dsr-pav tf update etg meeting · wes cooper (asphalt institute) david anderson (consultant) 1....
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DSR-PAV TF UpdateETG Meeting
May 2018
Pavel Kriz (Imperial Oil/ExxonMobil)Gerry Reinke (Mathy)
Mike Anderson (Asphalt Institute)Wes Cooper (Asphalt Institute)David Anderson (Consultant)
1. Stage 1 Completed DSR equilibrium time • Time to equilibrium is not controlled among different DSRs the same,
however its impact on data variability is not dominant
2. Stage 2 Completed effect of strain magnitude & plate size on variability • Modified test setup did not result in desired improvement in test
variability – precision improved, however accuracy worsen
• Current DSR-PAV test is not discriminatory to varying binder qualities, yet it is a limiting specification
• Phase angle showed as very reliable parameter any lab can measure, and which can discriminate asphalts and temperature changes
• Data fully support current efforts on finding an alternate property (NCHRP 09-59 and 09-60)
Reconnect from September 2017
NC-DNC-B
3.65
3.60
3.55
3.50
3.45
NC-DNC-B
3.65
3.60
3.55
3.50
3.45
25mm, 0.1%
Sample
Log
|G*|
sind
, T h
igh,
Pa
25mm, 1.0%
8mm, 0.1% 8mm, 1.0%
Individual Value Plot of Log |G*|sind, T high, Pa
Panel variables: Geometry, Strain
|G*| is a very unreliable measurement
Phase Angle is a very reliable measurement
NC-DNC-B
5652484440
NC-DNC-B
5652484440
0.1 %, 25mm
Sample
delta
T H
igh
0.1 %, 8mm
1 .0%, 25mm 1 .0%, 8mm
NC-BNC-D
Sample
Individual Value Plot of delta T High
Panel variables: Strain, Geometry
Complex, Storage & Loss Moduli
5
0
Stra
in, 𝜸𝜸
𝝅𝝅 𝟐𝟐𝝅𝝅𝟑𝟑𝟐𝟐𝝅𝝅
𝟏𝟏𝟐𝟐𝝅𝝅
Stre
ss, 𝝈𝝈
𝜎𝜎 = 𝜎𝜎0 sin 𝜔𝜔𝑡𝑡 + 𝛿𝛿
𝛿𝛿
𝜎𝜎0𝛾𝛾0
𝑇𝑇 = period in s
Time, 𝒕𝒕
𝜔𝜔 = 2𝜋𝜋𝑇𝑇
= 2𝜋𝜋𝜋𝜋 (analogous to �̇�𝛾) ℜ
ℑ
𝛿𝛿𝐺𝐺𝐺𝐺
𝐺𝐺𝐺
symbol modulus energy response𝐺𝐺𝐺 storage stored elastic𝐺𝐺𝐺𝐺 loss dissipated viscous
(𝝈𝝈 in phase with 𝜸𝜸)elastic
(𝝈𝝈 out of phase 𝜸𝜸)viscous
𝑮𝑮∗ = 𝐺𝐺′ + 𝑖𝑖𝐺𝐺′′
𝑮𝑮∗ = 𝐺𝐺𝐺2 + 𝐺𝐺𝐺𝐺2 =𝜎𝜎0𝛾𝛾0
tan 𝛿𝛿 = ⁄𝐺𝐺𝐺𝐺 𝐺𝐺𝐺
𝜎𝜎 = 𝜎𝜎0 cos 𝛿𝛿 sin𝜔𝜔𝑡𝑡 + 𝜎𝜎0 sin 𝛿𝛿 cos𝜔𝜔𝑡𝑡
𝝈𝝈 in phase with 𝜸𝜸 𝝈𝝈 out of phase with 𝜸𝜸
𝜎𝜎 = 𝛾𝛾0𝜎𝜎0𝛾𝛾0
cos𝛿𝛿 sin𝜔𝜔𝑡𝑡 +𝜎𝜎0𝛾𝛾0
sin 𝛿𝛿 co𝑠𝑠 𝜔𝜔𝑡𝑡
𝐺𝐺𝐺 𝐺𝐺𝐺𝐺
Representation in Complex Plane
Science Behind DSR-PAV
𝛿𝛿𝐺𝐺𝐺𝐺
𝐺𝐺𝐺
𝑮𝑮∗ = 𝐺𝐺′ + 𝑖𝑖𝐺𝐺′′
𝑮𝑮∗ = 𝐺𝐺𝐺2 + 𝐺𝐺𝐺𝐺2 =𝜎𝜎0𝛾𝛾0
tan 𝛿𝛿 = ⁄𝐺𝐺𝐺𝐺 𝐺𝐺𝐺
𝑮𝑮∗ � sin𝜹𝜹 = 𝑮𝑮∗𝐺𝐺′′
𝑮𝑮∗ = 𝐺𝐺𝐺𝐺
1 2
low phase angle = brittlehigh phase angle = ductile
𝐺𝐺1′′ = 𝐺𝐺2′′𝐺𝐺′′ 𝐺𝐺′′
𝐺𝐺𝐺 𝐺𝐺𝐺
5000 kPa
3 4
low phase angle = brittlehigh phase angle = ductile
𝐺𝐺1∗ = 𝐺𝐺2∗𝐺𝐺′′ 𝐺𝐺′′
𝐺𝐺𝐺 𝐺𝐺𝐺
5000 kPa
DSR-PAV can not capture fundamental differences
0
1
2
3
4
5
6
7
8
9
-40 -20 0 20 40 60 80 100 120 140 160
log(
|G*|
.sin
δ),
Pa
Temperature, deg C
0
10
20
30
40
50
60
70
80
90
100
-40 -20 0 20 40 60 80 100 120 140 160
Phas
e An
gle,
deg
Temperature, deg C
Coating grades
BURA IIIAir-rectified paving
Straight run PG & RAF Coating grades
BURA IIIAir-rectified paving
Straight run PG & RAF5000 kPa
• Two asphalts (PG 64 & PG 46) were oxidized to variety of products ranging from 1 PG stiffer paving grade to roofing coating grades
• Phase angle offers clear differentiation between these binders
Data from: P. Kriz, et al, Rheological Properties of Simple Bitumen, E&E Congress, Istanbul, Turkey, 2012.
Colloidal Stability & Aging Index
• Set of samples of varying phase stability prepared in the lab (by adding oil, asphaltenes, oxidation)
• Are ΔTc, phase angle & aging susceptibility related to colloidal stability?
0-5-10-15-20-25-30
60
50
40
30
20
Delta Tc
Phas
e An
gle
at D
SRPT
16-1919-2222-2525+below 16
=5000 kPaT at |G*|sind
12108642
60
50
40
30
20
RTFO Vis Ratio
Phas
e An
gle
at D
SRPT
16-1919-2222-2525+below 16
=5000 kPaT at |G*|sind
The Proposal
• Short term: Allow good asphalts in the specification• For asphalts tested above G”>5000 kPa, review phase angle• If phase angle is sufficiently high (e.g. above XX degrees)
allow them to pass• TF needs help to collect data – field performance & phase
angle at intermediate temp. volunteers?
• Long term: develop a new fatigue parameter to limit fast aging materials and poor phase stable materials (e.g. NCHRP, D. Christensen)
• There were reasons for aging index & ductility in the specification – Superpave already measures these properties
Science Behind DSR-PAV, cont’d
Temp or time
log |G*|δ (phase angle)Max limit on
“creep stiffness”
Low T PG
S(t) promotes lower stiffness, m-val more ductile binder to prevent cracking
High T PG
|G*|/sin delta - Promotes higher stiffness &More elastic binders to prevent rutting
Intermediate PG|G*| sin delta promotes less viscous, more elastic (i.e. more brittle) binders? Does this makes sense?
Better binder
Poorer binder
Test Setup - Conclusion
• Very large variability for modulus measurement• Data from 3 labs had to be excluded from analysis• Variability increases with increasing stiffness• 25mm PP at 0.1% showed lower variability for
individual labs however larger dispersion among labs
25 mm 8mm
COV for Phase Angle about 10x lower
COV Delta, %COV |G*|sin delta, %NC-DNC-BNC-DNC-B
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
COV,
%
NC-BNC-D
Sample_1
Chart of COV |G*|sin delta, %, COV Delta, %
Phase Angle Measurement is Less Variable
Over a narrow range of temperature, G’ & G’’ change relatively proportionally, thus a change in phase angle would be much less significant than a change in |G*|
G’
G’’
δ
𝐺𝐺∗ � sin 𝛿𝛿 = 𝐺𝐺𝐺𝐺
• 5000 kPa limit suggested on very limited data developed from tests on asphalts used in the Zaca-Wigmore Test Road1
• Deacon et al.2 showed that a general trend between G” & fatigue can only be observed when material properties are vastly different (2 – 18 MPa)
Limit Increase
5MPa6MPa
5MPa6MPa
1Anderson, D.A. and T.W. Kennedy, “Development of SHRP Binder Specification”, J AAPT, Vol. 62, 1993, pp. 481-507.2A.A. Tayebali et al., “Fatigue Response of Asphalt-Aggregate Mixes”, SHRP-A-404, National Research Council, Washington, DC, 1994.
Change to 6 MPa is NEGLIGIBLE with respect to mix data