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2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP...

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Asphalt Mixture Characteristics Affecting Durability Cracking Mike Anderson 11 th Arizona Pavements/Materials Conference November 19-20, 2014 Tempe, AZ
Transcript
Page 1: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Asphalt Mixture Characteristics Affecting Durability Cracking

Mike Anderson

11th Arizona Pavements/Materials ConferenceNovember 19-20, 2014Tempe, AZ

Page 2: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Acknowledgments

• Kentucky Department of Highways• Allen Myers

• Kentucky Transportation Center/University of Kentucky

• Clark Graves, Dr. Kamyar Mahboub• Federal Highway Administration

• John D’Angelo• National Cooperative Highway Research

Program• NCHRP 9-25, 9-29, 9-33• Dr. Don Christensen, Dr. Ramon Bonaquist

• Member Companies of the Asphalt Institute

Page 3: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Durability

• NCHRP Report 673, “A Manual for Design of Hot Mix Asphalt with Commentary”

• Resistance of asphalt mixture to disintegration due to the combined effects of weathering and traffic

• Surface (wearing) mixes have most severe exposure• The most durable mixes have…

• Good fatigue resistance• Low permeability to air and water

Page 4: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Importance of Air Voids

• Field performance has shown that typical mixtures designed with low air voids (maybe < 2%) are susceptible to rutting and shoving

• Mixtures designed over about 5% air voids are susceptible to raveling, oxidation and a general lack of durability

• 4% air void design is an empirically derived target that allows for thermal expansion of the binder along with a cushion for future compaction

Page 5: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Importance of VMA

• VMA is the volume of the voids in a compacted aggregate sample to accommodate asphalt and air.

• Assure sufficient binder coating

• Maintain 4% Air voids

Page 6: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Durability

• NCHRP Report 673, “A Manual for Design of Hot Mix Asphalt with Commentary”

• Resistance of asphalt mixture to disintegration due to the combined effects of weathering and traffic

• Surface (wearing) mixes have most severe exposure• The most durable mixes have…

• Good fatigue resistance• Low permeability to air and water

• To accomplish this…• High binder content• Reasonable amount of fine material

• …and most importantly…• Well-compacted during construction

Page 7: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

NCHRP Report 673

Page 8: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

NCHRP Report 673

Page 9: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

NCHRP Report 567:Volumetric Requirements for Superpave Mix Design

• Effect of Mix Variables on Fatigue Life• For every 1% increase in in-place air voids, relative

fatigue life decreases by a nearly constant amount of about 22%.

• An increase in in-place air voids of 2% will decrease fatigue resistance by nearly 50%.

• Probably understates the importance of in-place air voids to fatigue life because it neglects the effect of changes in air voids on permeability and age hardening.

• Other analytical studies (Linden et al.) showed a predicted 10% to 30% reduction in fatigue life for every 1% increase in in-place air voids

• General rule of thumb is 10% overall reduction in performance for every 1% increase in in-place air void content.

Page 10: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

NCHRP Report 567:Volumetric Requirements for Superpave Mix Design

• Effect of Mix Variables on Fatigue Life• Relationships exist between the fatigue resistance

of asphalt mixtures and volumetric composition• Fatigue resistance increases with increasing volume of

effective binder (VBE)• assuming no change in design compaction, design air voids

and in-place air voids.• Fatigue resistance increases with increasing Ndesign

• assuming no change in VBE, design air voids and in-place air voids.

• Fatigue resistance increases with decreasing in-place air voids (increasing compaction)

• Assuming no change in VBE, design air void content, and Ndesign.

Page 11: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

NCHRP Report 567:Volumetric Requirements for Superpave Mix Design

• Effect of Mix Variables on Fatigue Life• “Although an in-depth study of the effect of in-

place air voids on pavement performance is outside the scope of this research, successful implementation of the results of this research will depend in part on achieving proper field compaction of mixtures designed according to the recommendations put forth in this report.”

Page 12: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

NCHRP Report 567:Volumetric Requirements for Superpave Mix Design

• Effect of Mix Variables on Age Hardening• Results partly confirmed a relationship between

permeability and age hardening, in that the amount of age hardening clearly increased with increasing air voids.

• The extent of age hardening also depended strongly on the specific aggregate and binder used in a mixture.

Page 13: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

NCHRP Report 567:Volumetric Requirements for Superpave Mix Design

• Effect of Mix Variables on Age Hardening• Mixture age hardening increases with increasing

air voids and decreasing aggregate specific surface.• Indicated by complex modulus• Age-hardening ratios decrease 2% to 7% for each 1%

increase in FM300 • Age-hardening ratios increase 5% to 14% for each 1%

increase in field air voids at a MAAT of 15.6°C.• Combined effect of high air voids and low aggregate

specific surface can increase age hardening by 50% or more.

• Also strongly dependent upon the specific binder used and the MAAT.

Page 14: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

NCHRP Report 567:Volumetric Requirements for Superpave Mix Design

• Effect of Mix Variables on Age Hardening• Increasing in-place air voids by 2%...

• Increases age hardening by a factor of 2 at an MAAT of 15.6°C (60°F)

• Increases age hardening by a factor of 3 at an MAAT of 23.9°C (75°F).

• Comparable with the effect of decreasing FM300 by 5%.

• Careful control of aggregate specific surface should help maintain good resistance to age hardening

• “The very high binder viscosities that can potentially exist in aged pavements could contribute significantly to surface cracking by preventing any healing from occurring at the pavement surface during hot summer weather.”

Page 15: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

NCHRP Problem #2005-D-21

“The missing link in successful long-term performance of pavements is the construction of that pavement. …even a 10% greater success ratio for the pavements being built each year would represent a savings of millions of dollars to the states and other public agencies.”

Page 16: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Perf

orm

ance

or C

ost

Initial Density

Performance or Life Expectancy

Construction Costs

Additional Equipment

Slowed Production2

1

Effect of Density on Performance

Page 17: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study

• 12.5-mm Mixture• Crushed Limestone (80-90%) and Natural Sand

(10-20%)• PG 76-22 asphalt binder

• Typical asphalt binder for interstate applications in Kentucky

• Three Asphalt Binder Contents• Optimum (4.8%)• Low (4.3%)• High (5.3%)

Page 18: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study

80,000

90,000

100,000

110,000

120,000

130,000

140,000

3 4 5 6 7 8 9 10 11 12

Fatig

ue L

ife, c

ycle

s

Air Voids, %

Effect of Percentage of Air Voids on Fatigue Life20C, 500 microstrain

Page 19: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Effect of Voids on Service Life, Nf

50

55

60

65

70

75

80

85

90

95

100

7 8 9 10 11 12

Serv

ice

Life

, Nf R

atio

Air Voids, %

Hicks (1984)

Washington State

KY Lab Density

Page 20: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study

Adair

Page 21: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study

88.4 88.888.3 88.6 89.0

88.3 87.988.6

82.8

87.1

85.186.2 86.5

86.085.1 85.3

80.0

82.0

84.0

86.0

88.0

90.0

92.0

1 5 6 7 8 9 10 11

Dens

ity, %

Location

Adair Co. KY55

Trimmed Mean

Centerline

Page 22: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study

88.4 88

.8

88.3

88.6 89

.0

88.3

87.9 88

.6

82.8

87.1

85.1 86

.2 86.5

86.0

85.1

85.3

80

82

84

86

88

90

92

1 5 6 7 8 9 10 11Location

Adair Co. KY55

Trimmed Mean

CenterlineDens

ity, %

Page 23: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study

80.0

82.0

84.0

86.0

88.0

90.0

92.0

94.0

96.0

-200 -150 -100 -50 0 50 100 150 200

Dens

ity, %

Distance from C/L, cm

Adair Co. KY55

1

5

6

7

8

9

10

11

Page 24: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study

80.0

82.0

84.0

86.0

88.0

90.0

92.0

94.0

96.0

-200 -150 -100 -50 0 50 100 150 200

Dens

ity, %

Distance from C/L, cm

Adair Co. KY55, Location 1

1

Page 25: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study

• Testing of Field Mix Samples• Assume any given sample represented the entire

project• BIG assumption, but better than sampling and testing

at every location• Compact specimens in lab (SGC) to 92% density

(8% air voids) and air voids representing average project density

• average of trimmed mean at each sampling location• Conduct rutting, fatigue, low temperature cracking

tests on each mix

Page 26: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

AMPT – Flow Number

Page 27: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

AMPT Flow Number Results(Figure from NCHRP Report 673)

Page 28: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

AMPT Flow Number

• Established standard test conditions• Unconfined• 600 kPa axial stress• 0.1-second pulse loading, 0.9-second rest period• 10,000 cycles maximum• 100 mm diameter by 150 mm height specimens• 7.0% air voids (mix design)• Test temperature equal to the average 7-day

maximum pavement temperature at a depth of 20 millimeters for the project location (the “50% Reliability” temperature in LTPPBind software Version 3.1)

Page 29: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

AMPT Flow Number: Recommended Criteria

• Recommended criteria from NCHRP Report 673

• Uses calculated Flow Number

Traffic (ESAL) Flow Number, cycles

<3 n/a

3 to <10 ≥ 53

10 to <30 ≥ 190

≥30 ≥ 740

Page 30: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study:Flow Number (Rutting)

0

100

200

300

400

500

600

700

800

900

1,000

6 8 10 12 14

Unc

onfin

ed F

low

Num

ber a

t 54C

(F

rank

en M

odel

)

Air Voids, %

KY55

KY85

KY98

US42

US60

FNProjectFN8

≈ 0.46

Page 31: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Flexural Beam Fatigue (IPC)

Page 32: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Fatigue Testing

Page 33: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Flexural Beam Fatigue Test

Page 34: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Fatigue Testing

Effect of Strain on Fatigue Life

10,000

100,000

1,000,000

10,000,000

100,000,000

0 200 400 600 800 1000Strain, x10-6

Cycl

es to

Fai

lure Criteria

93%

Page 35: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Fatigue Testing

Effect of Strain and Density on Fatigue Life

10,000

100,000

1,000,000

10,000,000

100,000,000

0 200 400 600 800 1000Strain, x10-6

Cycl

es to

Fai

lure Criteria

93%

96%

Page 36: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study:Fatigue Cycles to Failure (Cracking)

1,000

10,000

100,000

1,000,000

10,000,000

6 8 10 12 14

Cycl

es to

Fai

lure

, 20C

and

400

ms

Air Voids, %

KY55

KY85

KY98

US42

US60

Range from 30%-100%

NfProjectNf8

≈ 0.59

Page 37: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Disk-Shaped Compact Tension Test: DC(T)

Page 38: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

DC(T) Output

Crack Mouth Opening Displacement (CMOD)

Load

AREA

)(* aWBAREAGf

−=

Page 39: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

DC(T) Results: MN TH-56

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 0.2 0.4 0.6 0.8 1 1.2

Crack Mouth Opening Displacement, mm

-24°C, Top 25-mm

2000

2001

2002

2003

No Sealing

Load

, N

Page 40: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study:Fracture Energy (Cracking)

250

300

350

400

450

500

6 8 10 12 14

Frac

ture

Ene

rgy

at -1

2C, J

/m2

Air Voids, %

KY55

KY85

KY98

US42

US60

GfProjectGf8

≈ 0.87

Page 41: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study

y = -1650ln(x) + 23848R² = 0.9254

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

10,000 100,000 1,000,000 10,000,000

Tota

l Cra

ckin

g, (f

eet/

mile

)

Nf (20°C, 400 με), cycles

Page 42: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Kentucky Density Effects Study

y = -1650ln(x) + 23848R² = 0.9254

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

10,000 100,000 1,000,000 10,000,000

Tota

l Cra

ckin

g, (f

eet/

mile

)

Nf (20°C, 400 με), cycles

11.5%10.7%

13.2%

11.6%

12.9%

Page 43: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Durability and Recycled Materials

• A few words about durability and recycled materials (e.g., RAP and RAS)…

• Understand effects of materials• Adding age-hardened asphalt binder with reduced

relaxation to mix in some proportion• “The very high binder viscosities that can potentially

exist in aged pavements could contribute significantly to surface cracking by preventing any healing from occurring at the pavement surface during hot summer weather.” ~ NCHRP Report 567

Page 44: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Durability and Recycled Materials

• A few words about durability and recycled materials (e.g., RAP and RAS)…

• Understand effects of materials• Properly account for amount of recycled binder that is

available for use by the mix (i.e., how well is it actively blended?)

• Can lead to under-asphalted mixes• If using premium asphalt binders, consider impact of

added aged binder• Reduction in polymer loading?

• Mix performance testing

Page 45: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Fatigue Study: Effect of Modifier Concentration

y = 1.03E+22x-5.88E+00

R² = 9.98E-01

y = 8.69E+20x-5.60E+00

R² = 9.33E-01

y = 8.45E+20x-5.56E+00

R² = 9.93E-01

y = 1.20E+19x-5.33E+00

R² = 1.00E+001.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

300 400 500 600 700 800 900 1000 1100 1200

Cyc

les

to F

ailu

re, (

Nf)

Microstrain

ASTM 4760 4-point Flexural FatigueCycles*Stiffness Analysis

200C Test Temperature

737 Mix737 Binder748 Mix748 Binder

Page 46: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Fatigue Study: Effect of Modifier Concentration

Nf

Binder Strain (E-06)Binder 22,500 30,000 40,000 50,000737 1.61E+05 3.45E+04 7.37E+03 2.23E+03748 8.86E+04 1.91E+04 4.13E+03 1.26E+03Ratio 748/737 55% 56% 56% 57%

Nf

Mix Strain (E-06)Mixture 450 600 800 1000737 2.33E+06 5.35E+05 8.19E+04 2.25E+04748 1.61E+06 3.05E+05 4.98E+04 2.09E+04Ratio 748/737 69% 57% 61% 93%

Page 47: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Summary

• Mixture Durability• Proper materials

• Asphalt binder, aggregate, recycled materials• Proper design volumetric properties (air voids,

VMA)• Appropriate (sufficient!) design asphalt binder content• Gradation to minimize permeability

• Proper as-produced properties• Volumetric properties• Asphalt binder content• Gradation

• Proper construction• Well-compacted

Page 48: 2019 Pavements/Materials Conference - Asphalt Mixture … · 2014-12-15 · materials (e.g., RAP and RAS)… • Understand effects of materials • Adding age-hardened asphalt binder

Thanks!R. Michael (Mike) Anderson, P.E.Director of Research and Laboratory ServicesAsphalt Institute2696 Research Park Dr.Lexington, KY 40511-8480859.288.4984 office859.422.1301 [email protected]


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