1

Properties of Asphalt Binder

General Asphalt Binder Properties

• Adheres well to most rock

• Waterproof

• Fairly durable

• Resistant to reaction with most acids,

alkalis, and salts

• Temperature sensitive

2

Binder Performance is affected by:

• Temperature

• Rate of Loading

• Aging

60 C

25 C

1 hour

1 hour

Time vs. Temperature

10 hours

Time-Temperature Superposition

3

Temperature Susceptibility

Temperature, °C

Stiffness (Response to Load)

-30 25 60 135

elastic

viscous

elasticsolid

viscousfluid

At High

Tmp. Or

Slow

TrucksAt Low

Tmp. Or

fast Trucks

Temperature Susceptibility

Log Temperature

Too brittle (Thermal cracking)

Too soft (Rutting)

Optimum range

Of viscosity

Log L

og (

Vis

cosi

ty)

4

Temperature Susceptibility

Log Temperature

Soft

Log

Lo

g (

Vis

cosi

ty)

Hard

Soft asphalt is used in cold climatesHard asphalt is used in hot climates

Effect of Rate of Loading

5

Material Models

(Yoder and Witczak, 1974)

Aging Behavior

• CausesOxidation

Volatilization

Physical hardening

• TypesShort-term aging

Long-term aging

6

Modified Asphalt

Asphalt properties can be improved with

polymer and other modifiers

Temperature susceptibility

Adhesion to aggregates (Reduce Stripping)

Resistance to permanent deformation

Resistance to fatigue cracking

Elasticity, ductility, and durability

Traditional Tests:1 Penetration test

2 Ring and Ball Softening Point test

3 Absolute Viscosity test

4 Kinematic Viscosity test

Flash Point test

Performance Grade (Superpave) tests:1 Rotational Viscometer (Brookfield) test

2 Dynamic Shear Rheometer (DSR) test

3 Bending Beam Rheometer (BBR) test

4 Direct Tension (DT) test

5 Rolling Thin Film Oven (RTFO) test

6 Pressure Aging Vessel (PAV) test

7 Flash Point test

Characterization of Asphalt Binder

7

Classification of Asphalt Cement

• Based on penetration

• Based on viscosity

• Based on viscosity after aging

• Based on performance (Superpave)

Penetration Specifications

8

Penetration Test

100g100g

penetration

0 sec 5 sec

Penetration Specification

Five Grades

• 40 - 50

• 60 - 70

• 85 - 100

• 120 - 150

• 200 - 300Maximum penetration

Minimum penetration

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Penetration Gradation Specification

• Uses penetration results to specify

• Adds

– Flash point test

– Ductility

– Solubility

– Thin film oven aging

• Penetration

• Ductility

Flash Point (Safety)

Thermometer

Cup filled with

asphalt binder

Wand attached

to gas line

10

Ductility

Solubility (Purity)

11

Thin Film Oven

Outside of Oven Rotating Shelf

Pan Thermometer

163 oC oven for 5 hours.

Classical Penetration- Based Specification

Min Max Min Max Min Max Min Max Min Max

Penetration @ 77°F(25°C) 100g, 5s 40 50 60 70 85 100 120 150 200 300

Flash Point, °F (Cleveland open cup) 450 --- 450 --- 450 --- 425 --- 350 ---

Ductility at 77°F (25°C) 5cm/min, cm 100 --- 100 --- 100 --- 100 --- 100A ---

Solubility in trichloroethylene, % 99 --- 99 --- 99 --- 99 --- 99 ---

Retained penetration after thin-film 55+ --- 52+ --- 47+ --- 42+ --- 37+ ---

oven test, %

Ductility at 77°F (25°C) 5cm/min, cm --- --- 50 --- 75 --- 100 --- 100A ---

after thin-film oven test

40-50 60-70 85-100 120-150 200-300

Penetration Grade

A If ductility at 77°F (25°C) is less than 100 cm, material will be accepted if ductility at 60°F (15.5°C) is 100 cm minimum

at the pull rate of 5 cm/min

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Temperature

25C (77F)

High

Medium

Low

Advantages of Penetration

Specifications

• Grades asphalt binders near average in-service

temp.

• Fast

• Can be used in field labs

• Low cost of Equipment

• Precision well established

• Temp. susceptibility can be determined

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Disadvantages

• Empirical test

• Shear rate

– High

– Variable

• Mixing and compaction temperature information not

available

• Similar penetrations at 25C (77F) do not reflect wide

differences in asphalts

Viscosity Graded Specifications

14

Viscosity: is defined as the resistance of the

material to flow.

Viscosity: is the ratio between the applied

shear stress and the rate of shear strain.

h = t / g

Definition

Units of Viscosity

• Pa.S = Pascal. Second

• cS = Centi Stoke

• cP = Centi Poise

• P = PoisePa.S = 1000 cP

P = 100 cP

Stoke = 100 cS

cS = cP / Gb

15

Viscosity Tests vacuum

CANNON

CANNON

100100

A9A9

Timing Marks

Viscometers

Absolute Viscosity Test

• Absolute viscosity

– U-shaped tube with

timing marks & filled

with asphalt binder

– Placed in 60C bath

– Vacuum used to pull

asphalt through tube

– Time to pass marks

– Visc. in Pa s (Poise)

16

Kinematic Viscosity Test

• Kinematic viscosity– Cross arm tube with timing

marks & filled with asphalt

– Placed in 135C bath

– Once started gravity moves

asphalt through tube

– Time to pass marks

– Visc. in mm2 / s (centistoke)

Viscosity Grade Specifications

• Viscosities at 60 and 135oC

• Penetrations at 25oC

• Flash point

• Solubility

• TFO aged residue

– Viscosity at 60oC

– Ductility at 25oC

17

AC Grades (Viscosity Grades)

AC-2.5, AC-5, AC-10

AC-20, AC-30, AC-40

AC- # 1/100 of midpoint of the allowable viscosity range.

AC-20, viscosity range 1,600 to 2,400 poises.

Asphalt cement

AC Grades Example

AC 2.5 AC 40

Visc, 60C 250 + 50 4,000 + 800

Visc, 135C 80+ 300+

Penetration 200+ 20+

Visc, 60C <1,250 <20,000

Ductility 100+ 10+

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Log Temperature

25C (77F) 60C (140F) 135C (275F)

Ave.

Service

Temp.

Mixing

&

Compaction

Hot

SummerL

og

Lo

g V

isc

os

ity (

Sti

ffn

es

s)

Advantages of (Original AC Visc. Grade)

• Fundamental property

• Wide range of temperatures

• Based on max. pavement surface temp.

• Wide range of instruments

• Test method precision established

• Temperature susceptibility is controlled

• Limits aging

• Information on mixing & compaction temps.

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Disadvantages

(Original AC Visc. Grade)

• More expensive

• Longer testing time

• More technician skill needed

• Not applicable for Non-Newtonian materials

• Wide range of properties for same grade

Viscosity After Aging Graded

Specifications

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AR Grades

AR-10, AR-20, AR-40

AR-80, AR-160

AR- # 1/100 of midpoint of viscosity after aging.

AR-40, viscosity range 3,000 to 5,000 poises.

Aged Residue

AR Grades Specifications

• AR Grades

– AR 1000, AR 2000, AR 4000,

AR 8000, AR 16000

• Tests on RTFO aged residue

– Viscosities at 60 and 135oC

– Penetrations at 25oC

– % of Original Penetration

– Ductility

– Properties of unaged asphalt

binders

• Flash point and solubility

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Fan

Air Line

Rotating

Bottle

Carriage

BeforeAfter

Rolling Thin Film Oven Test (RTFOT)

163oC in Oven, for

80 minutes

Advantages

(AR Visc. Grade)

• Represents asphalt binder properties after

mixing

• Fundamental properties

• Covers wide range of temperatures

• Limits aging

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Disadvantages

(AR Visc. Grade)

• Highly regional

• Requires different testing equipment

• Longer testing time

• No consistency test on original Asphalt Binder

• Not applicable for Non-Newtonian materials

• Wide range of properties for same grade

40

50

60

7085

100

120

150200

300

Penetration Grades

AC 40

AC 20

AC 10

AC 5

AC 2.5

100

50

10

5

Vis

co

sit

y, 6

0C

(14

0F

) AR 16000

AR 8000

AR 4000

AR 2000

AR 1000

Comparison of the Various Traditional

Specifications

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Mixing and Compaction Temperatures

– MS-2

• Recommended laboratory mixing and compaction

temperature ranges for Marshall mix design based on

viscosity (Saybolt Furol) as early as 1962.

– Changed to absolute and kinematic viscosity in 1974.

– 170 ± 20 centipoise for mixing

– 280 ± 30 centipoise for compaction

– Purpose

• Normalize the effect of asphalt binder stiffness on

mixture volumetric properties

– Aggregate packing and available void space

Log Temperature, R

Log L

og V

isco

sity

, cP

Compaction Range

Mixing Range

Mixing/Compaction Temps

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Ai-VTSi

Temperature - Viscosity Relationship for:

PG 64-22, Tank Condition

y = -3.8785x + 11.519

R2 = 0.992

0.0

0.2

0.4

0.6

0.8

1.0

1.2

2.70 2.75 2.80 2.85 2.90 2.95

Log (Temp) (R)

Log L

og (

Vis

c)

(cP

)

Background

• Modified Asphalt Binders in the Superpave Mix

Design System

• Adopted old (Marshall) standard in 1993– 170 ± 20 centipoise for mixing

– 280 ± 30 centipoise for compaction

• Manufacturer’s recommendation for

modified asphalt binders:

- based on PG grade

- based on field experience