New Binder Specification SUPERPAVE...Superpave Asphalt BinderSpecification The grading system is...

1

Asphalt Cements

- New Superpave

Performance Graded

Specification

2

PG Specifications

• Fundamental properties related to

pavement performance

• Environmental factors

• In-service & construction temperatures

• Short and long term aging

3

PG Specifications

• Based on rheological testing

– Rheology: study of flow and deformation

• Asphalt cement is a viscoelastic material

• Behavior depends on:

– Temperature

– Time of loading

– Aging (properties change with time)

4

High Temperature Behavior

• High in-service temperature

– Desert climates

– Summer temperatures

• Sustained loads

– Slow moving trucks

– Intersections

Viscous Liquid

5

Pavement Behavior

(Warm Temperatures)

• Permanent deformation (rutting)

• Mixture is plastic

• Depends on asphalt source, additives,

and aggregate properties

6

Permanent Deformation

Function of warm weather and traffic

Courtesy of FHWA

7

Low Temperature Behavior

• Low Temperature

– Cold climates

– Winter

• Rapid Loads

– Fast moving trucks

Elastic Solid

s = t E

Hooke’s Law

8

Pavement Behavior

(Low Temperatures)

• Thermal cracks

– Stress generated by contraction due to

drop in temperature

– Crack forms when thermal stresses

exceed ability of material to relieve

stress through deformation

• Material is brittle

• Depends on source of asphalt and

aggregate properties

9

Thermal Cracking

Courtesy of FHWA

10

Aging

• Asphalt reacts with oxygen

– “oxidative” or “age hardening”

• Short term

– Volatilization of specific components

– During construction process

• Long term

– Over life of pavement (in-service)

11

Superpave Asphalt Binder Specification

The grading system is based on Climate

PG 64 - 22

Performance

Grade

Average 7-day max

pavement temperature

Min pavement

temperature

12

Pavement Temperatures are Calculated

• Calculated by Superpave software

• High temperature

– 20 mm below the surface of mixture

• Low temperature

– at surface of mixture

Pave temp = f (air temp, depth, latitude)

13

RV DSR BBR

Construction

Tests Used in PG Specifications

14

Concentric Cylinder

Concentric Cylinder Rheometers

t Rq = Mi

2 p Ri2 L

g =

W R

Ro - Ri

15

Rotational Viscometer

(Brookfield)

Inner Cylinder

Torque Motor

Thermosel

Environmental

Chamber

Digital Temperature

Controller

16

RV

DSR

BBR

Original Properties, Rutting, and Fatigue

17

Dynamic Shear Rheometer (DSR)

• Parallel Plate Shear flow varies with

gap height and radius

Non-homogeneous flow

gR =

R Q

h

tR =

2 M

p R3

18 1 cycle

Time A

A

B

C

C

A

B

Fixed Plate

Oscillating Plate

Test operates at 10 rad/sec

or 1.59 Hz

360o = 2 p radians per circle

1 rad = 57.3o

19

Elastic Viscous

Time A

A

B

C

Strain

Strain in-phase

d = 0o

Strain out-of-phase

d = 90o

20

Viscous Modulus, G”

Storage Modulus, G’

Complex Modulus, G*

d

Complex Modulus is the vector sum of the

storage and viscous modulus

21

DSR Equipment DSR

Equipment Computer Control

and Data

Acquisition

22

Area for

Liquid Bath

Motor

Parallel Plates

with Sample

23

25 mm Plate with Sample

24

RV

DSR

BBR

Rutting

25


Addressed by:

G*/sin d on unaged binder > 1.00 kPa

G*/sin d on RTFO aged binder > 2.20 kPa

For the early part

of the service life

26

Short Term Binder Aging

• Rolling Thin Film Oven

– Simulates aging from hot mixing and construction

27

Inside of RTFO

Fan

Air Line

Rotating

Bottle

Carriage

28

Bottles Before and After Testing

Opening in

Bottle

29

Testing

• Calculate mass loss after RTFO

• Determine G*/sin d for RTFO aged material at

same test temp. used for original asphalt

cement

Mass loss, % =

Original mass - Aged mass

Original mass

x 100

30

Question: Why a minimum G*/sin d to

address rutting

Answer: We want a stiff, elastic binder to

contribute to mix rutting resistance

How: By increasing G* or decreasing d


31

RV

DSR

BBR

Fatigue

32

Fatigue Cracking

Function of repeated traffic loads over time

(in wheel paths)

33

Testing

• Aged binder

– Since long term performance problem,

include:

• Short term aging

• Long term aging

• Determine DSR parameters using 8 mm

plate and intermediate test temperature

34

Pressure Aging Vessel

(Long Term Aging)

• Simulates aging of an asphalt binder

for 7 to 10 years

• 50 gram sample is aged for 20 hours

• Pressure of 2,070 kPa (300 psi)

• At 90, 100 or 110 C

35

Bottom of

pressure aging

vessel

Rack of individual pans

(50g of asphalt / pan)


Vessel Lid Components

36


Courtesy of FHWA

37

Fatigue Cracking

• G* (sin d) on RTFO and PAV aged binder

• The parameter addresses the later part of

the fatigue life

• Value must be < 5000 kPa

38

Fatigue Cracking

• Question: Why a maximum G* sin d to

address fatigue?

Answer: We want a soft elastic binder (to

sustain many loads without cracking)

How: By decreasing G* or decreasing d

39

RV DSR

BBR

Thermal

Cracking

40

Bending Beam Rheometer

Air Bearing

Load Cell

Deflection Transducer

Fluid Bath

Computer

41

Bending Beam Rheometer Sample

42

Bending Beam Rheometer Equipment

Cooling

System

Fluid Bath Loading

Ram

43


• S(t) = P L3

4 b h3 d (t)

Where:

S(t) = creep stiffness (M Pa) at time, t

P = applied constant load, N

L = distance between beam supports (102 mm)

b = beam width, 12.5 mm

h = beam thickness, 6.25 mm

d(t) = deflection (mm) at time, t

44


• Evaluates low temperature stiffness

properties

– Creep stiffness

– Slope of response (called m-value)

8 15 30 60 120 240

Log Creep

Stiffness, S(t)

Log Loading Time, t (sec)

45

Is Stiffness Enough?

• No. Need to assess strain needed to

break specimen.

– Thermal cracking occurs when strain is

too great

• Direct tension test

– Currently (1998) in specification

• New equipment is now available

46

Direct Tension Test

D Le

D L

Load

Stress = s = P / A

Strain ef

sf

47

FHWA

Direct Tension Test

Courtesy of FHWA

48

Direct Tension Test

Courtesy of FHWA

49

Summary

Fatigue

Cracking Rutting

RTFO

Short Term Aging No aging

Construction

[RV] [DSR]

Low Temp

Cracking

[BBR]

[DTT]

PAV

Long Term Aging

Superpave Binder

Purchase

Specification

Superpave Asphalt Binder

Specification

The grading system is based on Climate

PG 64 - 22

Performance

Grade

Average 7-day max

pavement temperature

Min pavement

temperature

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

2

8

-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, oC

1-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

Performance Grades

(Dynamic Shear Rheometer) DSR G*/sin d


< 3 Pa.s @ 135 oC

> 230 oC

CEC

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


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


(Direct Tension) DT


2

8

-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, oC

1-day Min, oC


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



-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

How the PG Spec Works



< 3 Pa.s @ 135 oC

> 230 oC

CEC

58 64

Test Temperature

Changes

Spec Requirement

Remains Constant

> 1.00 kPa

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


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


(Direct Tension) DT


2

8

-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, oC

1-day Min, oC


ORIGINAL

< 5000 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



-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




< 3 Pa.s @ 135 oC

> 230 oC

CEC

> 1.00 kPa

> 2.20 kPa •Unaged

•RTFO Aged


• Addressed by high temp stiffness

– G*/sin d on unaged binder > 1.00 kPa

– G*/sin d on RTFO aged binder > 2.20 kPa

> Early part of

pavement

service life

Heavy Trucks

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


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


(Direct Tension) DT


2

8

-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, oC

1-day Min, oC


ORIGINAL

> 1.00 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



-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

Fatigue Cracking



< 3 Pa.s @ 135 oC

> 230 oC

CEC

< 5000 kPa

PAV Aged

Fatigue Cracking

• Addressed by intermediate

temperature stiffness

–G*sin d on RTFO & PAV

aged binder < 5000 kPa

> Later part of

pavement service life

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


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


(Direct Tension) DT


2

8

-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, oC

1-day Min, oC


ORIGINAL

> 1.00 kPa

< 5000 kPa

> 2.20 kPa

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



-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

Low Temperature Cracking



< 3 Pa.s @ 135 oC

> 230 oC

CEC

S < 300 MPa m > 0.300

Report Value

> 1.00 %

PAV Aged

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


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


(Direct Tension) DT


2

8

-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, oC

1-day Min, oC


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



-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

Miscellaneous Spec Requirements



CEC

< 3 Pa.s @ 135 oC

> 230 oC Flash

Point

Mass

Loss

PG 64 - 16

PG 58-22

PG 52-28

PG 64-10 PG 58-16

> Many agencies have

established zones

PG Binder Selection

Developed from Air Temperatures

• Superpave Weather Database

– 6500 stations in U.S. and Canada

• Annual air temperatures

– hottest seven-day temp (avg and std

dev)

– coldest temp (avg and std dev)

• Calculated pavement temps used in PG

selection

> 20 years

Reliability

• Percent Probability of Not Exceeding Design

Temp

frequency of

observed temps

(Total area under

curve = 100 %)

Tavg Tdes

Reliability is area under curve

to the left of Tdes

> using Normal Distribution

36 40

7-Day Maximum Air Temperatures

50 % reliability

98 % reliability

Observed Air Temperatures Topeka, KS

average summer

very hot summer

> this data - standard

deviation of 2°C

36

40

-23 -31

0 10 20 30 40 50 60 -10 -20 -30 -40

Observed Air Temperatures

Topeka, KS

average winter

> standard

deviation of 4°C

very cold winter

Convert to Pavement Temperature

• Calculated by Superpave

software

• High Temperature

– 20 mm below surface of

mixture

• Low Temperature

– at surface of mixture

Pavt Temp = f ( Air Temp, Depth, Latitude )

56

60

-23 -31

0 10 20 30 40 50 60 -10 -20 -30 -40 70

Calculated Pavement Temperatures Topeka, KS

pvt = air

pvt > air

0 10 20 30 40 50 60 -10 -20 -30 -40 70

PG 64-34 (98% minimum reliability)

PG 58-28 (50 % minimum reliability)

PG Binder Grades Topeka, KS

PG grades - six degree

increments

0 10 20 30 40 50 60 -10 -20 -30 -40 70

PG 58-28 (50 % minimum reliability)

Effect of Rounding to Standard Grades

PG 58 provides 85% reliability

PG -28 provides 90% reliability

Effect of Rounding to Standard

Grades

needed grade

for 50% reliability

-23 -28

Minimum Pavement Temperatures

selected grade

for 50% reliability Rounding depends

on actual temps!

-16 -22 -28

Effect of Loading Rate on

Binder Selection

• Dilemma

– specified DSR loading rate is 10 rad/sec

– what about longer loading times ?

• Use binder with more stiffness at higher

temps

– slow - - increase one high temp grade

– stationary - - increase two high temp grades

– no effect on low temp grade

90 kph

Effect of Loading Rate on

Binder Selection

• Example

– for toll road PG 64-22

– for toll booth PG 70-22

– for weigh stations PG 76-22

90 kph

Slow

Stopping

Effect of Traffic Amount

on Binder Selection

• 10 - 30 x 106 ESAL

– Consider increasing - - one high temp

grade

• 30 x 106 + ESAL

– Recommend increasing - - one high

temp grade

80 kN ESALs

> Equivalent Single Axle Loads

ESAL Comparison

80 kN

18,000 lb.

100 kN

22,000 lb.

44 kN

10,000 lb.

1

ESAL

2.2

ESAL

.09

ESAL

67 kN

15,000 lb

0.48 ESAL

27 kN

6,000 lb

0.01 ESAL + =

151 kN

34,000 lb

1.10

151 kN

34,000 lb

1.10 + =

54 kN

12,000 lb

0.19 +

0.49 ESALs

2.39 ESALs

BIG TRUCK

Little Truck

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


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


(Direct Tension) DT


2

8

-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, oC

1-day Min, oC


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



-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

How the PG Spec Works



< 3 Pa.s @ 135 oC

> 230 oC

CEC

58 64

Test Temperature

Changes

Spec Requirement

Remains Constant

> 1.00 kPa

Summary of How to Use

PG Specification

• Determine

–7-day max pavement temperatures

–1-day minimum pavement

temperature

• Use specification tables to select

test temperatures

• Determine asphalt cement

properties and compare to

specification limits

Questions - ?

82

Questions - ?

New Binder Specification SUPERPAVE...Superpave Asphalt BinderSpecification The grading system is...

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