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Advances in performance evaluation of asphalt binders
Road MaterialsandPavementDesign
Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
Hussain U Bahia
Professor
University of Wisconsin, USA
March 25, Lisbon, Potugal
Road MaterialsandPavementDesign
Outline
>Performance grading (PG) background
>PG plus in USA
>New Concept:Damage Resistance Characteriztaion
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
�Rutting Resistance o Multiple Stress Creep and Recovery
�Fatigue Resistance o Binder Yield Energy Test
o Linear Amplitude Sweep
�Bond strength- cohesion and adhesion
�Fracture Testing
Road MaterialsandPavementDesign
Cold Temp.Cracking
Fatigue Cracking Rutting
Mixing &Paving
Performance Grading and Modified (Engineered) Bitumen
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 20103
Temperature
Typical Asphalt
Ideal (modified) Asphalt
Stiffn
ess, G
*
PMB
WMA
Superpave Bitumen Tests
DSR
Dynamic Shear
DT
Related to Performance!
• Climate -- PG HT-LT
• Traffic Speed – DSR
• Traffic Volume – PG shift
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
RV
RotationalViscometer
Dynamic Shear Rheometer
BBR
Bending Beam Rheometer
Direct Tension Test
• Traffic Volume – PG shift
• Traffic loading – NA
• Pavement Structure – NA
• Assumption:
Bitumen in Linear VE
range
Road MaterialsandPavementDesign
The focus on Linear Visco-elasticity: G*, delta
1E+04
1E+05
1E+06
Co
mp
lex
Mo
du
lus
(P
a)
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
1E+00
1E+01
1E+02
1E+03
1E+04
45505560657075808590
Co
mp
lex
Mo
du
lus
(P
a)
<< Viscous Phase Angle delta (°) Elastic >>
Low SBS %
No polymer network
Viscous above 60°C
Reasonably workable
High SBS %
Polymer network
Elastic during compaction
Workability problem
Courtesy of
Nynas
Road MaterialsandPavementDesign
Performance Grading –Redefined (2001)
>Linear VE is not
sufficient (NCHRP 9-10)
>Bitumen damage resistance
σf
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
is very important
>Modified bitumen are best
in damage resistance
Strain εf
LVE
Non-Linear
-- Damage
Evolution of PG Bitumen Specification P
erfo
rma
nce
In
dic
ato
rs
S, m, Tg, Fracture Energy
Nf
Adhesion
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
Per
form
an
ce I
nd
ica
tors
Jnr
Temperature
Tmin Tavg Tmax
η= 3.0 η= 3.0 η= 3.0 η= 3.0 pa-s
135 C 160 C
ηι= 6.0 ηι= 6.0 ηι= 6.0 ηι= 6.0 pa-sJnr
Adhesion
Current Test: Cyclic Loading
-10000
0
10000
20000
30000
40000 Strain 2%
Strain 25%
Strain 50%
Stress/Stress/
StrainStrain
γγγγγγγγ22
ττττττττ22
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 20108
-40000
-30000
-20000
-20000 -10000 0 10000 20000
Torque (stress)
Can only give total energy:
Total W= π .τi2 .sin δ/ G*
= Welastic+ Wdelayed elastic+ Wviscous
The new tests : Creep and Recovery (MSCR)
DSR 0.1
68
Shear Stress, kPa
0.7 1.4
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
DSR
Dynamic Shear Rheometer
0.1 0.7 1.4
0.1
Shear Stain, mm/mm
0.7 1.4
Accumulated Strain
Binders with same G*/sinδ but different recovery
10%
12%
14%
PG82- Oxidized (1 cycle)
PG82 - Oxdized (100 cycle)
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
0%
2%
4%
6%
8%
0 2 4 6 8 10 12
Time (s)
Str
ain
PG82-SBSr (1 cycle)
PG82- PEs (1 cycle)
PG82-SBr (100 cycle)
PG82-PEs (100 cycle)
Road MaterialsandPavementDesign
Binder Rutting Parameter
>The creep compliance, J(t), in terms of itselastic component (Je), the delayed-elastic(Jde), and the viscous component (Jnr):
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 201011
>Calculate the viscous compliance (Jnr).
vdee JJJtJ ++=)( nr
Road MaterialsandPavementDesign
Binder Fatigue Data
1,E+07
1,E+08
Dy
na
mic
Sh
ea
r M
od
ulu
s [P
a]
Time Sweep - 5% Applied StrainALF Control
ALF CR-TB
ALF Terpolymer
ALF SBS-LG
TPF Control A
TPF PG64-34 A
TPF PG76-22 A
TPF PPA A
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
1,E+05
1,E+06
1,E+07
1,E+01 1,E+02 1,E+03 1,E+04 1,E+05
Dy
na
mic
Sh
ea
r M
od
ulu
s [P
a]
Time (Cycles/Frequency) [sec]
TPF PPA A
TPF Latex A
AASHTO Standard for Binder Yield Energy (BYE)
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
Yield Energy Evaluation of different binders
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
Road MaterialsandPavementDesign
Linear Amplitude Sweep (LAS)Need 2 tests for VECD analysis
15
20
25
Ap
pli
ed
Str
ain
[%
]
Amplitude Sweep Loading Scheme
1,E+05
1,E+06
Sh
ea
r R
ela
xati
on
Mo
du
lus
[Pa
]
Stress Relaxation Test Results
+
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
0
5
10
0 500 1.000 1.500 2.000 2.500
Ap
pli
ed
Str
ain
[%
]
Loading Cycles
1,E+03
1,E+04
1 10 100 1000
Sh
ea
r R
ela
xati
on
Mo
du
lus
[Pa
]
Time [s]
+
Relaxation /freq Sweep Amplitude Sweep
Road MaterialsandPavementDesign
AASHTO Draft Procedure
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
Road MaterialsandPavementDesign
VECD Analysis of LAS – Damage Curve
Damage equation following Yong-Rak Kim & D. Little work (2006):0,60
0,80
1,00
No
rma
lize
d |G*
|si
n δδ δδ
LAS VECD Analysis
64-28 SBS
64-34 ELV
58-34 ELV
64-28 NEAT
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
( )[ ] ( ) αα
α
δδγπ +−
=
+− −−⋅⋅≅∑ 1
1
1
1
11
2
0 sin*sin*)( ii
N
i
iiD ttGGItD
0,00
0,20
0,40
0 1.000 2.000 3.000 4.000 5.000
No
rma
lize
d |
Damage Intensity
Road MaterialsandPavementDesign
VECD Fatigue Prediction Model
>With the VECD curve fit to a simple numeric equation:
>Fatigue life can be predicted using:
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
>Fatigue life can be predicted using:
k = 1 + (1 – C2)α
Road MaterialsandPavementDesign
Simulated Fatigue
1,E-02
1,E-01
1,E+00
1,E+01
Nf / ESAL's
Fatigue Law: Nf = A(γ0)B
[Traffic Volume
A
B
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
1,E-05
1,E-04
1,E-03
1,E-02
1 10
Nf / ESAL's
Applied Shear Strain [%][Pavement Structure Indicator]
[Traffic Volume
Indicator]
Road MaterialsandPavementDesign
[Nf/ESAL’s]
Pavement Structure:Weak(400µε)
Strong(200µε)
Binder Qualification ExampleEffects of Traffic and Pavement Structure
>For unmodified PG70-22 binder, Nf = A×(γ0)B
�A: 3.89 × 106
�B: -5.277
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
Pavement Structure:Weak(400µε)
Strong(200µε)
Traffic[ESAL’s]
(S) 1,000,000
0.10 3.86
(H) 3,000,000
0.03 1.29
(VH) 10,000,000
0.01 0.39
PG70-22 H
Modified BBR to Test for Fracture
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
FEM simulations of two different geometries New BBR Geometry:
=>Continuity of stresses
=>Plane sections remain
plane after bending
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
plane after bending
SENB Example Results
15000
20000
25000
30000
35000
Lo
ad
(m
N)
Sample 1
Sample 2
Sample 3
Sample 4
32000
36000PPS = 252
pulses/step = 2Limestone
Mastic
Binder
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
0
5000
10000
0 0.1 0.2 0.3 0.4 0.5
Displacement (mm)
Lo
ad
(m
N)
0
4000
8000
12000
16000
20000
24000
28000
0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40
Displacement (mm)
Lo
ad
(m
N)
Granite
Limestone
Constructed 27/04 and
trafficked for 1 warm day
Constructed 29/04
Temperature drop 30/04
Bitumen Adhesion
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
Source: Gerrie Van Zyl – RSA
Road MaterialsandPavementDesign
Bitumen Bond Strength Testing Apparatus
Graded Scale for Air Flow Control
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
Road MaterialsandPavementDesign
Example of Test Results
40
7
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010January 05, 2010 4
6
5
0.820
22
15
Cohesive Failure Adhesive Failure
Road MaterialsandPavementDesign
Results and Analysis:
Effect of Conditioning Time in Tap Water
2000
2500
3000
off
T
ensi
le
Str
eng
th
(KP
a)
Limestone
2000
2500
3000
off
T
ensi
le
Str
eng
th
(KP
a)
Granite
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
0
500
1000
1500
Pu
ll-o
ff T
ensi
le
Str
eng
th
(KP
a)
0 hour
6 hours
24 hours
0
500
1000
1500
Pu
ll-o
ff T
ensi
le
Str
eng
th
(KP
a)
0 hour
6 hours
24 hours
January 05, 2010 18
Road MaterialsandPavementDesign
BBS Relationship to Performance
Tensile Strength > 125 psi yield <10% chip loss. Curing time ~ 6 hours.
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
hours.
Acknowledgments
Mrs. Maria de Lurdes Antunes
Mr. Jorge Barreira de Sousa
National Civil Engineering Labs
Road Pavements: Materials, design and performance
Lisboa, LNEC, 25 March 2010
Questions
Please write to me:
Hussain U. Bahia