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

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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 gyratory-compacted specimens.

  • Experimental Plan Materials

    Plant-produced loose mixtures

    Mixture Type NMAS (mm) Asphalt Binder RAP Content (%) RSF9.5A 9.5 PG 64-22 30 RS9.5D 9.5 PG 76-22 20

    SM12.5A 12.5 PG 64-22 30 RI19.0B 19.0 PG 64-22 20

    RI19.0B(2) 19.0 PG 64-22 34 RB25.0B 25.0 PG 64-22 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

    1.0E-08 1.0E-05 1.0E-02 1.0E+01

    |E*|

    (MPa

    )

    Reduced Frequency (Hz)

    RSF9.5A

    1.0E+02

    1.0E+03

    1.0E+04

    1.0E+05

    1.0E-08 1.0E-05 1.0E-02 1.0E+01|E

    *| (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)

    RSF9.5A-Large-1RSF9.5A-Large-2RSF9.5A-Large-3RSF9.5A-Small-1RSF9.5A-Small-2RSF9.5A-Prism-1RSF9.5A-Prism-2

    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

    (1-C

    )

    Nf

    RSF9.5A-LargeRSF9.5A-SmallRSF9.5A-Prism

    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)

    RI19.0B-Large-1RI19.0B-Large-2RI19.0B-Large-3RI19.0B-Small-1RI19.0B-Small-2

    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

    (1-C

    )

    Nf

    RI19.0B-Large

    RI19.0B-Small

  • 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)

    Vertical-1Vertical-2Horizontal-4core-1Horizontal-4core-2Horizontal-4core-3Horizontal-2core-1Horizontal-2core-2

    1E+2

    1E+3

    1E+4

    1E+5

    1E-6 1E-3 1E+0

    |E*|

    (MPa

    )

    Reduced Frequency (Hz)

    100mm-1100mm-2100mm-338mm-Vertical-138mm-Vertical-238mm-Vertical-338mm-Horizontal-138mm-Horizontal-238mm-Horizontal-3

  • Results Effect of Coring Direction

    All of the horizontally-extracted 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 gyratory-compacted samples for each mixture evaluated • Extracted four small specimens from inner 100-mm 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 Specimen-to-Specimen 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

    1E-4 1E-2 1E+0 1E+2 1E+4

    |E*|

    (MPa

    )

    Reduced Frequency (Hz)

    1BL - 3.9%1FL - 3.7%1FR - 3.5%

    05

    10152025303540

    1E-4 1E-2 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

    (1-C

    )

    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 Specimen-to-Specimen Variability – RB25.0B

    1E+2

    1E+3

    1E+4

    1E+5

    1E-4 1E-2 1E+0 1E+2 1E+4

    |E*|

    (MPa

    )

    Reduced Frequncy (Hz)

    3BL - 5.2%3BR - 4.1%3FR - 5.0%

    05

    10152025303540

    1E-4 1E-2 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

    (1-C

    )

    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 gyratory-compacted 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 100-mm diameter of gyratory-compacted 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 180-mm 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 100-mm

    diameter of SGC sample • Extract two specimens per lift from 6-in 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 peak-to-peak on-specimen 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�Specimen-to-Specimen Variability – RS9.5DResults�Specimen-to-Specimen Variability – RB25.0BResults�SummaryProposed Specifications�OverviewProposed Specifications�Key Differences from Large Specimen Specs & QuestionsProposed Specifications�Key Differences from Large Specimen Specs & QuestionsThank you!