UPDATE3rd Generation ABCD:

-Repeatability-Validation

Sang-Soo Kim

TRB Superpave Binder ETGMadison, WIJuly 20, 2005

2

ScopeScope

• 3 rd Generation ABCD• Validation with Elk County, PA Sample (1976)

– Six AC-20s

3

ABCD DevelopmentABCD Development

• Earlier ABCD (1st Generation)– Aluminum Mold & Aluminum Ring– Round Specimen– 30 min Conditioning at -20C; Cooling Rate = 10C/hr

• 2nd Generation– Silicone Mold & Invar Ring– Two Holes in Specimen– 30 min Conditioning at -20C; Cooling Rate = 10C/hr

• 3rd Generation– Silicone Mold & Invar Ring with Biaxial Strain Gauge & RTD– One Hole in Specimen– 20C -20C in 1 hr; From -20C, 10C/hr

4

1st Generation ABCDAluminum Mold & Ring1st Generation ABCD

Aluminum Mold & Ring

• Lowering Temp Causes Compressive Strain on ABCD ring.

• Cracking Detection: Sudden Reduction of Compressive Strain

5

ABCD Test: Corrected Strain

ABCD Test: Corrected Strain

-200

-150

-100

-50

0

50

-65 -55 -45 -35 -25

Temperature, C

Cor

rect

ed S

trai

n, µ

ε

B6230SBS Linear: -58C

6

2nd Generation ABCDSilicone Mold with Protrusions / Invar Ring

2nd Generation ABCDSilicone Mold with Protrusions / Invar Ring

7

Pearson Correlation (FHWA Modified Binder)

Pearson Correlation (FHWA Modified Binder)

ABCDMP1a

(ABCD) MP1a MP1 S m

ABCD 1

MP1a (ABCD) 0.98 1

MP1a 0.71 0.72 1

MP1 0.83 0.85 0.90 1

S (BBR) 0.87 0.86 0.91 0.92 1

m-value (BBR) 0.69 0.69 0.82 0.92 0.78 1

TSRST 0.91 0.94 0.69 0.86 0.84 0.73

8

Effects of Silicone MoldEffects of Silicone Mold

9

-100

-75

-50

-25

0

-40 -30 -20 -10 0

Temp, C

Mic

rost

rain

Al MoldSilicone Mold (1)Silicone Mold (2)-34.0

-33.3

-33.2

ODOT 02CP (70-22)

10

Sample Temperature:Temperature Variation in Chamber

Sample Temperature:Temperature Variation in Chamber

1 2 3

4 5

Temperature

Sensor

Air Blows 4”over samples

Environmental Chamber

Left Middle Right

Cracking Temp: PG 70-28

Loc(#of test)

Left(21)

Middle(13)

Right(11)

Avg -45.3 -45.2 -43.8Std Dev 1.52 1.87 1.53

Cracking Temp: PG 58-28Loc

(#of test)Left(15)

Middle(14)

Right(8)

Avg -36.5 -36.7 -35.5Std Dev 1.00 1.00 1.02

11

12

Biaxial Strain Gauge

Surface Mount RTD

Spot Welded Connector Bracket

13

14

-200

-150

-100

-50

0

50

-60 -50 -40 -30 -20 -10 0

Temp, C

Mic

rost

rain

Lube - Turn (1)Lube - Turn (2)No Lube - No Turn (1)No Lube - No Turn (2)Lube - No Turn

Unaged AAB-1 (PG 58-22)

LubricationLubrication

15

-300

-250

-200

-150

-100

-50

0

50

-60 -50 -40 -30 -20 -10 0

Temp, C

Mic

rost

rain

Lube/TurnLube/TurnNoLube/NoTurnNoLube/NoTurnLube/NoTurn

Unaged AAC-1 (PG 58-16)

The first crack did not occur at the hole.

16

-80

-60

-40

-20

0

20

-50 -40 -30 -20 -10 0

Temp, C

Mic

rost

rain

Unaged AAB-1 (PG 58-22)

Cracked at-36.0-36.1-36.4-36.6All Lube/Turn

Unaged AAF-1

17

RepeatabilityRepeatability

Cracking Temperature Strain

AAA-1 (1) -47.7 -AAA-1 (2) -46.1 55.5AAB-1 (1) -43.0 27.0AAB-1 (2) -43.2 33.9AAC-1 (1) -40.2 29.3AAC-1 (2) -39.8 32.8AAF-1 (1) -36.0 28.2AAF-1 (2) -36.1 28.1AAF-1 (3) -36.4 35.7AAF-1 (4) -36.6 37.5

18

Validation with Pennsylvania Test RoadValidation with Pennsylvania Test Road

• Constructed in 1976 using 6 AC-20 binders

• Sections T1 & T5 cracked 4 month later

– Air Temperature = -29C

– Pavement Temperature = -23C

• Sections T2, T4, T6 cracked after 4 years

• Section T3 never cracked for 7 years

• Overlaid 1984

19

ABCD Results: PA RTFO ResidueABCD Results: PA RTFO Residue

RTFO (1st Try) RTFO (2nd Try)1 2 Avg 1 2 3 Avg

T1 -21.8 Broken -21.8 -21.3 -22.2 - -21.8T2 -34.7 -34.6 -34.7 -34.0 -34.1 -34.4 -34.2T3 -33.2 - -33.2 - - - -T4 -31.1 -32.9 -32.0 -32.0 -32.5 - -32.3T5 -23.2 -26.8 -25.0 -26.0 -25.6 - -25.8T6 -33.1 -34.8 -34.0 -33.6 -33.5 - -33.6

20

ABCD Results: PA PAV ResidueABCD Results: PA PAV Residue

PAV1 2 Avg

T1 -23.1 -21.71 -22.4T2 -28.21 -31.1 -29.7T3 -30.7 -30.72 -30.7T4 -28.5 -29.8 -29.2T5 -25.2 -24.4 -24.8T6 -32.9 -31.6 -32.3

1. Trimming error2. Eccentricity: Ring was off-centered by about 1 mm.

21

Excessive Trimming

22

ABCD (RTFO) VS ABCD (PAV)ABCD (RTFO) VS ABCD (PAV)

-35

-30

-25

-20

-35 -30 -25 -20

ABCD (RTFO)

AB

CD

(RTF

O/P

AV

)

Bad binders: PAV did not change LT performanceGood Binders: PAV lowered LT performance level.

T2

T6T3

T4

T5 T1

23

TSRST VS ABCD (PAV)TSRST VS ABCD (PAV)

y = 0.54x - 10.29R2 = 0.83

y = 0.74x - 2.16R2 = 0.85

-35

-30

-25

-20

-15

-45 -40 -35 -30 -25 -20

ABCD (PAV)

TSR

ST,

C

FHWA StudyPA Study

24

Cracking Index (4yr) vs ABCD (PAV)Cracking Index (4yr) vs ABCD (PAV)

y = 9.75x + 305.20R2 = 0.94

0

20

40

60

80

100

-35 -30 -25 -20

ABCD (PAV), Tcr, C

Cra

ckin

g In

dex

(4yr

)

T6

T3 T2T4

T5

T1

25

Cracking Index (4yr) vs ABCD (RTFO)Cracking Index (4yr) vs ABCD (RTFO)

y = 7.16x + 246.28R2 = 0.98

0

20

40

60

80

100

-35 -30 -25 -20

ABCD Tcr (RTFO), C

Cra

ckin

g In

dex

(4yr

)

26

Cracking Index (7yr) vs ABCD (RTFO)Cracking Index (7yr) vs ABCD (RTFO)

y = 6.26x + 225.60R2 = 0.90

0

20

40

60

80

100

-35 -30 -25 -20

ABCD Tcr (RTFO), C

Cra

ckin

g In

dex

(7yr

)

27

Cracking Index (7yr) vs ABCD (PAV)Cracking Index (7yr) vs ABCD (PAV)

y = 8.91x + 288.02R2 = 0.94

0

20

40

60

80

100

-35 -30 -25 -20

ABCD (PAV) Tcr, C

Cra

ckin

g In

dex

(7yr

)

T6

T3

T2T4

T5

T1

28

Cracking Index (7yr) vs BBR (PAV)Cracking Index (7yr) vs BBR (PAV)

y = 4.93x + 148.09R2 = 0.35

0

20

40

60

80

100

-30 -25 -20 -15

BBR (PAV) Tcr, C

Cra

ckin

g In

dex

(7yr

)

29

Cracking Index (7yr) vs BBR (PAV)Cracking Index (7yr) vs BBR (PAV)

y = 4.20x + 125.14R2 = 0.21

0

20

40

60

80

100

-30 -25 -20 -15

BBR (PAV) Tcr, C

Cra

ckin

g In

dex

(4yr

)

30

Cracking Index (7yr) vs BBR Stiffness (PAV)Cracking Index (7yr) vs BBR Stiffness (PAV)

y = 7.14x + 224.07R2 = 0.77

0

20

40

60

80

100

-35 -30 -25 -20 -15

BBR Stiffness (PAV) Tcr, C

Cra

ckin

g In

dex

(7yr

)

31

Binder (Aggregate) SamplesBinder (Aggregate) Samples

• Canadian Test Roads

• WRI Test Roads

• Penn Test Roads

• FHWA Polymer Modified Asphalts

• SHRP Core Asphalts

• Ohio DOT 36 New Projects

• Thermal Expansion Coefficients of Aggregates

32

SummarySummary

• Sturdy ABCD ring• Improved repeatability (RTD): ~0.5C or less for

binders tested.• ABCD test is forgiving• Good correlation between ABCD and Pennsylvania

Test Road performance• Do we need m-value?• Physical hardening. Is it an issue?

33

Thank You!Thank You!