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SUPERPAVE. FHWA Condensed Superpave Asphalt Specifications Lecture Series. Aggregates. Usually refers to a soil that has in some way been processed or sorted. 100 100 90 72 65 48 36 22 15 9 4. 100 99 89 72 65 48 36 22 15 9 4. Aggregate Size Definitions.

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superpave
SUPERPAVE

FHWA Condensed Superpave

Asphalt Specifications

Lecture Series

aggregates
Aggregates

Usually refers to a soil that has in some way been processed or sorted.

aggregate size definitions
100

100

90

72

65

48

36

22

15

9

4

100

99

89

72

65

48

36

22

15

9

4

Aggregate Size Definitions
  • Nominal Maximum Aggregate Size
    • one size larger than the first sieve to retain more than 10%
  • Maximum Aggregate Size
    • one size larger than nominal maximum size
slide4
Percent Passing

100

max density line

restricted zone

control point

nom

max

size

max

size

0

.075 .3 2.36 4.75 9.5 12.5 19.0

Sieve Size (mm) Raised to 0.45 Power

superpave aggregate gradation
Superpave Aggregate Gradation

Percent Passing

100

Design Aggregate Structure

0

.075 .3 2.36 12.5 19.0

Sieve Size (mm) Raised to 0.45 Power

superpave mix size designations
Superpave Mix Size Designations

Superpave Nom Max SizeMax Size

Designation (mm) (mm)

37.5 mm 37.5 50

25 mm 25 37.5

19 mm 19 25

12.5 mm 12.5 19

9.5 mm 9.5 12.5

slide7
-

Larger max size

Gradations

* Considerations:

- Max. size < 1/2 AC lift thickness

+ Increases strength

+ Improves skid resistance

+ Increases volume and surface area of agg which decreases required AC content

+ Improves rut resistance

+ Increases problem with segregation of particles

- Smaller max size

+ Reduces segregation

+ Reduces road noise

+ Decreases tire wear

percent crushed fragments in gravels
Percent Crushed Fragments in Gravels
  • Quarried materials always 100% crushed
  • Minimum values depended upon traffic level and layer (lift)
  • Defined as % mass with one or more fractured faces
percent crushed fragments in gravels9
Percent Crushed Fragments in Gravels

0% Crushed 100% with 2 or More

Crushed Faces

coarse aggregate angularity criteria
Traffic Depth from Surface

Millions of ESALs < 100 mm > 100 mm

< 0.3

< 1

< 3

< 10

< 30

< 100

 100

--/--

--/--

50/--

60/--

80/75

95/90

100/100

55/--

65/--

75/--

85/80

95/90

100/100

100/100

Coarse Aggregate Angularity Criteria

First number denotes % with one or more fractured faces

Second number denotes % with two or more fractured faces

asphalt cements

Asphalt Cements

Background

History of Specifications

background
Asphalt

Soluble in petroleum products

Generally a by-product of petroleum distillation process

Can be naturally occurring

Tar

Resistant to petroleum products

Generally by-product of coke (from coal) production

Background
penetration testing
Penetration in 0.1 mm

100 g

After 5 seconds

Initial

Penetration Testing
  • Sewing machine needle
  • Specified load, time, temperature
penetration specification
Penetration Specification
  • Five Grades
    • 40 - 50
    • 60 - 70
    • 85 - 100
    • 120 - 150
    • 200 - 300
typical penetration specifications
Typical Penetration Specifications

Penetration 40 - 50 200 - 300

Flash Point, C 450+ 350+

Ductility, cm 100+ 100+

Solubility, % 99.0+ 99.0+

Retained Pen., % 55+ 37+

Ductility, cm NA 100+

types of viscosity tubes
Types of Viscosity Tubes

Zietfuchs Cross-Arm Tube

Asphalt Institute Tube

table 1 example
Table 1 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+

slide20
Penetration Grades

AC 40

40

50

AC 20

60

70

AC 10

85

100

AC 5

120

150

AC 2.5

200

300

100

50

Viscosity, 60C (140F)

10

5

asphalt cements21
Asphalt Cements

New Superpave Performance Graded Specification

pg specifications
PG Specifications
  • Fundamental properties related to pavement performance
  • Environmental factors
  • In-service & construction temperatures
  • Short and long term aging
high temperature behavior
High Temperature Behavior
  • High in-service temperature
    • Desert climates
    • Summer temperatures
  • Sustained loads
    • Slow moving trucks
    • Intersections

Viscous Liquid

pavement behavior warm temperatures
Pavement Behavior(Warm Temperatures)
  • Permanent deformation (rutting)
  • Mixture is plastic
  • Depends on asphalt source, additives, and aggregate properties
permanent deformation
Permanent Deformation

Courtesy of FHWA

Function of warm weather and traffic

low temperature behavior
Low Temperature Behavior
  • Low Temperature
    • Cold climates
    • Winter
  • Rapid Loads
    • Fast moving trucks

Elastic Solid

Hooke’s Law

s = t E

pavement behavior low temperatures
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
thermal cracking
Thermal Cracking

Courtesy of FHWA

slide29
Superpave Asphalt Binder Specification

The grading system is based on Climate

PG 64 - 22

Min pavement temperature

Performance Grade

Average 7-day max pavement temperature

slide30
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)

slide31
Mi

t Rq=

2 p Ri2 L

W R

g =

Ro - Ri

Concentric Cylinder Rheometers

  • Concentric Cylinder
dynamic shear rheometer dsr
2 M

p R3

R Q

h

tR =

gR =

Dynamic Shear Rheometer (DSR)

Shear flow varies with gap height and radius

Non-homogeneous flow

  • Parallel Plate
slide33
Short Term Binder Aging
  • Rolling Thin Film Oven
    • Simulates aging from hot mixing and construction
slide34
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
bending beam rheometer
Bending Beam Rheometer

Computer

Deflection Transducer

Air Bearing

Load Cell

Fluid Bath

direct tension test
Direct Tension Test

Load

Stress = s = P / A

D L

sf

D Le

ef

Strain

summary
PAV

Long Term Aging

RTFO

Short Term Aging

No aging

Summary

Low Temp

Cracking

Fatigue

Cracking

Rutting

Construction

[DTT]

[RV]

[DSR]

[BBR]

slide39
Superpave Asphalt Binder Specification

The grading system is based on Climate

PG 64 - 22

Min pavement temperature

Performance Grade

Average 7-day max pavement temperature

slide40
Performance Grades

CEC

Avg 7-day Max, oC

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

1-day Min, oC

-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

ORIGINAL

> 230 oC

(Flash Point) FP

<[email protected] oC

(Rotational Viscosity) RV

(Dynamic Shear Rheometer) DSR G*/sin 

> 1.00 kPa

46 52 58 64 70 76 82

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

(Dynamic Shear Rheometer) DSR G*/sin 

> 2.20 kPa

46 52 58 64 70 76 82

(PRESSURE AGING VESSEL) PAV

20 Hours, 2.07 MPa

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

(Dynamic Shear Rheometer) DSR G* sin 

< 5000 kPa

28

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

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

S < 300 MPa

m > 0.300

-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

Report Value

(Bending Beam Rheometer) BBR Physical Hardening

> 1.00 %

(Direct Tension) DT

-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

slide41
How the PG Spec Works

58

64

CEC

Spec Requirement

Remains Constant

Avg 7-day Max, oC

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

1-day Min, oC

-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

ORIGINAL

> 230 oC

(Flash Point) FP

<[email protected] oC

(Rotational Viscosity) RV

(Dynamic Shear Rheometer) DSR G*/sin 

> 1.00 kPa

46 52 58 64 70 76 82

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

(Dynamic Shear Rheometer) DSR G*/sin 

> 2.20 kPa

46 52 58 64 70 76 82

(PRESSURE AGING VESSEL) PAV

20 Hours, 2.07 MPa

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

Test Temperature

Changes

(Dynamic Shear Rheometer) DSR G* sin 

< 5000 kPa

28

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

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

S < 300 MPa

m > 0.300

-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

Report Value

(Bending Beam Rheometer) BBR Physical Hardening

> 1.00 %

(Direct Tension) DT

-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

slide42
PG Binder Selection

> Many agencies have

established zones

PG 52-28

PG 58-22

PG 58-16

PG 64-10

summary of how to use pg specification
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
hot mix asphalt concrete hma mix designs
Hot Mix Asphalt Concrete (HMA)Mix Designs
  • Objective:
    • Develop an economical blend of aggregates and asphalt that meet design requirements
  • Historical mix design methods
    • Marshall
    • Hveem
  • New
    • Superpave gyratory
requirements in common
Requirements in Common
  • Sufficient asphalt to ensure a durable pavement
  • Sufficient stability under traffic loads
  • Sufficient air voids
    • Upper limit to prevent excessive environmental damage
    • Lower limit to allow room for initial densification due to traffic
  • Sufficient workability
marshall mix design
Marshall Mix Design
  • Developed by Bruce Marshall for the Mississippi Highway Department in the late 30’s
  • WES began to study it in 1943 for WWII
    • Evaluated compaction effort
      • No. of blows, foot design, etc.
      • Decided on 10 lb.. Hammer, 50 blows/side
      • 4% voids after traffic
  • Initial criteria were established and upgraded for increased tire pressures and loads
marshall mix design49
Marshall Mix Design
  • Select and test aggregate
  • Select and test asphalt cement
    • Establish mixing and compaction temperatures
  • Develop trial blends
    • Heat and mix asphalt cement and aggregates
    • Compact specimen (100 mm diameter)
marshall design criteria
Marshall Design Criteria

Light Traffic Medium Traffic Heavy Traffic

ESAL < 104 10 4 < ESAL< 10ESAL > 106

Compaction 35 50 75

Stability N (lb.) 3336 (750) 5338 (1200) 8006 (1800)

Flow, 0.25 mm (0.1 in) 8 to 18 8 to 16 8 to 14

Air Voids, % 3 to 5 3 to 5 3 to 5

Voids in Mineral Agg.

(VMA) Varies with aggregate size

superpave volumetric mix design
Superpave Volumetric Mix Design
  • Goals
    • Compaction method which simulates field
    • Accommodates large size aggregates
    • Measure of compactibility
    • Able to use in field labs
    • Address durability issues
      • Film thickness
      • Environmental
slide53
Compaction

Key Components of Gyratory Compactor

height

measurement

control and data

acquisition panel

reaction

frame

loading

ram

mold

tilt bar

rotating

base

compaction
Compaction
  • Gyratory compactor
    • Axial and shearing action
    • 150 mm diameter molds
      • Aggregate size up to 37.5 mm
      • Height measurement during compaction
        • Allows densification during compaction to be evaluated

Ram pressure

600 kPa

1.25o

slide55
Three Points on SGC Curve

% Gmm

Nmax

Ndes

Nini

10 100 1000

Log Gyrations

sgc critical point comparison
SGC Critical Point Comparison

%Gmm= Gmb / Gmm

Gmb = Bulk Mix Specific Gravity from compaction at N cycles

Gmm = Max. Theoretical Specific Gravity

Compare to allowable values at:

NINI : %Gmm < 89%

NDES: %Gmm < 96%

NMAX: %Gmm < 98%

design compaction
Design Compaction
  • Ndes based on
    • average design high air temp
    • traffic level
  • Log Nmax = 1.10 Log Ndes
  • Log Nini = 0.45 Log Ndes

% Gmm

Nmax

Ndes

Nini

10 100 1000

Log Gyrations

slide58
Superpave Testing
  • Specimen heights
  • Mixture volumetrics
    • Air voids
    • Voids in mineral aggregate (VMA)
    • Voids filled with asphalt (VFA)
    • Mixture density characteristics
  • Dust proportion
  • Moisture sensitivity
superpave mix design
Superpave Mix Design
  • Determine mix properties at NDesign and compare to criteria
    • Air voids 4% (or 96% Gmm)
    • VMA See table
    • VFA See table
    • %Gmm at Nini < 89%
    • %Gmmat Nmax < 98%
    • Dust proportion 0.6 to 1.2
superpave mix design60
Superpave Mix Design

Gyratory Compaction Criteria