H. BahiaThe University of Wisconsin-Madison

Advancements in Characterization of Modified Bitumens

Lecture Outline • Targets of bitumen modification• Types of bitumen modifications• Traditional methods of testing PMBs• New methods for evaluating modified

bitumens: –Production and construction –Performance related

• Future trends

The Targets of Modification 1- Temperature Sensitivity

Stiff

ness

, G*

Temperature

ThermalCracking

Fatigue Cracking Rutting

Mixing &Construction

Ideal (modified) bitumen

Typical bitumen

Targets of Modification2- Better Failure Envelop

Log Stress

log Strain

Temp.

Modified bitumen Unmodified

bitumen

ModificationStronger,More Ductile

Enhanced Performance of HMA by Use of Polymer Modification

(H. Von Quintus – AMAP Meeting 2/2004

80 % less Cracking

Enhanced Performance of HMA by Use of Polymer Modification

(H. Von Quintus – AMAP Meeting 2/2004

75% less Rutting

Target Distresses that would justify modifiers- 52 Agencies • Rutting 39/52

• Low temperature cracking 28/52

• Fatigue Cracking 21/52

• Aging 14/52

• Moisture Damage 14/52

Identification of Asphalt Modifiers

Modifier Reference Terrel

and Epps,

1989

Romine et al.,

1991

Peterson

1993

Moratzai Moulthrop

1993

McGennis

1995

Isacsson & Lu

1995

Banasiak and

Geistlinger

1996

1.Thermoplastic P. X X X X X X X 2.Thermoset P. X X X X X X X 3.Fillers/Reinf. 4.Agents/Extenders

X X

X X X

X X X X

5.Adhesion Prom. X X X X X X 6.Catalysts X X X X X X 7.Aging Inhibitors X X X X X X X 8.Others X X X X

Total number - - 46 82* 48 31 62 *(27 ASA): Antistripping Additives

Asphalt Modification Variables

• With additives–Monomer types and combinations–Molecular architecture–Amount used–Method of mixing with asphalt–Third component additives

• Without additives–Oxidation (process)

• Multi grade –Acids (catalysts)

Modifiers in Bitumen -Microscopic Observations

Neat

Oxidized

PE – No SatbilizerEVA

SBS

SBR

Modifiers Most Commonly UsedHighway Agencies in U.S

Generic Type Total No. of Users

• ELASTOMERIC POLYMRES 69 (54%)

• PLASTOMERIC POLYMERS 13 (10%)

• MINERAL FILLERS 13 (10%)• ANTI-OXIDANTS 13 (10%)• HYDROCARBONS 12 ( 9%)• PROCESS-BASED 8 ( 7%)

Modifiers Most Commonly UsedPolymer Modifiers -1998

1. POLYMERS - ELASTOMERSStyrene Butadiene Styrene (SBS) 28• Styrene Butadiene Rubber Latex (SBR)

17• Styrene Butadiene (SB) 16• Styrene Isoprene Styrene (SIS) 1• Styrene Ethylene Butylene Styrene (SEBS) 1• Polyisoprene (natural and synthetic) 1

2004 Survey in USA By AMAP – Mr. John Casola

Specifications & Tests of Modified Bitumen / First Generation

• AASHTO-AGC-ARTBA-~ 1990- Task Force 31Polymer Modified Asphalts–Table 1 - Styrene Block Copolymers–Table 2 - Styrene Butadiene Rubber

Latexes or Neoprene Latex–Table 3 - Ethylene Vinyl Acetate or

Polyethylene

Pre- PG grading Specifications• Task Force 31: Polymer Modified Asphalts- Table 2 • Styrene Butadiene Rubber Latexes or Neoprene Latex

2-A 2-B 2-CPenetration, 77 F, 100 g, 5 sec min 100 70 80Viscosity, 140 F, Poises min 800 1600 1600Viscosity, 275 F, cSt max 2000 2000 2000Ductility, 39.2, 5 cpm, cm min 50 50 25

Flash Point, F min 450 450 450Solubility, % min 99.0 99.0 99.0

Toughness, 77 F, 20 ipm, in-lbs min 75 110 110Tenacity, 77 F, 20 ipm, in-lbs min 50 75 75

RTFOT or TFOT Residue:Viscosity, 140 F, Poises max 4000 8000 8000Ductility Retention, 39.2 F, 5cpm, cm min 25 25 8Toughness, 77 F, 20 ipm, in-lbs min - - 110Tenacity, 77 F, 20 ipm, in-lbs min - - 75

Traditional Tests for Modified Asphalts – Isacsson and Lu

• An index of energy to failure used to detect modifiers and assess their contribution to toughness.

• A hemispherical head is inserted in an asphalt container and thenpulled out. The area under the load deformation curve is dividedinto an initial peak area and a terminal tenacity area. The sum is the toughness.

• Elastomeric modifiers could have a significant effect particularly ifthey are cross linked.

Not a standard

Toughness and Tenacity @ 25°C

• An index of the capability for elastic recovery.• Measured using the conventional ductility set up but sample is

stretched and then cut to measure recovery of cut ends. • Method has been modified several times and is run using sliding

plate rheometer, ARRB Elastometer, Consistometer, and torsionalloading set-up.

• One of the most widely used to determine if modified binderincludes elastomers. Used in North America, Australia and Europe.

Not a Standard

Elastic Recovery @ 25°C

Tensile (extensional) Properties

Elastic Recovery USA Ductility & Australian Elastometer

Toughness and Tenacity

1993- SHRP Performance-Grading Does it apply for PMBs?

PG 58 PG 64 PG 70 Performance Grade

-10 -20 -30 -40 -10 -20 -30 -40 -10 -20 -30 Average 7-day Maximum Pavement Design Temperature, C (a) < 58 < 64 < 70Minimum Pavement Design Temperature, C >-10 >-20 >-30 >-40 >-10 >-20 >-30 >-40 >-10 >-20 >-30

Original Binder Flash Point, AASHTO T48, minimum, C 230 Viscosity, ASTM D4402 (Brookfield):

Max, 2 Pa-s (2000 cSt)Test Temp, C 165

Dynamic Shear, SHRP B-003:G*/sin delta, min 1.0 kPa (0.145 psi) Test Temp @ 10 rad/s, C 58 64 70

Rolling Thin Film Oven Test (AASHTO T240, ASTM D2872) Residue Mass Loss, max, % 0.3 Dynamic Shear, SHRP B-003:

G*/sin delta, min 2.0 kPa (0.290 psi) Test Temp @ 10 rad/s, C 58 64 70

PAV Aging Temperature, C 100 100 100 Dynamic Shear, SHRP B-003:

G* sin delta, max, 3000 kPa (435 psi) Test Temp @ 10 rad/s, C 25 20 15 10 30 25 20 15 40 35 30

Creep Stiffness, SHRP B-002 (b):S, max, 2 E05 kPa, (29000 psi)m-value, min, 0.35Test Temp @ 60 s, C 0 -10 -20 -30 0 -10 -20 -30 0 -10 -20

Direct Tension, SHRP B-006: Failure Strain, min, 1.0% Test Temp @ 1.0 mm/min, C 0 -10 -20 -30 0 -10 -20 -30 0 -10 -20

Climatic Basisfor Spec

Binder Grades

Unaged (tank)binder

Aged (construction)binder

Aged (pavement)binder

Tests/Criteria Test Temp

1998- 2000What are the new challenges ?

We are not sure ..What temperatures to use in mixing and Compaction! Why modified binders are better for rutting!Not sure what is fatigue and how binders affect it! If Modifiers affect moisture damageIf MP1a (DTT – strength) makes a Difference!What to do about the RTFO and PAV for modified binders!

New / advanced testing needed for modified bitumens

ThermalCracking

FatigueCracking

PermanentDeformation

(mixing & compaction)

Pavement Temperature, C- 20 20 60 135

RTFOPAV

1. Viscosity at variable shear rate

4. Fracturestrengthstrain at failureglass transition

3. Binder fatigue

2. Binder repeated creep

5. SAFT 6. Cohesion

New Testing for Modified Bitumens

• Screening Testing: – LAST: Storage stability with/ without agitation– PAT : Particulate Additives

• Mixing and compaction temperatures• Performance Related

– Replace G*/sinδ with a binder rutting test – Replace G*sinδ with a binder fatigue test–Thermal Cracking

• Tg testing • Strain and stress at failure

165.0

Electric Motor2000 RPM

Temperature Controller(Brookfield)

Baffle (4)

TemperatureProbe

Internal Heater

Propeller(4 Blades)

Purge (N2)Sampling

Insulation

External Heater

Storage Stability The Lab Asphalt (bitumen) Stability Test (LAST)

Time,Temperature, & Agitation

Particulate Additive Test (PAT)

Mixing and Compaction Temperatures

1.E+03

1.E+05

2.E+05

3.E+05

4.E+05

5.E+05

6.E+05

1 10 100Shear Rate, 1/s

Visc

osity

, cps

Viscosityas a function of shear rate

ZSV

Unmodified Modified -2

Modified - 1

Old vs. NewCompaction Temperatures

100

120

140

160

180

200

0 5 10 15 20 25 30 35 40

Tem

p. C

Compaction T: 280 cP @ 6.81/s

Compaction T: 3000 cP @ ZSV

20-25 C Lower

Rutting: Do We Need to Change

G*/Sin d, and How?

For Modified BindersYES we do !

Current Test: Cyclic LoadingCould be OK only if elasticity is low

-40000

-30000

-20000

-10000

0

10000

20000

30000

40000

-20000 -10000 0 10000 20000

Torque (stress)

Strain 2%Strain 25%Strain 50%

Stress/Stress/StrainStrain

γγ22

ττ22

Can only give total energy: Total Wdissipated= π .τi

2 .sin δ/ G*= Welastic+ Wdelayed elastic+ Wviscous

This could be OK for conventional bitumens because they are mostly viscous. But not for modified elastic bitumens

Why is loading mode so important ?

Truck Load

Pavement Strain

Time

Time

b)

Time

Time

Viscous (Permanent)

Elastic + Delayed Elastic (Recoverable)

a)

Cannot Separate Permanent from Recovered !!!

Can

Current DSR Traffic – Repeated creep

Binder Rutting Test (DSR)

0.00

0.05

0.10

0.15

0.20

0 10 20 30

Time (seconds)

Stra

in (m

m/m

m)

Test data

Fit

Acc

um

ul a

ted

Str a

in

Cycles

To Separate non-recoverable Four-Element (Burgers) Model

G0, γ1

η1, γ2

η0, γ3

τ0

τ0

G1, γ2

Strain

Time

γ1

γ1

γ2

γ3

Elastic Response

Delayed -Elastic Response

Viscous Response

Simplest Analysis Method to Separate Permanent Strain

teGG

tJtJJtJ

tG

vdee

0

/

10

1)1(11)()()(

11

ηη +−+=

++=

−

where

Je = elastic compliance,

Jde = delayed elastic compliance, and

Jv = viscous compliance.

SS

Steady State Viscosity

Modification Can Reduce Damage

Creep Tests at 70C, 300 Pa shear stress (Loading 1s Recovery 9s) 100 cycles

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 200 400 600 800 1000

Time (s)

Acc

umul

ated

Str

ain

PG82- PEs

PG 82- Oxidized

PG-82- SBSr

Elastomer

Plastomer

No Additive

Stra

in ,

mm

/ mm

Time, sec

Multiple Stress Creep Recovery Test of Asphalt Binder Using a Dynamic Shear Rheometer (MSCR) –

AASHTO TP67

• Note: taken from D’Angelo 2005 [3]

Modified binders can improve resistance to RUTTING

FatigueDo we need to change G*.Sinδ ?

Yes For all Binders

Max Tensile Strain

Pavement Foundation

High ModulusRut Resistant Material(Varies As Needed)

Flexible Fatigue ResistantMaterial 3 - 4”

1.5 - 3” SMA, OGFC or Superpave4”to6”

ZoneOf High

Compression

Perpetual Pavements

0.0E+00

2.0E+06

4.0E+06

6.0E+06

8.0E+06

1.0E+07

1.2E+07

1.4E+07

1.6E+07

100 1000 10000 100000 1000000

Cycles

G* (

Pa)

Binders Vary Significantly In Fatigue Behavior

G*, Pa

Number of Cycles in the DSR

20000

400000What is measured initially is not maintained with time/cycles

Determination of Fatigue Life of Binders— Using the DSR

StrainStrain

StressStress ττmaxmax

γγmaxmax

Dissipated Energy Ratio• Pronk (DWW) defined the Ratio of dissipated

energy (Rde) as follows:

In whichWn = the total sum of the dissipated energy up

to cycle n, and∆Wn = the dissipate energy at cycle n.

n

nde

WW

R∆

=

Bitumen Damage BehaviorAs Related to Fatigue

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 2000 4000 6000 8000No. of Cycles

Dis

sipa

ted

Ener

gy R

atio

Np

Work on Binder Fatigue • Edge effects or fatigue

– 5-15 MPa range– Anderson et al. – Nynas (Soenen & Redelius )

• Compare standard Parallel Plate to other geometry/method.– Asphalt mastic (Little,Lytton, et al.)

• Mini mixture • High stiffness

• Rilem TG1– Round Robin study

Thermal Cracking

Visco-elasticityFailure StressFailure Strain Glass Transition

What Causes Thermal Cracking?

• Due to cooling, asphalt is subjected to stress.

dd

dE tt

∫ ′−=0

)()()( τττεξξσ

From BBR

Volume Change With Temperature From Tg

Cracking occurs if stress exceeds strength, or if strain exceeds strain tolerance

How Does Volume Change ?Glass Transition Measurements

Precision Capillary Tube

Silicon Rubber O-ringStainless Steal FittingPolypropylene

Washer

Housing

Base Cup Binder SpecimenSilicon Paper

-50,000

-40,000

-30,000

-20,000

-10,000

0

-80 -60 -40 -20 0 20 40

Temperature (C)

Spec

ific

Volu

me

Cha

nge

(1e-

6ml/g

)

Cell 0

Cell 1

AverageFit

Sample Tv0 (C) =40v=cv+ag(T-Tg)+R(al-ag)ln{1+exp[(T-Tg)/R]}

cv = Tg(C) = R = ag(10-6/C) = al(10

-6/C) = R2=

-27866 -24.85 5.542 196.5 429.7 0.9998

1αg

1

αl

Tg

Difference in Glass Transition

-60,000

-50,000

-40,000

-30,000

-20,000

-10,000

0

-80 -60 -40 -20 0 20 40Temperature (C)

Spec

ific

Volu

me

Cha

nge

(1e-

6ml/g

)

-24.6 -43.8

Load

Load

Measurementsection

11 mm

18 mm

11 mm

Reflective Tape

Typical Direct Tension Data As a function of Temperature

0.0

1.0

2.0

3.0

4.0

5.0

6.0

-25 -20 -15 -10 -5 0Temperature (C)

σfT

0/T (M

Pa)

0.0

3.0

6.0

9.0

12.0

15.0

18.0

εf

(%)

-6 C-12 C-18 C-24 CStress Fit-6 C-12 C-18 C-24 CStrain Fit

Temperature

Failure Strain“Ductility”

Strength

Future Trends

• Thermal Cracking– Tensile restrained test, Ring test

• S. Kim– Fracture test in bending

• Hesp and Marasteanu

• Aging– German Flask Test (DIN)– SAFT

• Anderson and Glover

• Adhesion / Cohesion– Thin Film Tackiness

• Konitpong and Bahia

Aging Procedures For Modified Bitumen

SAFT

X

Yes

Cohesion or Cohesion or Thin Film Tack (TFT) Testing with DSR

0.01 mm/s

Asphalt

SolidSurface

-50

-40

-30

-20

-10

0

10

20

55 60 65 70 75 80 85

Time (s)

Forc

e (N

)

Effect of Polymer Additives on Tackiness

Binder C T [s*N]

PG58-28(original): 56

PG58-28(0.5%Morlife): 48

PG64-28(SB): 110

PG64-28(SBS): 126

PG64-28(Elvaloy): 142

Asphalt Research Post SHRP --> Damage Resistance

Hard

Soft

Elastic

Viscous

Strong

WeakPen-Vis

SHRP Post SHRP

Concluding Remarks •Modification can improve Performance of Pavements significantly.

•Selection of modifiers –should be measured using damage behavior.– Linear visco-elastic testing (current Superpave) is not sufficient.

•Some modified asphalts require special handling and construction procedures.

Thank You for this

Opportunity

Questions !