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  • Effect of Mixture Design on Densification

    Louay Mohammad

    Louisiana Asphalt Technology ConferenceFebruary 23-24, 2005

    Shreveport, Louisiana

  • 2

    Outline

    - Background

    - Objective

    - Scope

    - Mixtures Evaluation

    - Results

    - Concluding Remarks

  • 3

    Objectives of Mix DesignObjectives of Mix Design

    Resist permanent deformation. fatigue cracking repeated load low temperature cracking moisture induced damage

    Resist skid Workability

  • 4

    Steps Involved in the Mixture Design

    1. Materials Selection1. Materials Selection 2. Design Aggregate Structure2. Design Aggregate Structure

    3. Design Binder Content3. Design Binder Content 4. Moisture Sensitivity4. Moisture Sensitivity

    TSRTSR

  • 5

    Superpave Mixture DesignConcerns: Minimum VMA Criteria Difficulties Differentiate sound from

    unsound mixtures higher VMA mixtures

    Cannot guarantee Durable rut resistant

    airairasphaltasphalt

    aggagg

    VOLVOL MASSMASS

    VVTT

    VMAVMA VVEACEAC

    VVVV

  • 6

    Superpave Mixture DesignConcerns: Aggregate Properties/Gradation

    selection 95 percent Aggregate Specification

    Consensus ETG Little research Aggregate Structure/Mixture Design

    and Performance

  • 7

    Superpave Mixture DesignImprovement: Design Aggregate Structure

    Mixture stability Rational approach to design aggregate

    structure based on principles of aggregate packing

    concepts

  • 8

    Objective

    Critically examine Superpave mixture design criterion

    Effect of NMS Aggregate Gradation and type

  • 9

    Scope Aggregate Types

    Two ` Sandstone, Limestone

    Aggregate Structure 12.5 mm NMS 25 mm NMS

    Aggregate gradation Coarse, Medium, Fine Bailey Method

    analytical method that enables blending aggregates using engineering principles and packing theory concepts

  • 10

    Scope Compaction Level

    125 gyrations Binder Type

    PG 76 22M

  • 11

    Methodology Superpave Gyratory Compactor

    Densification Indices, Slope Locking Point

    Pressure Distribution Analyzer Frictional Indices, Locking

    Loaded Wheel Tester PMW

  • K J I H G F E K J I H G F E D C B A D C B A

    Sieve Size (mm) Raised to 0.45 PowerSieve Size (mm) Raised to 0.45 Power

    100100

    00

    % P

    assi

    ng%

    Pas

    sing

    Combined Blend GradationCombined Blend Gradation

    5050

    2020

    8080

    Sieve % PassingA 100B 97C 76D 63E 39F 25G 17H 11I 7J 5K 4.2

    1010

    3030

    4040

    6060

    7070

    9090

    CoarseFine

    1

    2

    34

  • K J I H G F E K J I H G F E D C B A D C B A

    Sieve Size (mm) Raised to 0.45 PowerSieve Size (mm) Raised to 0.45 Power

    100100

    00

    % P

    assi

    ng%

    Pas

    sing

    Combined Blend GradationCombined Blend Gradation

    5050

    2020

    8080

    Sieve % PassingA 100B 98C 85D 72E 58F 40G 32H 21I 12J 7K 4.4

    1010

    3030

    4040

    6060

    7070

    9090

    1

    2

    3

    4

    CoarseFine

  • 14

    Aggregate Gradation SS3/4"

    1/2"

    3/8"

    No. 4

    No. 8

    No. 16

    No. 30

    No. 50

    No. 100

    No. 200

    Sieve Size

    0

    10

    20

    30

    40

    50

    60

    70

    80

    90

    100

    Perc

    ent P

    assing

  • 15

    Aggregate Gradation 1 LS1.5"

    1"3/4"

    1/2"

    3/8"

    No. 4

    No. 8

    No. 16

    No. 30

    No. 50

    No. 100

    No. 200

    Sieve Size

    0

    10

    20

    30

    40

    50

    60

    70

    80

    90

    100

    Per

    cent

    Pas

    sing

  • Mixture Design

    11.19.6 10

    12

    11.1 11.3

    9.1

    1413.1

    8.4 8.5

    14

    02468

    1012141618

    1 LS 0.5 LS 0.5 SS

    Coarse Medium Fine Specs63.5

    58.2 60.564.8 62.7

    58.5

    69

    50 54

    0

    20

    40

    60

    80

    VFA

    1 LS 0.5 LS 0.5 SS

    Coarse Medium Fine

    3.8

    3.0 3.3

    5.1

    4.0

    3.5

    5.1

    3.6

    3.9

    0.0

    2.0

    4.0

    6.0

    %A

    C

    1 LS 0.5 LS 0.5 SS

    Coarse Medium Fine8 5 . 78 9 .3 8 9 .5 89

    8 5 . 1 8 6 . 28 8 89 8 6 . 6 8 6 .4 8 8 89

    0

    20

    40

    60

    80

    100

    %G

    mm

    , Ni

    1 LS 0.5 LS 0.5 SS

  • 1775

    80

    85

    90

    95

    100

    0 30 60 90 120 150 180 210

    No. Of Gyration

    Ht,

    mm

    SGC

    Pressure Distribution Analyzer

    12

    17

    22

    0 100 200 300No. of Gyrations

    FR, p

    siCoarseMediumFine

  • 18

    Superpave Gyratory CompactorLocking Point Number of gyration

    Ht specimen remains constant for three consecutive gyrations

    115.4

    77

    115.4115.4115.5115.5115.6115.6115.7115.7Height, mm

    7675747372717069N0. Gyrations

    75

    80

    85

    90

    95

    100

    0 30 60 90 120 150 180 210

    No. Of Gyration

    Ht,

    mm

  • 19

    115.4

    77

    115.4115.4115.5115.5115.6115.6115.7115.7Height, mm

    7675747372717069N0. Gyrations

    Locking Point

    Superpave Gyratory CompactorLocking Point

  • 20

    80828486889092949698

    0.1 1 10 100 1000

    No. of Gyrations

    % G

    mm

    % @ % @( ) ( )

    Gmm Ndes Gmm NiniLog Ndes Log Nini

    Superpave Gyratory CompactorSlope

  • 21

    75

    80

    85

    90

    95

    100

    0 50 100 150 200

    No. of Gyrations

    % G

    mm

    92%

    N=1

    CDI

    Compaction Densification Index

    N=205

    TDI

    Traffic Densification Index

    Superpave Gyratory CompactorCompaction Indices

  • 22

    Pressure Distribution Analyzer

    Measures the frictional resistance of mixtures during compaction

    Double plate assembly with 3 load cells equally spaced on the perimeter

  • 23100

    300

    500

    700

    900

    1100

    0 50 100 150 200 250 300

    LC1 LC2 LC3

    Pressure Distribution Analyzer

  • 24

    12

    17

    22

    0 100 200 300No. of Gyrations

    FR, p

    si

    CoarseMediumFine

    Pressure Distribution AnalyzerFrictional Resistance

  • 25

    Rate of Change of Frictional Resistance

    -0.10

    0.10.20.30.40.50.6

    0 50 100 150 200 250 300

    No. of Gyrations

    Rate o

    f Chan

    ge of F

    R

    -Maximum interlock in the aggregate structure

    Number of gyrations corresponding to the point of minimum rate of change in FR

    FR Locking Point

    - 510

    15

    20

    25

    0 100 200 300No. of Gyrations

    FR, p

    si

    Coarse Medium Fine

    Pressure Distribution AnalyzerLocking Point

  • 26

    0

    5

    10

    15

    20

    25

    0 50 100 150 200 250 300

    No of Gyrations

    Fric

    tiona

    l Res

    ista

    nce,

    psi

    N=1 N@FR Locking Point

    Compaction Force Index

    200 gyrations

    Traffic Force Index

    Pressure Distribution AnalyzerIndices

  • 27

    Loaded Wheel Tracking Test

  • 28

    Four parameters (indices) are measured from the data collected in the HWT test- Post Compaction Consolidation - Inverse Creep Slope

    - Stripping Inflection Point

    - Stripping Slope

    Loaded Wheel Tracking Test

  • 29

    020406080

    100120140

    1/2"LS C1/2"LS M1/2"LS F1/2" SST C1/2" SST M1/2" SST F1"LS C1" LS M1" LS FSpec

    Superpave Gyratory CompactorLocking Point

  • 30

    0102030405060708090

    100

    % o

    f Nde

    s

    1/2"LS C1/2"LS M1/2"LS F1/2" SST C1/2" SST M1/2" SST F1"LS C

    1" LS M

    1" LS F

    Superpave Gyratory CompactorLocking Point

  • 31

    0123456789

    10

    1/2"LS C1/2"LS M1/2"LS

    1/2" SST C1/2" SST M1/2" SST 1"LS C

    1" LS M

    1" LS F

    Superpave Gyratory CompactorCompaction Slope

  • 32

    050

    100150200250300350400

    1/2"LS C1/2"LS M1/2"LS F1/2" SST C1/2" SST M1/2" SST F1"LS C1" LS M1" LS F

    Superpave Gyratory CompactorCompaction Indices -- CDI

  • 33

    0100200300400500600700800

    1/2"LS C1/2"LS M1/2"LS F1/2" SST C1/2" SST M1/2" SST F1"LS C1" LS M1" LS F

    Superpave Gyratory CompactorCompaction Indices -- TDI

  • 34

    020406080

    100120140

    1/2"LS C1/2"LS M1/2"LS F1/2" SST C1/2" SST M1/2" SST F1"LS C1" LS M1" LS F

    Ndes=125

    Pressure Distribution AnalyzerFR Locking Point

  • 35

    68.860

    52.8

    67.2 62.456.8

    68.8

    46.4 46.4

    0

    20

    40

    60

    80

    100%

    of N

    des

    1/2"LS C1/2"LS M1/2"LS F1/2" SST C1/2" SST M1/2" SST F1"LS C1" LS M1" LS F

    Pressure Distribution AnalyzerFR Locking Point

  • 36

    Frictional Resistance Locking Point

    0

    5

    10

    15

    20

    FR, p

    si

    1/2"LS C1/2"LS M1/2"LS F1/2" SST C1/2" SST M1/2" SST F1"LS C1" LS M1" LS FUSB190 BC

  • 37

    0

    400

    800

    1200

    1600

    2000

    1/2"LS C1/2"LS M1/2"LS F1/2" SST C1/2" SST M1/2" SST F1"LS C1" LS M1" LS F

    Pressure Distribution AnalyzerFR -- CFI

  • 38

    0

    1000

    2000

    3000

    4000

    5000

    1/2"LS C

    1/2"LS M

    1/2"LS F

    1/2" SST C

    1/2" SST M

    1/2" SST F

    1"LS C

    1" LS M

    1" LS F

    Pressure Distribution AnalyzerFR -- DFI

  • 39

    Relationship: No. of Gyrations SGC LP vs. PDA LP

    y = 1.0x - 4.0R2 = 0.95

    40

    50

    60

    70

    80

    90

    100

    40 50 60 70 80 90 100

    SGC Locking Point

    FR L

    ocki

    ng P

    oint

  • 40

    y = 0.70x + 1.65R2 = 0.71

    4.6

    4.8

    5

    5.2

    5.4

    5.6

    4.6 4.8 5 5.2 5.4 5.6

    VTM at SGC Locking Point, %

    VT

    M a

    t FR

    Loc

    king

    Poi

    nt, %

    Relationship: VTM SGC LP vs. PDA LP

  • 41

    0

    100

    200

    300

    400

    4 6 8 10 12 14

    VMA

    CD

    I

    0

    200

    400

    600

    800

    4 6 8 10 12 14

    VMA

    TD

    I

    Relationship: VMA vs SGC CDI & TDI

    Trends Increase VMA

    Higher CDI Lower TDI

    Is there a Min. VMA?

  • 42

    R2 = 0.91

    600

    800

    1000

    1200

    1400

    1600

    1800

    0 100 200 300 400

    CDI

    CFI

    Relationship: Compaction IndicesSGC CDI vs PDA CFI

  • 43

    R2 = 0.19

    2500

    3500

    4500

    400 600 800

    TDI

    TFI

    Relationship: Compaction IndicesSGC TDI vs PDA TFI

  • 44

    R2 = 0.90

    800

    1000

    1200

    1400

    1600

    1800

    4 6 8 10 12

    Compaction Slope

    CFI

    Relationship: SCG Compaction Slope vs. CFI

  • 45

    LWT Test Results

    0

    1

    2

    3

    4

    5

    1/2"LS C1/2"LS M1/2"LS F1/2" SST C1/2" SST M1/2" SST F1"LS C1" LS M1" LS F

  • 46

    012345

    0 100 200 300 400

    CDI

    HWT

    Rut, m

    m

    012345

    1000 1100 1200 1300 1400 1500 1600 1700 1800

    CFI

    HW

    T R

    ut, m

    m

    Relationship: Rut Dept vs. CDI & CFI

  • 47

    012345

    400 500 600 700 800

    TDI

    HWT R

    ut, m

    m

    012345

    3600 3700 3800 3900 4000 4100 4200 4300 4400 4500 4600 4700

    TFI

    HWT

    Rut,

    mm

    Relationship: Rut Dept vs. TDI & TFI

  • 48

    Relationship: Rut Depth vs. FR

    00.5

    11.5

    22.5

    33.5

    44.5

    5

    20 20.5 21 21.5 22 22.5 23

    FR at Locking Point, psi

    HW

    T R

    ut D

    epth

    , mm

  • 49

    R2 = 0.73

    00.5

    11.5

    22.5

    33.5

    44.5

    5

    2 4 6 8 10 12

    Compaction Slope

    HW

    T R

    ut, m

    m

    Relationship: LWT Rut Depth & Compaction Slope

  • 50

    Conclusions- SGC densification curves can provide valuable information

    about mixtures behavior during compaction- CDI, Slope

    Coarse-grades mixtures had higher SGC LP 50% - 70% of Ndesign

    Coarse-grades mixtures had higher Compaction Slope: 6-10

    SGC CDI and PDA CFI indices were higher for Coarse-grades mixtures

    PDA measured LP showed similar ranking as SGC LP Lower

    FR increased with an increased in the NMS

  • 51

    Conclusions

    Good correlation was observed B/W SGC LP and PDA LP SGC CDI and PDA CFI SGC Slope and CDI SGC Slope and LWT rut depth

    Poor correlation was observed B/W SGC TDI and PDA TFI

    Mixtures evaluated performed well in the LWT

  • 52

    Thank You