Performance Grade Specifications for Emulsions Used in Pavement Preservation

Treatment

Monday, October 23, 2017 2:00-3:30PM ET

TRANSPORTATION RESEARCH BOARD

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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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