1 ton Up to 1 ton supersackssupersacks

•• Major issue with MoistureMajor issue with Moisture–– Typically upper limit of 0.75%Typically upper limit of 0.75%–– Can cause foaming and safety issuesCan cause foaming and safety issues


AdditivesAdditives•• Used to aid or produce desirable propertiesUsed to aid or produce desirable properties•• Extender OilsExtender Oils

–– Provides aromatics to assist crumb rubber interaction Provides aromatics to assist crumb rubber interaction with asphalt cementwith asphalt cement

•• AntiAnti--strip agentsstrip agents–– Increase/improve adhesionIncrease/improve adhesion

•• High Natural RubberHigh Natural Rubber–– Improve adhesion and flexibilityImprove adhesion and flexibility

•• PolymersPolymers


PropertiesProperties

•• ReactionsReactions•• Specification Specification

TestingTesting•• Asphalt Rubber Asphalt Rubber

Binder Design Binder Design ProfileProfile


Reactions between ComponentsReactions between Components

•• Dependant on:Dependant on:–– TimeTime–– TemperatureTemperature–– Component interaction based on Component interaction based on

chemical makeupchemical makeup


Specification TestingSpecification Testing•• Apparent ViscosityApparent Viscosity•• PenetrationPenetration•• Softening PointSoftening Point•• DuctilityDuctility•• ResilienceResilience


Apparent ViscosityApparent Viscosity•• Rotational ViscometerRotational Viscometer

–– BrookefieldBrookefield ViscometerViscometer–– HaakeHaake ViscometerViscometer–– Presented in Presented in centiposecentipose ((cPcP) )

or Pascal Seconds (Paor Pascal Seconds (Pa--s)s)

•• Monitors fluid consistencyMonitors fluid consistency–– Aggregate coatingAggregate coating–– PumpabilityPumpability

•• BrookefieldBrookefield sometimes sometimes used for acceptance used for acceptance –– need calibrationneed calibration


Field VerificationField Verification


PenetrationPenetration ASTM D 5 AASHTO T 49ASTM D 5 AASHTO T 49

•• Measurement by Measurement by PenetrometerPenetrometer–– Results in tenths of millimeter Results in tenths of millimeter

unitsunits

•• Needle at 39.2Needle at 39.2°°F and F and 77.077.0°°FF

•• Cone penetration used with Cone penetration used with larger size crumb rubber larger size crumb rubber (10 mesh or larger)(10 mesh or larger)


Softening PointSoftening Point ASTM D36 AASHTO T 53ASTM D36 AASHTO T 53

•• Ring and Ball MethodRing and Ball Method•• Presented as Presented as °°F or F or °°CC•• Indicator of material Indicator of material

stiffnessstiffness•• Shows tendency of Shows tendency of

material to flow at material to flow at elevated elevated temperaturestemperatures


DuctilityDuctility ASTM D 5ASTM D 5 AASHTO T 49AASHTO T 49

•• Pulls sample apart at specific ratePulls sample apart at specific rate•• Measure of tensile propertiesMeasure of tensile properties•• Not considered reliable for asphalt rubberNot considered reliable for asphalt rubber


ResilienceResilience ASTM D5329ASTM D5329

•• Measures elastic Measures elastic properties of binderproperties of binder

•• Expressed as Expressed as percentage of percentage of reboundrebound

•• Considered reliable Considered reliable and importantand important


Asphalt Rubber Binder Design ProfileAsphalt Rubber Binder Design Profile

•• Evaluate compatibility between proposed Evaluate compatibility between proposed componentscomponents

•• Provide guidance to field for proportioningProvide guidance to field for proportioning•• Evaluate stability of binder over timeEvaluate stability of binder over time


Minutes of Reaction SpecifiedTest Performed 60 90 240 360 1440 Limits

Viscosity, Haake at 177°C, Pa-s Centipoise cP

2.72700

2.82800

2.82800

2.82800

2.02000

1.5-4.01500-4000

Resilience at 25°C, % Rebound(ASTM D3407)

34 36 32 30 Minimum

Ring & Ball Softening Point, °F(ASTM D36)

150.0 150.5 152.5 154.5 145.0 135 Minimum

Needle Penetration at 4°C, 200g, 60sec., 1/10mm (ASTM D5)

22 24 26 10 Minimum

Typical Asphalt Rubber Binder Design ResultsTypical Asphalt Rubber Binder Design Results


Minutes of Reaction SpecifiedTest Performed 60 90 240 360 1440 Limits

Viscosity, Haake at 177°C, Pa-s Centipoise cP

3.63600

2.42400

1.81800

1.51500

0.85850

1.5-4.01500-4000

Resilience at 25°C, % Rebound(ASTM D3407)

38 28 20 30 Minimum

Ring & Ball Softening Point, °F(ASTM D36)

149.0 141.0 138.0 136.5 134.5 135 Minimum

Needle Penetration at 4°C, 200g, 60sec., 1/10mm (ASTM D5)

18 26 34 10 Minimum

Binder Design Showing Long Term InstabilityBinder Design Showing Long Term Instability


Quality ControlQuality Control•• PrePre--job testing sets standard for job testing sets standard for

comparison to field testingcomparison to field testing•• Establish target viscosity for fieldEstablish target viscosity for field•• Significant fluctuations in field should be Significant fluctuations in field should be

investigatedinvestigated


Quality ControlQuality Control•• Sample reheating has been shown to Sample reheating has been shown to

affect resultsaffect results•• Typically viscosity is lowered, resilience Typically viscosity is lowered, resilience

and softening point decreased, and softening point decreased, penetration increasespenetration increases

•• Prepare all test samples at the same timePrepare all test samples at the same time

Asphalt Rubber Mixture Asphalt Rubber Mixture DesignDesign

Gap Graded or SMAGap Graded or SMA


Gap Graded : PurposeGap Graded : Purpose

•• Highly flexible liftHighly flexible lift•• High quality structural liftHigh quality structural lift•• Typically nominal 2 inch liftTypically nominal 2 inch lift


Gap Graded : GradationGap Graded : GradationSieve Size Percent Passing

Without admixture¾” 100½” 80-1003/8” 65-80#4 28-42#8 14-22

#200 0-2.5


Gap Graded : Crushed Faces Gap Graded : Crushed Faces

•• Minimum 95% Single Crushed FacesMinimum 95% Single Crushed Faces

•• To insure good particle interlockTo insure good particle interlock


Mix Design StepsMix Design Steps•• Prepare AggregatePrepare Aggregate•• Determine aggregate specific gravitiesDetermine aggregate specific gravities•• Determine maximum theoretical specific Determine maximum theoretical specific

gravitygravity•• Compact mix, determine optimum binder Compact mix, determine optimum binder

contentcontent•• Check mix Check mix volumtericsvolumterics


Gap Graded : DesignGap Graded : Design

•• Determine the maximum theoretical Determine the maximum theoretical specific gravity (Rice test)specific gravity (Rice test)–– Pay extra in separating the aggregatePay extra in separating the aggregate–– High binder content and film thicknessHigh binder content and film thickness



•• Compact with Marshall hammer at three Compact with Marshall hammer at three binder contentsbinder contents

•• Typically 6.5, 7.5, 8.5 or 6.0, 7.0, 8.0 Typically 6.5, 7.5, 8.5 or 6.0, 7.0, 8.0 depending on aggregate sourcedepending on aggregate source

•• Mix at 325 Mix at 325 °°FF•• Compact at 300 Compact at 300 °°FF



•• Check Check VolumetricsVolumetrics, select optimum binder , select optimum binder content.content.

•• Minimum VMA 17.0%Minimum VMA 17.0%•• Effective Voids 4.0 Effective Voids 4.0 -- 6.0%6.0%


Gap Graded : Typical DesignGap Graded : Typical Design

Typical binder content 6.5Typical binder content 6.5--8.5% by weight 8.5% by weight of the mix depending on aggregate source of the mix depending on aggregate source

and gradationand gradation


Questions?Questions?

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