Asphalt Institute DSR-PAV TFOutcomes & Recommendation

June 18, 2019

Pavel Kriz (Imperial Oil/ExxonMobil)

Gerry Reinke (Mathy)

Mike Anderson (Asphalt Institute)

Background & Case for Action

• DSR-PAV is (after DTT) the most variable test SuperPave™

0

5

10

15

20

25

30

35

40

45

DSR (PAV) AVIS60(RTFO)

FLASH DSR(RTFO)

STIFFNESS DSR(original)

DVIS135 M-VALUE TCE SOL

d2

s%

Range of Acceptable Results, d2s%

PAV Residue

Background & Case for Action

• High test variability = poor performance discrimination

Multiple SamplesOne QC Sample

Background & Case for Action

• DSR-PAV cannot discriminate poor performing binders, namely phase instable binders exhibiting high rates of cracking.

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

Coating roofing grades

BURA III

Air-rectified paving

Straight-run PG

5000 kPa

Data from: P. Kriz, et al, Rheological Properties of Simple Bitumen, E&E Congress, Istanbul, Turkey, 2012.

TF Objectives

1. Modify T315 test protocol to reduce the test variability to acceptable level

2. Review scientific validity of DSR-PAV parameter |G*|sin δ to assess binder performance

3. Review ability of DSR-PAV test to discriminate poor performers

TF Approaches

1. Two round robins conducted• Stage 1 – thermal equilibrium time

• Stage 2 – optimal plate size & strain level

2. |G*|sin δ was analyzed for scientific validity

3. Ability of DSR-PAV parameter to discriminate poor performers was tested on 40 binders covering wide range of properties & compositions

Findings 1: Test Setup

• 25mm@0.1% strain test improved inter-lab repeatability

• When all labs were considered, data were more dispersed

• Test setup improvements are not viable

Sample

Geometry

Lab Number

NC-

DN

C-B

8mm

25mm

8 mm

25m

m

L9L7L6L5L17

L16

L12

L11

L10L9L7L6L5L1

7L1

6L1

2L1

1L1

0L9L7L6L5L17

L16

L12

L11

L10L9L7L6L5L1

7L1

6L1

2L1

1L1

0

300

250

200

1 50

1 00

50

0

Sta

nd

ard

De

via

tio

n o

f |G

*|si

n d

elt

a T

Hig

h

25mm

8mm

Geometry

Chart of Stdev( |G*|sin delta T High )

25 mm

8mm

Lower=better

Phase Angle Discriminates Properties

NC-DNC-B

56

52

48

44

40

NC-DNC-B

56

52

48

44

40

0.1 %, 25mm

Sample

de

lta

T H

igh

0.1 %, 8mm

1 .0%, 25mm 1 .0%, 8mm

NC-B

NC-D

Sample

Individual Value Plot of delta T High

Panel variables: Strain, Geometry

NC-DNC-B

56

52

48

44

40

NC-DNC-B

56

52

48

44

40

0.1 %, 25mm

Sample

de

lta

T H

igh

0.1 %, 8mm

1 .0%, 25mm 1 .0%, 8mm

NC-B

NC-D

Sample

Individual Value Plot of delta T High

Panel variables: Strain, Geometry

Phase Angle |G*|sin d

Findings 2: Science Behind DSR-PAV

• Limiting |G*|sin δ (= G’’) to a maximum limit is benefiting low phase angle, i.e. brittle binders

• High quality ductile binders with high phase angle are disadvantaged.

1 2

low phase angle = brittlehigh phase angle = ductile

𝐺1∗ = 𝐺2

∗𝐺′′ 𝐺′′

𝐺′ 𝐺′

5000 kPa

Two binders, same complex modulus, different phase angle

PASS

FAIL

in M320 fail in M320 pass

𝛿 𝛿

Findings 3: DSR-PAV vs. Binder Performance

• Phase instability is demonstrated in more negative delta Tc, higher aging index & lower phase angle

• These parameters are directly correlated to performance as they represent aging & relaxation rates; critical parameters when cracking is considered

• |G*|sin δ parameter was found not to correlate with any of these parameters, in contrary all samples passed |G*|sin δ limit of 5000 kPa

Phase Angle vs. Aging Rate• All samples passed DSR-PAV for their respective PG

Phase Angle vs. delta Tc (relaxation)• All samples passed DSR-PAV for their respective PG

DSR-PAV TF Recommendations

• Do not alter current AASHTO T315 test protocol

• Specify a parameter at intermediate temperature other than |G*|sin δ.

• Support phase angle minimum limit at constant complex modulus value to replace |G*|sin δ. • This approach utilizes correct science

• Discriminates poor performers

• Is practical – uses existing test protocol, labs are familiar with testing & historical data for comparison & validation exist. Best “speed to market” vs. other proposals

AI TAC Recommendation

AI TAC supports changes to AASHTO M320 and M332 (S-grade) to allow binders with DSR-PAV |G*|sin 𝜹parameter between 5001 - 6000 kPa (as for H, V, E grades), if their phase angle at the intermediate PG temperature is higher than 42 degrees to rectify an impact of a highly variable DSR-PAV test.

AI TAC supports industry efforts to replace |G*|sin 𝜹parameter with a more repeatable and scientifically correct parameter

Appendix

Supporting Data Objective 1

1. Thermal Equilibrium is not a significant factor in DSR-PAV variability, however DSR manufacturers should further research it

Thermal Equilibrium

0

5

10

15

20

25

30

35

40

45

0

5000

10000

15000

20000

25000

30000

1 10

Tem

pe

ratu

re (

°C)

|G*|

(kP

a)

Time (min)

te +5min +10min

24 MPa25.1 MPa

+4.6%

|G*|

1. Thermal Equilibrium is not a significant factor in DSR-PAV variability, however DSR manufacturers should further research it

Thermal Equilibrium

0

5

10

15

20

25

30

35

40

45

0

10

20

30

40

50

60

70

80

90

1 10

Tem

pe

ratu

re (

°C)

δ(°

)

Time (min)

te +5min +10min

36.1° 35.6°

−1.4%

δ

1. Thermal Equilibrium is not a significant factor in DSR-PAV variability, however DSR manufacturers should further research it

Thermal Equilibrium2

5 m

m

19 °C

010002000300040005000600070008000

0 10 20 30

|G*|

sin

de

lta,

kP

a

Time After Reaching Temperature within 0.1°C, min

Manufacturer 1Manufacturer 2Manufacturer 310 min

9.4 kPa/min

0

20

40

60

80

100

0 10 20 30

|G*|

sin

de

lta,

kP

a

Time After Reaching Temperature within 0.1°C, min

Manufacturer 1Manufacturer 2Manufacturer 310 min2

5 m

m

13 °C

NC-D Asphalt Cannon Standard

Supporting Data Objective 2

Complex, Storage & Loss Moduli

21

0

Str

ain

, 𝜸

𝝅 𝟐𝝅𝟑𝟐𝝅𝟏

𝟐𝝅

Str

es

s, 𝝈

𝜎 = 𝜎0 sin 𝜔𝑡 + 𝛿

𝛿

𝜎0𝛾0

𝑇 = period in s

Time, 𝒕

𝜔 =2𝜋

𝑇= 2𝜋𝑓 (analogous to 𝛾)

ℜ

ℑ

𝛿

𝐺′′

𝐺′

symbol modulus energy response

𝐺′ storage stored elastic

𝐺′′ loss dissipated viscous

(𝝈 in phase with 𝜸)elastic

(𝝈 out of phase 𝜸)viscous

𝑮∗ = 𝐺′ + 𝑖𝐺′′

𝑮∗ = 𝐺′2 + 𝐺′′2 =𝜎0𝛾0

tan 𝛿 = 𝐺′′ 𝐺′

𝜎 = 𝜎0 cos 𝛿 sin𝜔𝑡 + 𝜎0 sin 𝛿 cos𝜔𝑡

𝝈 in phase with 𝜸 𝝈 out of phase with 𝜸

𝜎 = 𝛾0𝜎0𝛾0

cos 𝛿 sin𝜔𝑡 +𝜎0𝛾0

sin 𝛿 co𝑠 𝜔𝑡

𝐺′ 𝐺′′

Representation in Complex Plane

Science Behind DSR-PAV

𝛿

𝐺′′

𝐺′

𝑮∗ = 𝐺′ + 𝑖𝐺′′

𝑮∗ = 𝐺′2 + 𝐺′′2 =𝜎0𝛾0

tan 𝛿 = 𝐺′′ 𝐺′

𝑮∗ ∙ sin 𝜹 = 𝑮∗𝐺′′

𝑮∗ = 𝐺′′

1 2

low phase angle = brittlehigh phase angle = ductile

𝐺1′′ = 𝐺2

′′

𝐺′′ 𝐺′′

𝐺′ 𝐺′

5000 kPa

3 4

low phase angle = brittlehigh phase angle = ductile

𝐺1∗ = 𝐺2

∗

𝐺′′ 𝐺′′

𝐺′ 𝐺′

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

Ph

ase

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.