Cracking Group Experiment
2018 NCAT Test Track Conference
Randy West
Deficiencies of Volumetric-Based Mix Design and QA Tests
• Volumetricpropertiesonlyindicatethequantityofeffectivebinder,notthequality.
• VMAishighlydependentonGsb,whichhaspoorprecisionandistimeconsumingtodetermine.
• Effectsofrecycledmaterialsandmodifiersarenotadequatelyassessed.
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A New Era of Mix Design and QA
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Balanced Mix DesignCrackingResistance RuttingResistance
Modes of Cracking
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Fatigue ThermalTop-Down Reflection Block
Load RelatedEnvironment Related
MnROAD + NCAT Partnership
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Workingtogetheronnationalneedresearchprojects1. Validatingcrackingtestsforbalancedmixdesign2. Documentingthelifecyclebenefitsofpavement
preservation
MnROAD + NCAT Partnership
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NCATTestTrackTop-downcracking
MnROADLow-temperaturecracking
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NCAT Cracking Group Test Sections
NCAT CG Test Sections
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CrackingGroupsections• 7200-ft.sections• Eachsectioninstrumented
Surface Layer 1.5”
IntermediateLayer 2.25”
BaseLayer 2.25”
Granularbase 6”
Stifftracksubgrade infinite
HiMAmix
NCAT CG Field Performance
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1Cycle,10MESALs
Section DescriptionRutting(mm)
Δ IRI(in/mi.)
Δ MTD(mm)
Cracking(%oflane)
N1 20%RAP(Control) 1.7 3 0.4 21.5
N2 Controlw/High Density 2.2 7 0.5 6.2
N5 Low AC,LowDensity 1.2 5 0.4 5.0
N8 20%RAP,5%RAS 1.2 13 0.7 16.9
S5 35%RAP,PG58-28 1.5 1 0.5 0
S6 ControlwHiMA 1.4 10 0.6 0
S13 AZ RubberMix 2.8 3 0.1 0
NCAT CG Field Performance
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1Cycle,10MESALs
0%
5%
10%
15%
20%
25%
30%
0 2 4 6 8 10
TotalCracking(%
ofLan
eArea)
ESALs(Millions)
N1ControlN8Control+5%RASN2Control,HighDensityN5Control,LowDensity,LowAC
NCAT CG Field Performance
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N1Control,Core#2
N1Control,Core#1
NCAT CG Field Performance
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N2HighDensity,Core#2
N2HighDensity,Core#1
NCAT CG Field Performance
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N5LowAC,LowDensity,Core#1
N5LowAC,LowDensity,Core#2
NCAT CG Field Performance
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N8Control+5%RAS,Core#1
N8Control+5%RAS,Core#2
NCAT CG Response Analyses
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SubgradePressureMeasurements
NCAT CG Response Analyses
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SubgradePressureNormalizedto68FversusTime
NCAT CG Response Analyses
17BasePressureMeasurements
NCAT CG Response Analyses
18BasePressureNormalizedto68FversusTime
NCAT CG Response Analyses
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BackcalculatedACModulusNormalizedto68FversusTime
NCAT CG Response Analyses
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N1, Control
ACModulusNormalizedto68FbyWheelpathversusTime
N8, Control+5%RAS
Inside Wheelpath Inside WheelpathOutside Wheelpath Outside Wheelpath
Selected Cracking Tests
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SCB-LAEnergyRatio OT-NCATIFIT OT-TX
Alltestswereconductedonbothlabmixandplantmixsamplesthatwereshort-termandcriticallyaged.
IDEAL-CT
ResultsandanalyseswillbepresentedThursdayat8:00AMbyAdamTaylor
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MnROAD Cracking Group Test Sections
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17
23
22
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20
19
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MnROADTestSections
CrackingGroupCells16-23
Asphalt MixturesCELLNO BINDERGRADE ABR% RAS
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64S-22
30-40 Yes17 20-30 Yes18
15-25 No1920 52S-34 25-35 No21
58H-34 15-25 No221
23 64E-342 10-20 No
Allmixesare12.5mmNMASAllmixesareNdes =80andtargetairvoids=4.0%exceptcell19,whichhasNdes =100andtargetairvoids=3.0%1 Cell22limestoneaggregateinmix2 Highlymodifiedasphaltbinder
Cracking Modes and Testing
• Typesofcrackinginvestigated▻ Lowtemperature▻ Top-downorbottom-upfatiguepossible
• PMLCtesting▻ Lowtemp:DCT-MNandIDTCreep▻ Intermediatetemp:IFIT,OT,BBF▻ E*,TSR,Hamburg
• Samplesprovidedtootherresearchstudies