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Performance Grade Specifications for Emulsions Used in Pavement Preservation
Treatment
Monday, October 23, 2017 2:00-3:30PM ET
TRANSPORTATION RESEARCH BOARD
The Transportation Research Board has met the standards and requirements of
the Registered Continuing Education Providers Program. Credit earned on
completion of this program will be reported to RCEP. A certificate of completion
will be issued to participants that have registered and attended the entire session.
As such, it does not include content that may be deemed or construed to be an
approval or endorsement by RCEP.
Purpose
Discuss NCHRP Research Report 837. Learning Objectives
At the end of this webinar, you will be able to: • Describe emulsion and residue test methods • Describe the relationships between emulsion/residue
performance and mixture performance • Identify emulsion performance grade specifications
NCHRP Research Report 837: “Performance-Graded Specifications for Asphalt Emulsions Used in Pavement Preservation Surface Treatments” NCHRP Project 09-50
NCHRP is a State-Driven Program
– Suggest research of national interest
– Serve on oversight panels that guide the research.
• Administered by TRB in cooperation with the Federal Highway Administration.
• Sponsored by individual state DOTs who
Practical, ready-to-use results • Applied research aimed at
state DOT practitioners • Often become AASHTO
standards, specifications, guides, syntheses
• Can be applied in planning, design, construction, operations, maintenance, safety, environment
Additional NCHRP Publications Available on this Topic
• TRB’s Transportation Research Record, No. 2612: Maintenance and Preservation
• TRB’s Transportation Research Record, No. 2550: Maintenance and Preservation You can learn more about these publications by visiting www.trb.org
Today’s Speakers
• Dr. Richard Kim, Prof. NC State Univ. • Dr. Cassie Castorena, Assist. Prof. NC State • Gary Hoffman, Dir. Tech Services, PAPA
Performance Grade Specifications for Emulsions
Used in Pavement Preservation Treatment
NCHRP Project 09-50
Presented at the TRB Webinar
October 23, 2017
Y. Richard Kim, Cassie Castorena NC State University
Outline
Overview of Emulsion PG (EPG) Specification Framework
EPG Test Methods and Material Properties EPG Specification Development Recommendations for Future Research
NCHRP 09-50 Research Objective
Develop Performance-Related Specifications for PSTs (i.e., spray seal, chip seal, and slurry seal/microsurfacing) that provide a direct relationship between the key quality characteristics of asphaltic binders and PST performance.
Material Acquisition
Seven emulsion suppliers provided materials All emulsions formulated to meet the AASHTO
specifications. Standard emulsions: supplier’s typical commercial
formulations that have been used successfully in actual projects at different locations nationwide. Therefore, all standard emulsions should pass the 9-50 PG specification limits at low traffic level.
Poor Performing emulsions: emulsions modified by supplier to exhibit inferior performance compared to supplier’s standard emulsion product, while still meeting the current emulsion specification.
Emulsion List Ch
ip S
eal
C-CRS-2 (A) C-CRS-2P (A) C-HFRS-2P (A) C-CRS-1-(B) C-CRS-1H-(B) C-RS-1-(B) C-CRS-2P/L (C) C-HFRS-2 (C) C-CRS-2 (E) C-CRS-2P (E) C-CRS-2P-HP(E) C-CRS-2 (F) C-CRS-2L (F) C-CRS-2 (NC) C-CRS-2L (NC) PP-C-CRS-2 (A) PP-C-HFRS-2 (C) PP-C-CRS-2P (E)
No. of Emulsions: 18
Micr
osur
facin
g
M-CSS-1H (A) M-CSS-1H (B) M-CSS-1H (C) M-CSS-1HP (C) M-CSS-1HP (D) M-CQS-1H (E) M-CQS-1HP (E) M-CSS-1HL (F) M-CSS-1H (F) M-CSS-1HL-NC (field) PP-M-CSS-1H (F) PP-M-CSS-1HP (D) PP-M-CSS-1H (B) PP-M-CQS-1HP (E)
No. of Emulsions: 13
Spra
y Sea
l
F-CRS-2 (A) F-SS-1 (B) F-CSS-1 (B) F-Revive (E) F-SS-1H (E) F-CSS-1H (E) PP-F-CSS-1 (B) PP-F-CSS-1H (E)
No. of Emulsions: 8
EPG Specification Framework Materials are considered in two phases:
• Fresh emulsion - Constructability • Residue - Performance
Consider critical failure mechanisms for each type of surface treatment • Test methods to address specific, common distresses
in field
Retain designation for emulsifier type and set rate (e.g., RS, CRS)
Replace 1 vs. 2 viscosity designation with Emulsion Performance Grade (EPG)
EPG Framework – Cont’d
Introduce climatic considerations • Test temperatures selected based on climate
Spec limits independent of test temperature • EPG will be 3°C higher than PG
EPG grades for PG 58-22 climatic region are EPG 61-19.
Introduce traffic considerations • Different spec limits for different traffic levels • Low: 0-500 AADT; Medium: 501-2,500 AADT; High: 2,501-20,000 AADT
Example grade: CRS-EPG61-19M
PG Grades vs. EPG Grades High Temp. Grade
HMA high PG based on temp. at 20 mm depth whereas EPG based on surface temp.
About 3.9°C difference between 20 mm depth and surface
Use 3°C bump for practicality
E.g., PG 58 => EPG 61, PG 64 => EPG 67, etc.
High PG at 20 mm Depth
EPG high PG map will be identical to PG high PG map except 3°C increase!
PG Grades vs. EPG Grades Low Temp. Grade
Both HMA low PG and EPG low PG based on surface temperature
98% reliability for HMA low PG too conservative for surface treatments with shorter life => 67% reliability (one std. dev.) is used for EPG low PG
Rounding up to the nearest grade in HMA PG
Use 3°C bump for consistency Add 3°C to your current PG grades to
obtain the EPG grades for your region!
Low EPG Thresholds
Low PG Thresholds
(a)
(b)
Base Asphalt Not Affected!
Emulsion Base Asphalt
High Temp. PG High Temp. EPG
CRS-2-NC 58 67 Lowa CRS-2-F 58 61 Low CRS-2-E 58 61 Low CRS-2-A 58 61 Med
PP-CRS-2-A 58 61 Med CRS-2L-C 58 61 Med CRS-2L-F 64 67 Low
CRS-2L-NC 58 67 Med CRS-2P-A 64 67 High CRS-2P-E 58 67 High
CRS-2P-HP-E 58 67 High
0102030405060708090
100
0 1 2 3 4 5 6 7 8 9 10
% B
leed
ing
Jnr (in kPa-1)
Underlying Concept for the EPG Specification
Mix
ture
Per
form
ance
Binder Property
Target Mix Performance
Corresponding Binder Property
Using optimum EAR and AAR
EPG Test Methods
Specification Tests for Chip Seal Emulsions
MSCR
Fresh Emulsion Residue
Minimum Jnr
G* at critical phase angle
DSR Temperature- Frequency Sweep RV
Sprayability Drain-out
Storage stability (Supplier Spec)
Low Temperature Aggregate Loss
Bleeding Workability & Stability
MSCR
Fresh Emulsion Residue
Minimum Jnr
G* at Critical phase angle
DSR Temperature- Frequency Sweep RV
Mixability Storage stability (Supplier Spec)
Thermal Cracking Rutting Workability
Specification Tests for Microsurfacing Emulsions
Fresh Emulsion
Storage Stability Modified ASTM D6930
Rotational Viscometer to measure: • Separation Ratio (Rs): ηTop/ηBottom
Stability under sedimentation, creaming
• Stability Ratio (Rd): ηMixed/ηReference Potential for flocculation, coagulation
Top
Bottom
Mixed
Samples stored at high temperature
Workability Modified AASHTO TP48
Rotational Viscometer • 3-step-shear test: Vary the shear rate to simulate
spraying and drain-out potential
Drain-out
Tank to Sprayer Spraying PST
5 rpm
30 rpm
5 rpm
Residue
Residue Recovery
ASTM D7497 Method B • Best represents field aging conditions • Repeatable • Provides sufficient residue for testing
Oven @ 60°C
Cure for 6 hours
Thin film of emulsion spread on
silicone mat
Dynamic Shear Rheometer (DSR) with 25 mm Plate Use Multiple Stress Creep and Recovery (MSCR) Test
• Conducted at high temperature • 2 stress levels • Monitor non-recoverable creep compliance (Jnr) and strain
recovery – Low Jnr favorable
High Temperature Testing
DSR Frequency Sweep Test Using 8 mm Plate • Frequency sweep tests conducted at 5°C and 15°C
regardless of PG • Determine G* at the critical phase angle for the low
temperature PG
Low Temperature Testing
Specification Development Fresh Emulsion Properties
Storage Stability (Chip Seal)
( ) TopS
Bottom
Separation Ratio Rηη
=
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Sepa
ratio
n R
atio
Emulsion Number
UnmodifiedModified
Outlier
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Sepa
ratio
n R
atio
Emulsion Number
UnmodifiedModified90% Reliability95% Reliability98% Reliability
Separation Ratio >
Treatment Temperature (°C) Limit Chip Seal 60 0.5 to 1.5
Microsurfacing 25 0.2 to 1.5
Spray Seal 25 0.5 to 1.5
Fresh Emulsion Summary
Treatment Type Performance Parameter Temperature (°C) Specified Limit
Chip Seal
Separation Ratio
60
0.5 to 1.5 Stability Ratio Maximum 2 Sprayability Maximum 400 cP
Drainout Minimum 50 cP
Spray Seal
Separation Ratio
25
0.5 to 1.5 Stability Ratio Maximum 1.5 Sprayability Maximum 100 cP
Drainout Minimum 100 cP
Microsurfacing Separation Ratio
25 0.2 to 1.5
Stability Ratio Maximum 1.5 Mixability Maximum 600 cP
Specification Development Residue Binder Properties
Selected Mixture PST Tests
Chip Seal • Bleeding/Rutting – MMLS3 test • Low temperature aggregate loss – Modified Vialit test
Microsurfacing • Rutting – MMLS3 test • Low temperature cracking – Single-Edge Notched
Bending (SENB) test
High Temperature Specification Bleeding and Rutting
One Third Scale Model Mobile Loading Simulator (MMLS3)
Laboratory Chip Seal Specimen Fabrication Using ChipSS
Chip Seal MMLS3 Test Preparation
MMLS3 Bleeding and Rutting
Bleeding vs. Rutting Correlation Measured at 46°, 52°, and 58°C
y = 15.878e0.0968x
R² = 0.7745
0102030405060708090
100
0 5 10 15 20
% B
leed
ing
Rut Depth (mm)
2970 MMLS3 wheels17820 MMLS3 wheels
G*/sin delta vs. MSCR Jnr Chip Seal
0102030405060708090
100
0 10000 20000 30000 40000 50000 60000
% B
leed
ing
G*/sin delta
46C52C58C
G*/sin delta vs. MSCR Jnr Microsurfacing
0
1
2
3
4
5
0 500000 1000000 1500000
Rut
Dep
th (m
m)
G*/sin delta
46C52C58C
% Bleeding (Mixture) vs. Jnr (Binder) Chip Seals
80% Bleeding Limit in MMLS3 Test
0
20
40
60
80
100
6 8 10 12 14Aggregate Application Rate (lb/yd2)
Ble
edin
g (%
)
0.20 EAR 0.25 EAR 0.30 EAR0.35 EAR 0.40 EAR
0
20
40
60
80
100
10 12 14 16 18Aggregate Application Rate (lb/yd2)
Ble
edin
g (%
) 0.15 EAR 0.20 EAR0.25 EAR 0.30 EAR
Lightweight Aggregate Granite Aggregate
Determining MSCR Jnr Limits Chip Seals
Bleeding Limit
High Temperature EPG Limit Summary
Surface Treatment
Type PG Test Performance
Parameter Traffic Level
Test Temp. Range
EPG Limit
Chip Seal DSR MSCR
Maximum Jnr @ 3.2 kPa
Low
High
< 8 kPa-1
Med < 5.5 kPa-1
High < 3.5 kPa-1
Microsurfacing DSR MSCR
Maximum Jnr @ 3.2 kPa
Low < 5 kPa-1
Med & High < 1.5 kPa-1
Why are Jnr specification values higher for surface treatments than in HMA?
Chip seal residual binders are not aged as the HMA binders are for testing. • Aging raises the hardness of the binder and therefore
makes it more resistant to non-recoverable strains.
Low Temperature Specification Raveling for Chip Seals &
Thermal Cracking for Microsurfacings
Chip Seal Modified Vialit Test
Inverted chip seal subjected to gravity and impact. • Plate roughness, plate thickness,
and drop height modified to mitigate debonding of the sample from the plate
Aggregate loss occurred due to cohesive fracture of the binder.
PG Parameters for Low Temperature Chip Seal
05
1015202530354045
0 500 1000
Agg
rega
te L
oss
(%)
S(60) (MPa)
Unmodified
Modified
(a)
05
1015202530354045
0.00 0.20 0.40 0.60
Agg
rega
te L
oss
(%)
m(60)
Unmodified
Modified
(b)
05
1015202530354045
0 500 1000 1500
Agg
rega
te L
oss
(%)
S(8) (MPa)
Unmodified
Modified
(c)
Other Candidate Low Temp. Parameters Chip Seal
05
1015202530354045
-10.0 -5.0 0.0 5.0
Aggr
egat
e Lo
ss (%
)
∆Tc (°C)
Unmodified (-16C)Unmodified (-22C)Unmodified (-28C)Modified (-16C)Modified (-22C)Modified (-28C)
(a)(a)
CRS-2L-F
05
1015202530354045
6.5E+08 7.0E+08 7.5E+08 8.0E+08
Aggr
egat
e Lo
ss (%
)
|G*| @ δ=5° (Pa)
Unmodified (-16C)Unmodified (-22C)Unmodified (-28C)Modified (-16C)Modified (-22C)Modified (-28C)
(d)
CRS-2L-F
05
1015202530354045
0.0E+00 2.0E+07 4.0E+07
Aggr
egat
e Lo
ss (%
)
|G*|c (Pa)
Unmodified (-16C)Unmodified (-22C)Unmodified (-28C)Modified (-16C)Modified (-22C)Modified (-28C)
(c)
CRS-2L-F
05
1015202530354045
0.0E+00 1.0E+03 2.0E+03 3.0E+03
Aggr
egat
e Lo
ss (%
)
|G*|·cos2δ/sinδ @ 15°C and 0.0008 Hz (Pa)
Unmodified (-16C)Unmodified (-22C)Unmodified (-28C)Modified (-16C)Modified (-22C)Modified (-28C)
(b)
CRS-2L-F
EPG specification recommends DSR frequency sweep test using 8 mm plate • Frequency sweep tests
conducted at 5°C and 15°C regardless of PG
• Determine G* at the critical phase angle for the low temperature PG
EPG Low Temperature Testing
1.00E+04
1.00E+05
1.00E+06
1.00E+07
1.00E+08
30 40 50 60 70 80
|G*|
(Pa)
Phase Angle (°)
|G*| @ δc
δc
0
5
10
15
20
25
30
35
40
45
0.E+00 1.E+07 2.E+07 3.E+07 4.E+07 5.E+07
Aggr
egat
e Lo
ss (%
)
G* @ δ = 45⁰ (Pa)
-19-25-31
CRS-2L-F
R2 = 0.63
0
5
10
15
20
25
30
35
40
45
0.E+00 1.E+07 2.E+07 3.E+07 4.E+07 5.E+07Ag
greg
ate
Loss
(%)
G* @ δc (Pa)
-19-25-31
CRS-2L-F
R2 = 0.86
Low-Temperature Emulsion PG (°C) δc (°) -7 54
-13 51 -19 48 -25 45 -31 42 -37 39
G* at Critical δ vs. Chip Seal Aggregate Loss
Chip Seal Low Temperature Raveling Performance
05
1015202530354045
-30 -25 -20 -15 -10
Aggr
egat
e Lo
ss (%
)
Temperature (°C)
CRS-2-NCCRS-2-FCRS-2L-CCRS-2P-ACRS-2L-NCCRS-2L-F
LowMediumHigh
Chip Seal G* at Critical δ Limits to Address Raveling at Low Temperature
0
5
10
15
20
25
30
35
40
45
0.E+00 1.E+07 2.E+07 3.E+07 4.E+07 5.E+07
Aggr
egat
e Lo
ss (%
)
G* @ δc (Pa)
CRS-2-NCCRS-2-FCRS-2L-CCRS-2P-ACRS-2L-NCCRS-2L-F
Low Traffic TresholdMedium Traffic TresholdHigh Traffic Threshold
Microsurfacing G* at Critical δ Limit to Address Thermal Cracking
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
0.0035
-30 -25 -20 -15 -10
Frac
ture
Ene
rgy
(J)
Temperature (⁰C)
CSS-1H-CCSS-1HL-FCQS-1HP-ECQS-1H-ECSS-1HP-D
R² = 0.852
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
0.0035
0.E+00 1.E+07 2.E+07 3.E+07 4.E+07
Frac
ture
Ene
rgy
(J)
|G*| @ δc (Pa)
-16C (Delta = 47)-22C (Delta = 45)-28C (Delta = 43)
(b)(a)
Steel Base
Cutting Saw
Supporting Steel Frame
Beam Specimen
Low Temperature EPG Limit Summary
Surface Treatment
Type PG Test Performance
Parameter Traffic Level
Test Temp. Range
EPG Limit
Chip Seal DSR
Frequency Sweep
Maximum |G*| @δc
Low
5°C and 15°C
< 30 MPa
Med < 20 MPa
High < 10 MPa
Microsurfacing DSR
Frequency Sweep
Maximum |G*| @δc
All Traffic Levels
< 16 MPa
Raveling resistance at intermediate temperatures should be assessed during mix design.
EPG on Chip Seal Emulsions
Fresh Emulsion
EPG on Chip Seal Emulsions Residue
Recommendations for Future Research
Long Term Aging Study
Long-Term Field Validation Study
Acknowledgment
Funded by NCHRP Team Members
• NCSU: Javon Adams, Mohammad Ilias • Univ. of Wisconsin-Madison: Hussain Bahia, Preeda
Chaturabong, Andrew Hanz, Petrina T. Johannes
Questions?
Today’s Participants
• Gary Hoffman, Pennsylvania Asphalt Pavement Association, gary@pa-asphalt.org
• Y. Richard Kim, North Carolina State University, kim@ncsu.edu
• Cassie Castorena, North Carolina State University, cahintz@ncsu.edu
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