Viewing Cracking Through a Black Space Telescopea Black Space Telescope

WRI Pavement Performance SymposiumJuly 2011

Presentation by: Gayle King

AcknowledgementsFAA/AAPTP Project 6 1FAA/AAPTP Project 6-1 “A Laboratory and Field Investigation to

Develop Test Procedures for Predicting Non-p gload Associated Cracking of Airfield HMA Pavements” Project Manager: Monte Symons Project Manager: Monte Symons PI: Doug Hanson Mike Anderson, Phil Blankenship, Gayle King BBR Mi t e Testing Mihai Ma astean BBR Mixture Testing: Mihai Marasteanu Rheological Consultant: Geoff Rowe

Are Some SuperPave Pavements Cracking Prematurely?

H /Q YES! Hesp/Queens: YES! WRI Field Aging Study: YES! John Epps: TRB Research Needs

Discussion at AFK10: YES!

Problem at least partially due to p ypavement aging.

To prevent age-induced cracking, first understand:

Asphalt Durability

Cl i P t Claine Petersen: A durable asphalt:

1. has physical properties necessary for desired initial product performance

&&2. is resistant to change in physical

properties during long term in use properties during long-term, in-use environmental aging

Petersen, J.C., “Chemical Composition of Asphalt as Related to Asphalt Durability-State of-the-Art”, TRR. 999, 1984

Asphalt Oxidation

V ll A E b ittl tVallerga: Age-Embrittlement

l k kiRaveling Block Cracking

Asphalt OxidationPredicting Pavement Failures

MEDG Gl b l A i Eff t M d lMEDG Global Aging Effects Model Models high temp η or G* with aging No measure of low-temperature rheology No phase angle or m-value Does not appropriately consider initial

asphalt quality

Mirza, M.W. and Witczak, M.W., “Development of a Global Aging System for Short- and Long-Term Aging of Asphalt Cements”,

AAPT 1995AAPT, 1995

Asphalt DurabilityPredicting Block CrackingChallenge question:Challenge question:

Asphalt oxidation accelerates at high pavement temperatures, but does block cracking occur at lower temperatures?

If yes why not use low temperature physical If yes, why not use low temperature physical properties to predict block cracking?

Critique of Global Aging System:Christensen, D.W. and Bonaquist, R.F., “Volumetric

Requirements for SuperPave Mix Design”, NCHRP Report #567 TRB 2006 #567, TRB, 2006

WRI Aging Study - HarnsbergerArizona Field Aging

Hypothesis: Asphalts fromAsphalts from

differentcrude oil sources will sources will exhibit different field performanceperformance

Arizona Validation Site

Constructed Nov. 2001Shoulder cored Nov. 2005

2 63-mm lifts, 19-mm NMS dense graded aggregate, 4.7% AC)S ou de co ed o 005 g aded agg egate, % C)

Effect of Pavement Depth on Aged Asphalt Properties

1E+09AZ1-1, 4th Year, Shoulder

1E+07

1E+08

1E+09

Pa)

2nd Slice Bottom Slice

1E+04

1E+05

1E+06

ex M

odul

us (P

Top Slice

2nd Slice

3rd Slice

1E+01

1E+02

1E+03

Com

ple

1E+00

1E+01

1E-06 1E-04 1E-02 1E+00 1E+02 1E+04 1E+06 1E+08 1E+10

Reduced Angular Frequency (rad/s)

After Oxidation:

Top slice > 2nd slice > 3rd slice > Bottom slice

Effect of Pavement Depth on Aged

90AZ1-1, 4th Year, Shoulder

Asphalt Properties

70

80

90

3rd Slice

40

50

60

e A

ngle

(deg

)

Top Slice

3rd Slice

Bottom Slice

20

30Phas

e

2nd Slice

0

10

1E-06 1E-04 1E-02 1E+00 1E+02 1E+04 1E+06 1E+08 1E+10

Reduced Angular Frequency (rad/s)f id i

Reduced Angular Frequency (rad/s) After Oxidation:Top slice > 2nd slice > 3rd slice > Bottom slice

Comparison of m-Value & S Grades pAAS-1 & Exxon AC-20 at Various Aging Times

Poor man’s Black SpaceBlack Space

Glover, et.al. FHWA/TX-05/1872-2

Asphalt OxidationPhysical Changes - Ductility

Con ention l Wi domConventional Wisdom:

Kandhal tied block cracking severity to d l ( )ductility at 60ºF (15ºC) Loss of surface fines as ductility 10cm

f k d h d l f ll Surface cracking evident when ductility falls to 5 cm Serious surface cracking at ductility falls below 3 cm

“Low-Temperature Ductility in Relation to Pavement Performance”, ASTM STP 628, 1977

Glover’s Cracking parameter

P d ki f ti b d Proposed cracking function based on analysis of Maxwell model

Q ti G Questions: Relationship to ductility

G

Relationship to fatigue Assumption of time-temperature

superposition

G

superposition Relationship in Black Space (G* vs.

Phase Angle)g )

Ductility vs. G’/(η’/G’)

(Glover et.al. 2005)

Rowe: AAPT Prepared Discussion

GG

pSimplification of Cracking Parameter

tanGGandG

tan1'

GG

Ghence

GGG

GG

tantan

GGor

G

Gtherefore

G

Rowe: AAPT Prepared DiscussionSimplification of Cracking Parameter

P tti th ti i i l f t Putting the equation in simple format:

sincos*

tancos*

tan

2 GorGorG

Note frequency is constant sintantan

G*(Cosδ)2/sinδ x ω Only real variables are G* and fn(

fn((cos )2/sin

G*(Cosδ)2/sinδ x ω

fn((cos )2/sin Limiting value of 9E-04 MPa/sec at 0.005

rad/sec becomes…* / 8 k G* cos2/sin 180kPa

Laboratory Binder TestingExperimental Matrix

A h lt Bi d Asphalt Binders West Texas Sour (PG 64-16)

G lf S h ( G 6 22) Gulf-Southeast (PG 64-22) Western Canadian (PG 64-28)

Table 1: Asphalt Binder Testing Matrix Unaged PAV20 PAV40 PAV80 DSR Mastercurve DSR Function (Texas A&M) DSR Monotonic (Wisconsin) Ductility, 15°C Force DuctilityForce Ductility BBR DTT  

BBR: Gulf-Southeast (GSE)

-10.0

°C

-20.0

ratu

re,

°

Tc,S(60)-30.0

Tem

per Tc,S(60)

Tc,m(60)

-40.0

0 20 40 60 80

T

i iPAV Aging Time, Hrs

BBR Cracking Parameter - ΔTc

ΔT T ( ) T ( )ΔTc = Tc (m-value = 0.30) - Tc(S = 300 MPa)

Relationship to ductility Relationship to G’/(η’/G’) Relationship to G /(η /G ) Relationship to R-value (CA model)

Effect of PAV Aging Time on Tc

12.0

Difference

6.0

WTX

Between Tc,m and

0.0

WTXGSE WC

Tc,S (°C)

- 6.00 20 40 60 80

PAV Aging Time, Hrs

Relationship between G’/(η’/G’) vs Ductility

y = 0 79x + 4 6314

y = 0 82x + 1 42

y = 0.79x + 4.63R² = 0.57

10

12

ity,

cm

y = 0.82x + 1.42R² = 0.92

6

8

Du

ctili

2

4

Mastercurve

Single Point

ed

icte

d

00 2 4 6 8 10 12 14

Pre

Measured Ductility, cm

Relationship between G′/(η′/G′) and ΔTc

1E-01

1E-03

1E-02M

Pa/

s

1E-05

1E-04

1E 03

(η′/G

′), M

1E-07

1E-06

1E 05

G′/(

1E-07-6.0 -3.0 0.0 3.0 6.0 9.0 12.0

Difference Between Tc,m(60) and Tc,S(60), °CWest Texas SourGulf SoutheastWestern Canadian

Black Space Diagram: Western Canadian Asphalt Binder

1.00E+09

1.00E+08

1 00E+06

1.00E+07 OriginalPAV-20

*,

Pa

PAV-40

1.00E+05

1.00E+06

G*

PAV-80

1 00E+03

1.00E+04

1.00E+030 10 20 30 40 50 60 70 80 90

Phase Angle, degrees

Western Canadian PG 64-28

WC PG 64-28

Plot of R-values in Black Space

1.00E+08

1.00E+09

1.00E+07

Pa PAV0A i

1.00E+05

1.00E+06

G*,

P

PAV20PAV40PAV802.91

Aging

1.00E+045000 kPa2.30

2.03

1 41

R-value shown gives shape of master curve.

1.00E+030 20 40 60 80

Phase Angle, degrees

1.41

Rowe –AAPT -2011

Binder Aging StudyG* (15°C d 0 005 d/ )G  (15°C and 0.005 rad/s)

Original 20 hr PAV 40 hr PAV 80 hr PAV

WTX 98,900 1,329,000 1,495,000 5,226,000, , , , , , ,GSE 58,000 423,700 863,800 2,079,000WC 5,440 170,200 362,900 1,615,000

δ (15°C and 0.005 rad/s)

Original 20 hr PAV 40 hr PAV 80 hr PAVOriginal 20 hr PAV 40 hr PAV 80 hr PAV

WTX 77.5 55.2 53.2 38.2GSE 76.6 62.9 55.7 45.7WC 84.1 63.4 56.5 43.1

PAV Aging in Black Space

U i R V lUsing R‐ValuesG* & δ at 15°C, 0.005 rad/s

9.000

10.000

7.000

8.000

log G*WTX

GSEPASS

20 hrPAV

40 hrPAV

80 hrPAV

5.000

6.000

g(Pa)

WC

R‐value = 1

R‐value = 2

PASSBlockCracking

0 hr PAV

PAV

3.000

4.000

R‐value = 2

R‐value = 3

FAIL

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0

Phase Angle

PAV Aging in Black Space

U i G'/( '/G')Using G'/(η'/G')G* & δ at 15°C, 0.005 rad/s

7

8

40 hr

80 hrPAV6

log G*G'(n'/G') = 180 kPa

BlockCracking

20 hrPAV

40 hrPAV5

g(Pa) G'/(n'/G') =450  kPa

WTX

GSENo Block

g

0 hr PAV3

4 WCCracking

0 10 20 30 40 50 60 70 80 90

Phase Angle

PAV Aging in Black Space

U i G* i δUsing G* x sin δG* & δ at 15°C, 0.005 rad/s

8.000

9.000

FAIL

80 h6 000

7.000

log G*WTX

PASS

20 hrPAV

40 hrPAV

80 hrPAV

5.000

6.000g(Pa) GSE

WC

G*x sind = 5000 kPa

PASS

0 hr PAV

PAV

3.000

4.000 G*x sind = 1000 kPa

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0

Phase Angle

Low Temperature Mixture RheologyBBR Stiffness & m-value

B di B Rh t (BBR) Bending Beam Rheometer (BBR) Rectangular beams - standard BBR

geometry – (Marasteanu)geometry (Marasteanu) $200 tile saw cuts surface mix specimens

Condition & test in BBR at -18 to -6ºC Condition & test in BBR at 18 to 6 C

BBR Mixture TestingWest Texas Sour

l i f l i h i

0 280

Evolution of m‐value with agingWest Texas Sour Mix

Evolution of Stiffness with AgingWest Texas Sour Mix

0.2200.2400.2600.280

e

20000

25000

a)

0.1600.1800.2000.220

m‐value

‐6C10000

15000

ess  (M

pa

‐6C

0.1000.1200.140 ‐12C

0

5000

0 20 40 60

Stiffne

‐12C

0 20 40 60

Mixture Aging Time @135°C, hours

0 20 40 60

Mixture Aging Time @135°C , hours

BBR Mixture TestingGulf-Southeast

Evolution of Stiffness with AgingGulf‐Southeast Mix

Evolution of m‐value with agingGulf‐Southeast Mix

20000

25000

Mpa)

0 2200.2400.2600.280

10000

15000

ffness  (M

‐12C0.1600.1800.2000.220

m‐value

‐12C

0

5000

0 20 40 60

Stif

‐18C

0.1000.1200.140 ‐18C

0 20 40 60

Mixture Aging Time @135°, hours

0 20 40 60

Mixture Aging Time @135°C, hours

BBR Mixture TestingWestern Canadian

Evolution of Stiffness with AgingWestern Canadian Mix

20000

25000

pa)

10000

15000

tiffness (M

‐12C

0

5000

0 20 40 60

S t

‐18C

0 20 40 60

Mixture Aging Time @135°C, hours

BBR Stiffness vs. Loading TimeInversion, but no loading damage!

BBR m-value vs. Loading TimeInversion, but no loading damage!

Using Hirsh Model &Shenoy Critical Cracking Theory

Cooling Rate Impact on Critical Cracking Temperature

16

18

g p g pWestern Canadian - 48 hour mix aging

C li R t

Thermal 10

12

14 1 degree/hour10degrees/hourTC-1 degree/hour

Cooling Rate

Stress (MPa)

6

8

10 TC 1 degree/hourTC-10 degree/hour

2

4

Temperature (ºC)

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

BBR Mixture Bending Test: Impact of Aging & Cooling Rate on

00 10 20 30 40 50 60

Critical Cracking Temp

-5

0

Critical Cracking

WTS -1C/hr

-15

-10Cracking

Temperature, °C

WTS -10C/hrG-S -1C/hrG-S -10C/hrWC 1C/hr

25

-20

WC -1C/hrWC -10C/hr

C l i C li l i -30

-25

Mix Aging Time @135°C - hours

Conclusion: Cooling rate less important as materials age

Hypothesis for:Cracking at Low Temperatures Thermal Cracking Thermal Cracking

Driven by Thermal Shrinkage Stresses on Cooling Primary Function: Low Temp. Binder Stiffness

Block Cracking Driven by Curling Stresses from Temperature & Stiffness

GradientsGradients Primary Function: ΔTc (decreasing phase angle) Crack-Initiation Temp increases with oxidation:

i ‘ l ’ d S h l Decreasing BBR ‘m-value’ and DSR phase angle Decreasing DTT failure strain Decreasing R-value Decreasing Fracture energy

Conclusions

Black Space Diagrams can be used to Black Space Diagrams can be used to compare cracking parameters and select preferred failure criteria.p

ΔTc and G*x(cosδ)2/sinδ)xω correlate closely with ductility for unmodified asphalts.

Failure curves using R-value do not correlate well with ductility nor the other two parameters (ΔTc & Glover)parameters (ΔTc & Glover)

Microcracking can occur as aged mixtures cool (m<0 12; S>20 000 Mpa)cool (m<0.12; S>20,000 Mpa)

Research Needs

E i t l ff t d l Environmental effects models Predict rate of oxidative aging

di i i i i f bl k ki Predict initiation of block cracking

Tools to optimize timing strategies for t tipavement preservation

Performance specifications Binder purchase specifications Use of RAP and asphalt shingles

Asphalt Durability

Don’t forget the Don t forget the oxidation oxidation

chemistry!chemistry!

Asphalt Oxidation ChemistryThe Products

Petersen, Mill, Greene

Oxidation Products Carbonyls form in three steps: Ketones C b li A id Ald h d Carboxylic Acids, Aldehydes Acid anhydrides

Sulfoxides; Disulfoxides Sulfoxides; Disulfoxides

For evolving rheology, carbonyls matter, sulfoxides don’t!sulfoxides don t!

What about further aromatization?

Asphalt Oxidation ChemistryThe KineticsPetersen (WRI) Van Gooswilligen Mill GloverPetersen (WRI), Van Gooswilligen, Mill, Glover

Oxidation Kinetics Temperature dependence

G* & Carbonyl follow Arrhenius (exp (1/T) Evolving rheology at low temperature: S fairly stable, m-

value drops rapidly

Pressure dependence - exponential Defined rate determining step (Bitumen, O2, catalyst) Classic phenols inhibitors don’t workClassic phenols inhibitors don t work Identified reaction inhibitors (Azide, CN-)

Auto-oxidation doesn’t fit kinetics!

Asphalt Oxidation ChemistryThe MechanismsWRI/GloverWRI/Glover

Dual Carbonyl Oxidation Mechanisms 2 ti t b th 1 t d i 2 reaction rates – both 1st order in

bitumen One fast but slows or stops with time One fast, but slows or stops with time

Indole/Carbazol condensations (see fuels oxidation work by Pedley/Hiley, Mushrush, Harrison, Beaver)

One slow, but continues indefinitely Non-porphoryrin organometallic catalysts Vanadyl Acetyl-Acetonate – Branthaver/Tort Manganese complexes - Chemcrete Manganese complexes - Chemcrete

The MechanismsN-ETIO OxycyclicsKing/BeaverKing/Beaver

N-ETIO – Electron Transfer Initiated OxidationOxidation For indole condensations, two electron transfers

occur before rate determining step (Beaver) Rate-determining step is initiated by a forbidden

triplet-to-singlet electron spin flip (King) Oxycyclics explain the rate determining step Oxycyclics explain the rate determining step,

Petersen’s carbonyl products (even anhydrides), and the influence of catalysts (King)

Cl i i hibit ( ti id t ) d ’t k Classic inhibitors (anti-oxidants) don’t work N-ETIO Oxycyclics fit both (dual) mechanisms

Thank You. Questions?Q