Prof. T. Pellinen

Lecture 5b – Grading of bituminousmaterials (quality control)

• Reading material & learning objectives: 2-3• Bitumen Grading Systems and list of specifications: 4-16• Selection of bitumen for asphalt mixtures in Finland :17• Conventional Test Methods for Grading: 17-26• PG Grading and Superpave methods:• PG Plus Tests: 39-43• Specifications: US PG Spec and EN Spec: 45• Review questions: 46-47

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Prof. T. Pellinen

Reading Material

• Text book, Cold Regions Engineering,– Chapter 7: Mix Design, 7-2-1 Material selection

• Pages 269- 277

– Chapter 4: Investigation and Testing• Pages 169-173

• www.pavementinteractive.org (Internet)• Materials/Asphalt• Testing/Binder Tests

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Prof. T. Pellinen

Learning objectivesOppimistavoitteet

(must know) (should know) (nice to know)

ScientificKnowledge

Know what is the differencebetween empirical and rheologicaltests

Know why we test the materialwith each test and how does theparameter from the test relatesto the traffic loading

Professionalknowledge

Can list the bitumens gradingsystems and the main tests usedwithin the systemCan list the tests for bitumenCan grade a bitumen whenprovided a list of parametersCan choose the bitumen for theparticular application

Knows how the gradingsystems were developed andknows the direction towardswhich the future development isgoing.Can describe the properties ofthe bitumen using thespecifications.Knows which parameters to testfrom bitumen in order to predictthe possible failure modes ofpavement.

Can tell how the tests aredoneKnows what is the differencebetween the European andAmerican standards (ASTM,AASHTO). Understands thePG grading and MSCR test

Tietää miten Eurooppalaisetstandardit eroavat ASTM jaAASHTO standardeistaPG luokitus ja MSCR testi

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Prof. T. Pellinen

Purchasing of Bitumen

• Need to be able to specify desirablecharacteristics

• “Desirable characteristics” have evolvedover time and with increasingtechnological advances

• Purchasing requires specifications

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Prof. T. Pellinen

Early Specifications

• Lake Asphalts– Appearance– Solubility in carbon disulfide

• Petroleum asphalts (early 1900’s)– Consistency– Chewing– Penetration machine

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Prof. T. Pellinen

Asphalt Grades and Specifications

• Asphalt cements are graded according to thefollowing four systems:– Penetration grading system

• PEN– Viscosity grading system

• AC– Viscosity-after–aging grading system (California)

• AR (aged residue, after RTFO test)– New Superpave Performance Grading (developed 90’s

in the US)• PG

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Prof. T. Pellinen

Why New Grading System wasNeeded?

• Binder modification wasemerging trend due toimprovements in bitumenproperties:– Increases high temperature

viscosity (to reduce rutting)– Increases low temperature

ductility (to reduce fatigue andthermal cracking)

• Difficulties to grade modifiedbinders using conventionalgrading systems:– Non-linear Newtonian behavior

Modifiers used: StyrenButadien Styren (SBS), LowDensity Polyethylene (LDPE),Elvaloy etc.

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Prof. T. Pellinen

Consistency

• Bitumen can vary from solid to semisolid toliquid depending on temperature

• Consistency is the measure of the degree offluidity of the bitumen at any particulartemperature:– Consistency is measured indirectly by either

measuring viscosity or penetration– Direct measurement is the shear (complex) modulus

of the asphalt |G*| which is a function of shear stress(t) and shear strain (g)

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Prof. T. Pellinen

• Important Properties in Construction:– Consistency at a standard temperature.

• viscosity at 60°C and 135°C and penetration 25°C– Ring and Ball Softening point– Specific gravity– Durability (Hardening and aging i.e., effect of heat and air)– Ductility (Fracture properties)– Flash point (Safety)– Solubility (Purity)

• Fraass breaking point is used in countries with very lowwinter temperatures (Finland, Sweden, Norway andCanada)

Measured Properties: Bitumen(for paving grade bitumen)

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Prof. T. Pellinen

List of Bitumen specifications(Finnish and international)

• SFS standardit ja EN standardit (European Committee forStandardization)– PANK (Päällystealan Neuvottelukunta ry) Asfalttinormit ja PANK-

menetelmät– DIN (Deutsche Institut für Normung), Germany– BS (British Standards) and IP (Institute of Petroleum), UK– LCPC (Laboratoire Centrale des Ponts at Chaussées), France

• ASTM (American Society for Testing and Materials), USA• AASHTO (American Association of State Highway Officials), USA• SA (Standards Australia), Australia

– All tough test methods for certain bituminous products in ASTM andAASHTO, SFS-EN standards are very similar, however deviations existand one must be careful to select appropriate standard.

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Prof. T. Pellinen

ASTM D3381: Viscosity Grading

Absolute viscosity at 60°C (max service temperature)Kinematic viscosity at 135°C (mixing temperature)

MAAT > 24°CMAAT < 7°C

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Prof. T. Pellinen

ASTM D946: Penetration Grading

Based on Penetration at 25°C

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Prof. T. Pellinen

PANK Asfalttinormit 2011(Tiebitumien laatuvaatimukset)

Murtumispiste: Fraass breaking point

Ohutkalvokoe: Rolling Thin Film Oven Test13

Prof. T. Pellinen

PANK Asfalttinormit 2011(Pehmeiden tiebitumien laatuvaatimukset)

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Prof. T. Pellinen

Simonen, M. Biofluksattujen bitumien ominaisuudet ja käyttövarastoitavissa pehmeissä asfalttibetonimassoissa. Dipl.työ.2011

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Prof. T. Pellinen

Asphalt Institute Tube Zietfuchs Cross-ArmTubeAsphalt Institute Tube Zietfuchs Cross-ArmTube

• Absolute viscosity ASTM D2171– Vacuum capillary viscometers

• Kinematic viscosity ASTM D2170– Reverse-flow viscometers

Conventional Ways to MeasureBitumen Viscosity

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Prof. T. Pellinen

Penetration(Tunkeuma)

• Distance in tenth of a millimeter that a standard needle penetratesto a sample under standard condition of loading (100 g), time (5seconds), and temperature (e.g., 25°C)

• High value of penetration indicates a softer consistency or higherfluidity

100 g

Initial

Penetration in 0.1 mm

After 5 seconds

100 g

Initial

100 g

Initial

Penetration in 0.1 mm

After 5 seconds

Penetration in 0.1 mm

After 5 seconds

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Prof. T. Pellinen

Ring and Ball Softening Point TR&B(Pehmenemispiste)

• Way to measure empiricalconsistency of bitumen used in theVan der Poel (1954) Nomograph forbinder stiffness |G*| (Developed byShell Oil)– Binder stiffness is dependent of

loading time and temperature– Two binder properties, penetration

and TR&B softening point are needed

Nomograph can be foundfrom text book of Huang:Pavement Analysis andDesign (2nd ed), page 30318

Prof. T. Pellinen

Specific Gravity (tiheys)• Specific gravity of asphalt is defined as the ratio

of the mass of a given volume of asphalt to thatof an equal volume of water at 25°C or 15.6°C

• Specific gravity of asphalt cement variesbetween 0.95-1.05

• Typical value 1.02

• Specific gravity decreases with increasingbitumen temperature

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Prof. T. Pellinen

Durability (kestävyys)• Durability is defined as the property that permits the

pavement material to withstand the detrimental effectsof temperature, air, and moisture

• Durability can be measured from bituminous mixturesand/or binders

• The effect of binder for durability (effect of heat and air)is measured by two tests:– Thin-film oven test ( ASTM D1754)– Rolling thin-film oven test (ASTM D2872).

• Effect of heat and air is determined to simulate theconditions obtained when the bitumen is used tomanufacture hot-mix.

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Prof. T. Pellinen

Thin Film Oven (TFO) Test -ASTM D1754(Ohutkalvokoe)

• In thin-film oven test a filmof asphalt is exposed to anair current at 163°C for fivehours.

• Significant changes in theproperties (for instanceviscosity or penetration) ofthe asphalt after heatingmay indicate poor durability

Rotating Shelf

Pan

Thermometer

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Prof. T. Pellinen

Fan

Air Line

RotatingBottle

Carriage

Rolling Thin Film Oven (RTFO) Test -ASTM D1754 (Ohutkalvokoe pyörivässä sylinterissä)

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Prof. T. Pellinen

Ductility – ASTM D113(Venymä)

Brittle asphaltis susceptibleto cracking

• Elongation beforebreaking when specimenis pulled apart at aspecified speed(5cm/min) andtemperature (25°C)

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Prof. T. Pellinen

Flash Point and Solubility(Leimahduspiste ja liukoisuus)

Thermometer

Cup filledwith

asphaltWand attached

to gas line

Solubility to trichloroethylene,min 99.0%

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Prof. T. Pellinen

Fraass breaking point(Murtumispiste)

• Test that can be used tomeasrue bitumen behaviorat low (up to -30°C)tempeature

• Determines temperature atwhich bitumen reaches acirtical temprature andcracks.– A steel blaque coated with

0,5 mm bitumen is slowlyflexed and released

– Tempeature of the plaque isreduced at 1°C per minuteuntil bitumen cracks

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Prof. T. Pellinen

The grading system is based on climateand expected in-situ performance

PG 64 - 22

PerformanceGrade

Average 7-day maximumpavement temperature

Minimum pavementtemperature

Superpave Performance GradingSystem (developed in SHRP program in the USA in 90s)

Low Temp Grade

High Temp Grade

http://www.tfhrc.gov/pavement/ltpp/product.htm26

Prof. T. Pellinen

Performance Grading Asphalt Binder

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Prof. T. Pellinen

• Based on fundamental material propertiesrelated to pavement performance:– Rutting ® High Temp Grade– Fatigue cracking ® Intermediate Grade– Low-temperature cracking ® Low Temp Grade

• Based on specified property at performancetemperature which will be determined– |G*|/sind > 1 kPa at 70°C (High Temp Grade)

PG Specification

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PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG 82

(Rotational Viscosity) RV

90 90 100 100 100 (110) 100 (110) 110 (110)

(Flash Point) FP

46 52 58 64 70 76 82

46 52 58 64 70 76 82

(ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 %

(Direct Tension) DT

(Bending Beam Rheometer) BBR Physical Hardening

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-34 -40 -46 -10 -16 -22 -28 -34 -40 -46 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -10 -16 -22-28 -34

Avg 7-day Max, oC1-day Min, oC

(PRESSURE AGING VESSEL) PAV

ORIGINAL

> 1.00 kPa

< 5000 kPa

> 2.20 kPa

S < 300 MPa m > 0.300

Report Value> 1.00 %

20 Hours, 2.07 MPa

10 7 4 25 22 19 16 13 10 7 25 22 19 16 13 31 28 25 22 19 16 34 31 28 25 22 19 37 34 31 28 25 40 37 34 31

(Dynamic Shear Rheometer) DSR G* sin d

( Bending Beam Rheometer) BBR “S” Stiffness & “m”- value

-24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24

-24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12-18 -24

(Dynamic Shear Rheometer) DSR G*/sin d

(Dynamic Shear Rheometer) DSR G*/sin d

< 3 Pa.s @ 135 oC

> 230 oC

CEC

Performance Grades

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PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG 82

(Rotational Viscosity) RV

90 90 100 100 100 (110) 100 (110) 110 (110)

(Flash Point) FP

46 52 58 64 70 76 82

46 52 58 64 70 76 82

(ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 %

(Direct Tension) DT

(Bending Beam Rheometer) BBR Physical Hardening

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-34 -40 -46 -10 -16 -22 -28 -34 -40 -46 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -10 -16 -22-28 -34

Avg 7-day Max, oC1-day Min, oC

(PRESSURE AGING VESSEL) PAV

ORIGINAL

< 5000 kPa

> 2.20 kPa

S < 300 MPa m > 0.300

Report Value> 1.00 %

20 Hours, 2.07 MPa

10 7 4 25 22 19 16 13 10 7 25 22 19 16 13 31 28 25 22 19 16 34 31 28 25 22 19 37 34 31 28 25 40 37 34 31

(Dynamic Shear Rheometer) DSR G* sin d

( Bending Beam Rheometer) BBR “S” Stiffness & “m”- value

-24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24

-24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12-18 -24

(Dynamic Shear Rheometer) DSR G*/sin d

(Dynamic Shear Rheometer) DSR G*/sin d

< 3 Pa.s @ 135 oC

> 230 oC

CEC

58 64

Test TemperatureChanges

Spec RequirementRemains Constant

> 1.00 kPa

How the PG Spec Works

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Prof. T. Pellinen

FatigueCrackingRutting

RTFOShort Term AgingNo aging

Construction

[RV] [DSR]

Low TempCracking

[BBR]

[DTT]

PAVLong Term Aging

Summary of Testing for PG Grading

|G*|/sind |G*|sind

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Prof. T. Pellinen

Rotational Viscometer ASTM D4402(Brookfield Thermosel Apparatus)

• Absolute viscosity• For unmodified and

modified asphalt binders

ThermoselEnvironmentalChamber

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Prof. T. Pellinen

DSR (Dynamic Shear Rheometer)(dynaaminen leikkausreometri)

• Control either stress or strain rate• Torque measurement• Measured property:

– shear stiffness |G*| and phase lag dParallel plates

Coaxial cylinders

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Prof. T. Pellinen

Aging Properties for PG grading

• Rolling Thin Film Oven(Short term aging STA)– Simulates aging from hot

mixing and construction

• Pressure Aging Vessel(Long-term aging LTA)– Simulates aging of an

asphalt binder for 7 to 10years

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Prof. T. Pellinen

CoolingSystem

Fluid BathLoading

Ram

Bending Beam Rheometer (BBR)

Air Bearing

Load Cell

Deflection Transducer

Fluid Bath

ComputerAir Bearing

Load Cell

Deflection Transducer

Fluid Bath

Computer

Measured property:Creep stiffness S(t)and Slope m

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Prof. T. Pellinen Courtesy of FHWA

Direct Tension Test (DTT)

[DTT][DTT]

Measured property:Tensile strain at failure

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Prof. T. Pellinen

Summary of How to UsePG Specification

• Determine– 7-day max pavement temperature at a depth of 20

mm below the pavement surface:– 1-day minimum pavement temperature

• Use specification tables to select testtemperatures– Determine asphalt cement properties (lab tests) and

compare to specification limits

• High temperature is adjusted (grade pumping)for slow traffic

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Prof. T. Pellinen

“PG Plus” Tests• Original PG specification was based on

study of neat (nonmodified binders)– Linear behavior and not stress sensitive

• Use of modified binders has growntremendously– Nonlinear behavior and stress sensitive

• PG grading AASHTO M 320 alone mynot always predicted performance– Grade pumping to increasing rutting

resistance my not be adequate– Recovery of modified binders not

adequately captured• Most states begun requiring additional

empirical tests, referred as “PG Plus”tests– Tests are not standard across states-

difficult to suppliers

Elastic Recovery Test

Danny Gierhart, Asphalt Institute, 201138

Prof. T. Pellinen

PG Grading alones does not alwayspredict performance

Danny Gierhart, Asphalt Institute, 2011 39

Prof. T. Pellinen

Multiple Stress Creep Recovery(MSCR) Test for modified binders

• Allows performance gradebinder spec that is blind tomodification type

• Can relate polymer modifiedbinders potential ruttingperformance to in serviceperformance

• New rutting parameters– Non-recoverable creep

compliance Jnr [1/kPa]– Recovery [%] Creep and recovery – specimen

is subjected to a constant load fora fixed time period and thenallowed to relax (recover) a zeroload for a a fixed time 40

Prof. T. Pellinen

Multiple Stress Creep Recovery(MSCR) Test for modified binders

Reducing Jnr by half typically reduced rutting by half

Danny Gierhart, Asphalt Institute, 2011 41

Prof. T. Pellinen

New PG grading system (MSCR)

• Environmental grade plus trafficdesignation i.e. PG 64-22E.

• Four traffic levels.

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Prof. T. Pellinen

US PG Specs• PG-grading (AASHTO M320-10/ASTM D6373 -

07e1):– PG-luokan määrittäminen (G*/sinδ and G*sinδ):

• AASHTO R29-08: Grading or Verifying the Performance Grade(PG) of an Asphalt Binder

• ASTM D7643 - 10: Standard Practice for Determining theContinuous Grading Temperatures and Continuous Grades for PGGraded Asphalt Binders

– Multiple Stress Creep Recovery (MSCR) -test:• AASHTO TP 70-12: Standard Method of Test for Multiple Stress

Creep Recovery (MSCR) Test of Asphalt Binder Using a DynamicShear Rheometer (DSR)

• ASTM D7405 - 10a: Standard Test Method for Multiple StressCreep and Recovery (MSCR) of Asphalt Binder Using a DynamicShear Rheometer

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Prof. T. Pellinen

Review Questions• List bitumen grading systems• What is the test the viscosity grading system is based on?• Why PG-grading was developed in the US?• Should we use PG grading also in Europe?• What pavement distress penetration is describing?• How do we know if bitumen ages too much on the road?• If asphalt mixture is shoving, should contractor change the bitumen

type or put less bitumen to asphalt mixture?• If bitumen cools down below 60 °C during asphalt construction,

what consequences it may have?• While fabricating asphalt mixture, is it more convenient to measure

amount of bitumen by mass or by volume?

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Prof. T. Pellinen

Review Questions

Ominaisuus Yksikkö TestiarvotViskositeetti 60 °CTunkeuma, 25°C, 100 g, 5s

Poise0,1 mm

568128

Viskositeetti 135 °CLeimahduspiste, Cleveland Open cup

cSt°C

123190

The deep rutting occured on the constructed road just after the trafficing. Thefirst assumption was that the bitumen used may have not been according to themix design. The samples of asphalt were collected from the road and bitumenwas recovered from them and evaluated with a few chosen tests. The resultsare in the table.

The mix design assumed the use of bitumen 70/100. Did the contractor usethe specified bitumen?If not, what grade of bitumen was used? Support your answer.

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