Development of Standard Practice for Superpave Plus Specifications

Use of DSR and DTT in Place of ER and Ductility

Raj DongreJohn D’Angelo

Problem StatementProvide Users with alternatives to the empirical Superpave Plus tests

Elastic RecoveryDuctility/ Force DuctilityToughness and Tenacity

Approach: Develop AASHTO/ASTM Standard Practice for Superpave Plus Specifications

DTT Tcr + 3oCDSR

Multiple Stress Creep Recovery

State DOT’s Specifying Polymer PG (PG+)

ER-Elastic RecoveryFD-Force DuctilityTT-Toughness &

TenacityPA-Phase Angle

PG + modifierPG

ER

SB/SBS Required

ER & PA

PA

PA

ER

SB/SBS Required

ER & TT

ER

ER & FD

FD &ER

ER

Ductility

Ductility, TT & ER

ER &PA

ER

ER

ER

ER

FD

ERER

TT & DT

PA ER &TT

ER

Why Superpave Plus Specs.

The existing specifications do not identify the performance characteristics of modified binders.The existing specifications do not have a criteria for fatigue or durability.Agencies look to other tests to identify modifiers

Elastomeric polymer modifiers are desired

So What Do We Do? – Use DTT Approach

Use MP1A data from the DTT TestFrom the strain to failure at two MP1A temperatures

Determine strain at Tcr + 3oC For Elastomeric modifiers specify:

Strain at failure (Tcr + 3oC ) > 2.5%

Direct Tension Test

The Direct Tension Test provides a information on facture and strain tolerance of the binder.

New low temperature binder Spec. Thermal stress compared to strength

Strain at Failure vs Temperature

0123456789

1011121314151617181920

-40 -34 -28 -22 -16 -10 -4 2 8Temperature, °C

Stra

in a

t Fai

lure

, %

10/20

50/70

EVA_Modified

SBS_Modified

Superpave Plus Specifications

The Direct Tension Tester provides information on the strain tolerance and fracture properties of the binder.The strain at Tcr + 3°C can tell a lot about what is in the binder.

DT Strains by Modifier Type

PG Grade Modifier Phase Angle

Tcr Strain Tcr+3

76-23 Novophalt 82.4

75.2

63.6

73.8

66.5

87.6

79.1

79.4

-19 1.63

70-27 SBR/3% -27 3.22

82-27 SBS/4.25% -29 3.61

70-25 SBS/4% -27 3.87

76-29 SB/6% -29 3.60

70-24 - -23 1.64

70-31 EVA GRF -33 1.57

70-31 EVA -31 1.94

PCCAS Binder Study

PG Grade

Delta Original

TcrBBR

TcrDTT

Strain Tcr+3

B –1 65.7-23.8

86

74.5

86.7

-23.8 -22.8 1.27

B – 263.4-30.9

-30.9 -32.8 2.55

B – 366.1-29.7

-29.7 -30.5 2.25

Strain @ Failure for Tcr +3°C

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

-40 -34 -28 -22 -16 -10Temperature, °C

Stra

in a

t Fai

lure

, %

PG 64-22, Unmodified

B-2, 3% SBS PMA

PSR, 4% SBS PMA

Tcr + 3°C

So What Do We Do? – Use DSR Approach

Use DSR Muti Stress Creep Recovery Test

One or two creep stress levelsFour cycles per stress levelFor Elastomeric modifiers Specify:

% strain recovery > 25%

Proposed MSCR TEST ProtocolC

reep

Str

ess

time

Cre

ep

Str

ain

25 Pa

3200 Pa

1 10

time

Creep 1st cycle 70C 50 Pa

0

5

10

15

20

25

0 2 4 6 8 10 12

Time

% s

trai

n ControlElvaloyStylinkAB

Creep 1st cycle 70C 1000 Pa

0

50

100

150

200

250

300

350

400

450

0 2 4 6 8 10 12

time

% s

trai

n

controlElvaloyStylinkAB

Sample B6280, Multi-Stress (25-3200Pa) Creep Recovery Data at 70°C

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

0 200 400 600 800

Time, Sec

Stra

in, %

MTE-64-22, Multi-Stress (25-3200Pa) Creep Recovery Data Comparison

0

10000

20000

30000

40000

50000

0 200 400 600 800

Time, Sec

Stra

in, %

58°C 64°C 70°C

Plot of normalized C&R 76C Jnr = 0.1

SBS 64-40 rep 1 25Pa Creep and Recovery

0.00E+00

1.00E+00

2.00E+00

3.00E+00

4.00E+00

5.00E+00

6.00E+00

7.00E+00

0.00E+00 1.00E+01 2.00E+01 3.00E+01 4.00E+01 5.00E+01 6.00E+01 7.00E+01 8.00E+01 9.00E+01 1.00E+02

time s

stra

in %

Plot of Normalized C&R70C Jnr = 0.04

EVA 70-22 25 PA Creep and Recovery

0.00E+00

1.00E+00

2.00E+00

3.00E+00

4.00E+00

5.00E+00

6.00E+00

7.00E+00

8.00E+00

0.00E+00 1.00E+01 2.00E+01 3.00E+01 4.00E+01 5.00E+01 6.00E+01 7.00E+01 8.00E+01 9.00E+01 1.00E+02

Time S

Stra

in n

orm

al %

Plot of Normalized C&R70C Jnr = 0.6

EVA 70-22 3200 Pa Creep and Recovery

0.00E+00

5.00E+02

1.00E+03

1.50E+03

2.00E+03

2.50E+03

3.00E+03

0.00E+00 1.00E+01 2.00E+01 3.00E+01 4.00E+01 5.00E+01 6.00E+01 7.00E+01 8.00E+01 9.00E+01 1.00E+02

time s

Stra

in n

orm

al %

Findings to date

The strain at failure from the DTT does distinguish between modifiers.The DSR MSCR percent strain recovery criterion and DTT strain at failure at Tcr + 3°C can replace the FD, ER, or T&T.

Future Steps

Analyze available MP1A data and further refine the Tcr + 3oC criterionAnalyze available MSCR percent recovered strain data to develop creep stress level and test protocolWhere available, show relationships with existing ER, FD, Duct., and T&T data