viewing cracking through a black space telescope€¦ · viewing cracking through a black space...
TRANSCRIPT
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 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 )
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
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 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