Proposed Small Specimen Geometry Specifications · 2017. 6. 16. · Proposed Small Specimen...
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Proposed Small Specimen Geometry Specifications
Specimen Fabrication, AMPT Dynamic Modulus, and AMPT Cyclic Fatigue
Cassie Castorena, Y. Richard Kim, Kangjin Lee,
and Sonja Pape North Carolina State University
Presented to the Asphalt Mixture ETG Ames, IA 5/1/2017

Outline
Introduction Experimental Plan Results Proposed Specifications

Introduction Small Specimen Geometries
Proposed to enable field core testing (Kutay et al. 2009, Park and Kim 2013, Li and Gibson 2013, and Bowers et al. 2015)
130 mm
100 mm
110 mm
38 mm
25 mm
110 mm Thin layer

Improve the efficiency of laboratory specimen fabrication
Introduction Small Specimen Geometries
Fatigue Tests
Large Specimen
E* Tests
Small Specimen
E* Tests Fatigue Tests

Introduction NCHRP IDEA Project Objectives
Evaluate the effects of specimen geometry on dynamic modulus and direct tension fatigue tests using mixtures with various NMAS values.
Optimize the laboratory fabrication of small specimens extracted from gyratorycompacted specimens.

Experimental Plan Materials
Plantproduced loose mixtures
Mixture Type NMAS (mm) Asphalt Binder RAP Content (%) RSF9.5A 9.5 PG 6422 30 RS9.5D 9.5 PG 7622 20
SM12.5A 12.5 PG 6422 30 RI19.0B 19.0 PG 6422 20
RI19.0B(2) 19.0 PG 6422 34 RB25.0B 25.0 PG 6422 30

Experimental Plan Test Methods
Dynamic Modulus
Cyclic Fatigue
Large Specimen Small Specimen Test Temperatures 4, 20, 40, and (54)°C Test Frequencies 25, 10, 5, 1, 0.5, and 0.1 Hz
Large Specimen Small Specimen Test Temperature 18°C
Test Frequency 10 Hz Epoxy Curing Time 16 hours 1 hour

Experimental Efforts Specimen Fabrication
178 mm
150 mm
100 mm
150 mm
110 mm
38 mm
178 mm
150 mm
110 mm
38 mm
140 mm
150 mm

Results Specimen Geometry Effects
1.0E+02
1.0E+03
1.0E+04
1.0E+05
1.0E08 1.0E05 1.0E02 1.0E+01
E*
(MPa
)
Reduced Frequency (Hz)
RSF9.5A
1.0E+02
1.0E+03
1.0E+04
1.0E+05
1.0E08 1.0E05 1.0E02 1.0E+01E
* (M
Pa)
Reduced Frequency (Hz)
RI19.0B
Solid: large specimenLine: small cylindrical specimenEmpty: small prismatic specimen
Blue: 4°C test temperatureGreen: 20°C test temperature
Yellow: 40°C test temperatureRed: 54°C test temperature

Results Specimen Geometry Effects  RSF9.5A
0.0
0.2
0.4
0.6
0.8
1.0
0.0E+00 5.0E+05 1.0E+06 1.5E+06
Pseu
do S
tiffn
ess
(C)
Damage Parameter (S)
RSF9.5ALarge1RSF9.5ALarge2RSF9.5ALarge3RSF9.5ASmall1RSF9.5ASmall2RSF9.5APrism1RSF9.5APrism2
y = 0.4898xR² = 0.9998
0.0E+00
2.0E+04
4.0E+04
6.0E+04
8.0E+04
1.0E+05
0 50,000 100,000 150,000 200,000
Sum
(1C
)
Nf
RSF9.5ALargeRSF9.5ASmallRSF9.5APrism
Damage Characteristic Curves Failure Criterion

0.0
0.2
0.4
0.6
0.8
1.0
0.0E+00 5.0E+05 1.0E+06 1.5E+06
Pseu
do S
tiffn
ess
(C)
Damage Parameter (S)
RI19.0BLarge1RI19.0BLarge2RI19.0BLarge3RI19.0BSmall1RI19.0BSmall2
Results Specimen Geometry Effects  RI19.0B
Damage Characteristic Curves Failure Criterion
y = 0.4424xR² = 0.9992
0.0E+00
5.0E+03
1.0E+04
1.5E+04
2.0E+04
2.5E+04
0 20,000 40,000 60,000
Sum
(1C
)
Nf
RI19.0BLarge
RI19.0BSmall

Results FlexPAVE Pavement Performance Prediction

Results Effect of Coring Direction  RI19.0B
0.00.10.20.30.40.50.60.70.80.91.0
0.0E+0 5.0E+5 1.0E+6 1.5E+6
Pseu
do S
tiffn
ess
(C)
Damage Parameter (S)
Vertical1Vertical2Horizontal4core1Horizontal4core2Horizontal4core3Horizontal2core1Horizontal2core2
1E+2
1E+3
1E+4
1E+5
1E6 1E3 1E+0
E*
(MPa
)
Reduced Frequency (Hz)
100mm1100mm2100mm338mmVertical138mmVertical238mmVertical338mmHorizontal138mmHorizontal238mmHorizontal3

Results Effect of Coring Direction
All of the horizontallyextracted specimens subjected to fatigue testing experienced end failure • Vertical coring preferred!
Middle Failure
End Failure

Results Air Void Variability
Charging the center of the gyratory compaction mold reduces air void variability
Produced three gyratorycompacted samples for each mixture evaluated • Extracted four small specimens from inner 100mm diameter • All of the specimens were tested regardless of air void content
All air void contents within the range of ± 0.7% of the average
0%
5%
10%
15%
20%
25%
30%
35%
40%
PP 60 Center Pour
Perc
enta
ge o
f Spe
cim
ens
Out
side
of ±
0.5%
* Based on ~50 specimens for each
method

Results Statistics on the Middle Failure using Vertical Coring
Fabricated two gyratory specimens for each mixture Extracted four cores from a gyratory specimen Tested all eight specimens for each mixture
Mixture End failures/ Number of Tests
RS9.5D 0/8
SM12.5A 1/8
RI19.0B 2/8
RB25.0B 0/8
Middle Failure
End Failure

Results SpecimentoSpecimen Variability – RS9.5D
0.0
0.2
0.4
0.6
0.8
1.0
0E+0 2E+5 4E+5 6E+5
Pseu
do S
tiffn
ess
(C)
Damage Parameter (S)
2BL  3.9% 2BR  3.9%2FL  4.0% 2FR  3.5%3BL  4.1% 3BR  3.7%3FL  3.5% 3FR  3.6%
1E+2
1E+3
1E+4
1E+5
1E4 1E2 1E+0 1E+2 1E+4
E*
(MPa
)
Reduced Frequency (Hz)
1BL  3.9%1FL  3.7%1FR  3.5%
05
10152025303540
1E4 1E2 1E+0 1E+2 1E+4
Phas
e An
gle
(°)
Reduced Frequency (Hz)
1BL  3.9%1FL  3.7%1FR  3.5%
y = 0.6253xR² = 0.9986
0E+0
2E+3
4E+3
6E+3
8E+3
1E+4
1E+4
1E+4
0E+0 5E+3 1E+4 2E+4 2E+4
Sum
(1C
)
Cycles to Failure (Nf)
2BL  3.9%2BR  3.9%2FL  4.0%2FR  3.5%3BL  4.1%3BR  3.7%3FL  3.5%3FR  3.6%

Results SpecimentoSpecimen Variability – RB25.0B
1E+2
1E+3
1E+4
1E+5
1E4 1E2 1E+0 1E+2 1E+4
E*
(MPa
)
Reduced Frequncy (Hz)
3BL  5.2%3BR  4.1%3FR  5.0%
05
10152025303540
1E4 1E2 1E+0 1E+2 1E+4
Phas
e An
gle
( °)
Reduced Frequncy (Hz)
3BL  5.2%3BR  4.1%3FR  5.0%
0.0
0.2
0.4
0.6
0.8
1.0
0E+0 1E+5 2E+5 3E+5
Pseu
do S
tiffn
ess
(C)
Damage Parameter (S)
1BL  4.0%1BR  4.0%1FL  4.4%1FR  5.3%2BL  4.8%2BR  4.8%2FL  4.9%  void
y = 0.4678xR² = 0.9675
0E+01E+32E+33E+34E+35E+36E+37E+38E+3
0E+0 5E+3 1E+4 2E+4 2E+4
Sum
(1C
)
Cycles to Failure (Nf)
1BL  4.0%1BR  4.0%1FL  4.4%1FR  5.3%2BL  4.8%2BR  4.8%2FL  4.9%

Results Summary
Small specimen testing provides equivalent dynamic modulus test results to large specimen testing at low and intermediate temperatures. • Do not recommend testing at 54°C
Small specimen testing provides equivalent cyclic fatigue test results to large specimen testing
Anisotropy in gyratorycompacted samples does not affect dynamic modulus or cyclic fatigue test results.
Horizontal coring in laboratory specimen fabrication should be avoided because it leads to end failure in cyclic fatigue tests.
The recommended procedure for laboratory fabrication of small specimens is the vertical coring of four specimens from the inner 100mm diameter of gyratorycompacted samples.

Proposed Specifications Overview
Three specifications • Fabrication
Follows AASHTO PP60 Covers laboratory specimen fabrication and
extraction of small specimens from field cores
• AMPT Dynamic Modulus Testing Follows AASHTO TP79
• AMPT Cyclic Fatigue Testing Follows AASHTO TP107

Proposed Specifications Key Differences from Large Specimen Specs &
Questions Fabrication
• Prepare 180mm tall SGC sample Charge the center of the mold in two lifts,
rod each lift Question: Does anyone have suggestions for
facilitating charging the center of the mold? • Extract four specimens from inner 100mm
diameter of SGC sample • Extract two specimens per lift from 6in field core

Proposed Specifications Key Differences from Large Specimen Specs &
Questions AMPT Dynamic Modulus
• Select test temperatures using AASHTO PP61 3 temperatures
• Apply 50 to 75 peaktopeak onspecimen microstrain
AMPT Cyclic Fatigue • 5 min epoxy • Use adapters to attach specimen to AMPT • Apply reduced seating load of 10 N • Question: For fatigue testing, would it be better to
require the testing of three or four specimens? Both
• Increase air void tolerance to ± 0.7%, to be refined upon Ruggedness Testing
• Question: Agree or adopt ± 0.5% from large specimen testing?

Thank you!
Questions?
Proposed Small Specimen Geometry Specifications ��Specimen Fabrication, AMPT Dynamic Modulus, and AMPT Cyclic Fatigue�OutlineIntroduction�Small Specimen GeometriesIntroduction�Small Specimen GeometriesIntroduction�NCHRP IDEA Project ObjectivesExperimental Plan�MaterialsExperimental Plan�Test MethodsExperimental Efforts�Specimen FabricationResults�Specimen Geometry EffectsResults�Specimen Geometry Effects  RSF9.5AResults�Specimen Geometry Effects  RI19.0BResults�FlexPAVE Pavement Performance PredictionResults�Effect of Coring Direction  RI19.0BResults�Effect of Coring DirectionResults�Air Void VariabilityResults�Statistics on the Middle Failure using Vertical CoringResults�SpecimentoSpecimen Variability – RS9.5DResults�SpecimentoSpecimen Variability – RB25.0BResults�SummaryProposed Specifications�OverviewProposed Specifications�Key Differences from Large Specimen Specs & QuestionsProposed Specifications�Key Differences from Large Specimen Specs & QuestionsThank you!