block 4 sp 14

Asphalt Binders Superpave Binder Tests 1

Asphalt Binders

Superpave Performance Graded Specification

Senior/GraduateHMA Course

Asphalt Binders Superpave Binder Tests 2

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

Asphalt Binders Superpave Binder Tests 3

Pavement Temperatures are Calculated

• Calculated by Superpave software• High temperature

– 20 mm (.8”) below the surface of mixture

• Low temperature– at surface of mixture

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

www.tfhrc.gov/pavement/ltpp/ltppbind.htm

Asphalt Binders Superpave Binder Tests 4

PG Specification Tests

• Rheology– Fundamental properties related to HMA

performance• Test parameters

– Selected to represent in-service & construction temperatures

• Asphalt binder conditioning– Environmental factors

•Short and long term aging

Asphalt Binders Superpave Binder Tests 5

Rheological Tests Selected

• Concentric Cylinders• Dynamic shear rheometer• Bending beam• Direct tension

Asphalt Binders Superpave Binder Tests 6

RV DSR BBR

Construction

Tests Used in PG Specifications

Asphalt Binders Superpave Binder Tests 7

Construction Asphalt Binder Properties

• Concentric cylinder rheometer– Used to insure a minimum

workability (pumpability) at typical mixing temperature

– Maximum viscosity 3kPa at 135oC (275 F)

Construction

[RV]

Asphalt Binders Superpave Binder Tests 8

RV

DSR

BBR

Rutting

Asphalt Binders Superpave Binder Tests 9

Rutting• High in-service temperature

– Desert climates– Summer temperatures

• Sustained loads– Slow moving trucks– Intersections

Viscous Liquid

Asphalt Binders Superpave Binder Tests 10

Rutting

• DSR testing– Minimum stiffness requirement

•Original asphalt binder•Immediately after construction

–Short term aging Rutting

[DSR]

Asphalt Binders Superpave Binder Tests 11

High In-Service Temperatures

• Permanent deformation (rutting)• Mixture is plastic• Depends on asphalt binder source,

additives, and aggregate properties

Function of warm weather and traffic

Asphalt Binders Superpave Binder Tests 12

Asphalt Binders Superpave Binder Tests 13

Short Term Aging

• Simulates stiffening of asphalt binder during storage, mixing, and hauling

• Function of:– Oxidation hardening

•Asphalt binder reacts with oxygen•Volatilization of specific components

• Simulated using rolling thin film oven

Asphalt Binders Superpave Binder Tests 14

Short Term Aging• Rolling Thin Film Oven Test (RTFOT)

– Simulates aging from hot mixing and construction

Asphalt Binders Superpave Binder Tests 15

Mass Loss is Monitored

• Calculate mass loss after RTFO

Mass loss, % =Original mass - Aged mass

Original mass

x 100

Asphalt Binders Superpave Binder Tests 16

RuttingSuperpave DSR test requirements:

G*/sin on unaged (original) asphalt binder > 1.00 kPa

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

For the early part of the service life

Asphalt Binders Superpave Binder Tests 17

RV

DSR

BBR

Fatigue

Asphalt Binders Superpave Binder Tests 18

Fatigue Cracking

Function of repeated traffic loads over time(in wheel paths)

Asphalt Binders Superpave Binder Tests 19

DSR

• Aged PG asphalt binder– Since long term performance

problem, include:•Short term aging•Long term aging

• Determine DSR parameters using 8 mm plate and intermediate test temperature

FatigueCracking

[DSR]

Asphalt Binders Superpave Binder Tests 20

Long Term Aging

• Simulates aging of an PG asphalt binder for 7 to 10 years

• Starts with RTFO aged PG asphalt binder– Additional aging with Pressure Aging

Vessel (PAV)•50 gram (1.75 oz)

Asphalt Binders Superpave Binder Tests 21

PAV Components

Bottom of pressure

aging vessel

Rack of individual pans

(50g of asphalt / pan)

Vessel Lid Components

Asphalt Binders Superpave Binder Tests 22

PAV Testing

• After RTFO aging– 50 gram sample/pan aged for 20 hours

in PAV•Pressure of 2,070 kPa (300 psi)•Test temp 90, 100 or 110o C (194,

212,or 230 F)• The parameter addresses the later part of

the fatigue life

Asphalt Binders Superpave Binder Tests 23

Equipment Examples

Asphalt Binders Superpave Binder Tests 24

RV DSRBBR

Thermal Cracking

Asphalt Binders Superpave Binder Tests 25

Low Temperature Behavior

• Low Temperature– Cold climates– Winter

• Rapid Loads– Fast moving trucks

Elastic Solid

E

Hooke’s Law

Asphalt Binders Superpave Binder Tests 26

Low Temperature

• 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

Asphalt Binders Superpave Binder Tests 27

Thermal Cracking

Asphalt Binders Superpave Binder Tests 28

Low Temperature

• Two rheological tests– Bending beam

•Stiffness– Direct tension

•Strength

Low TempCracking

[BBR]

[DTT][DTT]

Asphalt Binders Superpave Binder Tests 29

Superpave Requirements

• BBR Stiffness Properties– Max stiffness, S, at 60 seconds of 300

MPa– Min rate of change in stiffness

•Min slope, m, of 0.300 MPa/sec• Strength

– Currently being finalized

Asphalt Binders Superpave Binder Tests 30

Summary

FatigueCrackingRutting

RTFOShort Term AgingNo aging

Construction

[RV] [DSR]

Low TempCracking

[BBR]

[DTT][DTT]

PAVLong Term Aging

Asphalt Binders Superpave Binder Tests 31

QUESTIONS ?