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Asphalt Mixture Performance Tests
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Outline
Test Background
Sample Preparation
Equipment and Operation
Test Procedure
Data Analysis
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What are “Performance Tests“?
Additional tests beyond volumetric properties that are intended to indicate a mix's resistance to particular distresses (i.e. field performance)
The tests may or may not yield an engineering property that can be used in pavement design or analysis.
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Uses of Performance Tests
For research purposes
To evaluate new materials or design strategies
As part of mix design process (i.e. Balanced Mix Design)
To identify mixtures prone to performance problems
To gain confidence on warranty projects
For Quality Assurance purposes
To assess how plant mix could impact performance and used in pay adjustment factors
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Moisture Damage Susceptibility Tests
Tensile Strength Ratio
AASHTO T 283
Hamburg Wheel Tracker
AASHTO T 324
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Current Use of Moisture Damage Tests
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Moisture Damage Susceptibility Tests
AASHTO T 283
Tensile Strength Ratio
Procedure is well established for mix design approval and verification of plant mix
1 week to complete the test
Precision statistics Single‐operator d2s = 0.093
Multi‐lab d2s = 0.247
Pass/Fail criteria based on TSR
Some states also have minimum conditioned tensile strength
AASHTO T 324
Hamburg Wheel Tracking Test
Specified by a growing number of states and used by numerous researchers
1 to 2 days to complete test
$60,000+ equipment cost
Precision statistics unknown, suspected to be poor
Pass/Fail criteria based on Stripping Inflection Point
Also provides an indication of rutting resistance
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Rutting Tests
E* and Fn
AASHTO TP 79
APA
AASHTO T 340
Hamburg
AASHTO T 324
Shear Stiffness
AASHTO T 320
iRLPD
AASHTO TP 116
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Current Use of Rutting Tests
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Asphalt Pavement Analyzer ‐ APA
0.00
0.50
1.00
1.50
2.00
2.50
0 2000 4000 6000 8000 10000
Loading Cycles
Ru
t D
epth
(m
m)
64-22 70-22 SBS 76-22 Airblown 76-22
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Hamburg Wheel Tracking Test
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Flow Number (Fn)
AASHTO TP 79
Specimens fabricated using SGC
100 mm diameter by 150 mm tall
Air voids 7 ±0.5%
600 kPa axial load
0.1 sec load period, 0.9 sec. rest period
LTPPBind 50% reliability 7‐day max. pavement temp. @ 20 mm depth
10,000 cycles or 5% strain
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Flow Number (Fn) The point in the permanent strain curve where the rate of accumulation of permanent strain reaches a minimum value is defined as the flow number.
A higher flow number indicates better rutting resistance.
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Incremental Repeated Load Permanent Deformation Test
Conduct test on tall specimens compacted in SGC (no coring or cutting).
LTPPBind high temperature, 50% reliability
3 replicates; each specimen is tested incrementally at four stress levels (100, 400, 600, & 800 kPa).
Min. Strain Rate (MSR) at the end of each increment is the measure of permanent deformation resistance.
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Rutting Tests
Flow Number
AASHTO TP 79
APA
AASHTO T 340
Hamburg
AASHTO T 324
Shear Stiffness
AASHTO T 320
iRLPD
AASHTO TP 116
Traffic, Million ESALs
Min. Flow No. APAmax. rut
depth (mm)3
SST Max. Perm. Shear
Strain (%)1
HMA1 WMA2
<3 Not Applicable
3 to <10 53 30 5 3.4
10 to <30 190 105 4 2.1
> 30 740 415 3 0.8
1NCHRP Rpt. 673, 2NCHRP 9‐43, 3OKDOT
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Fatigue Thermal
Modes of Cracking
Top‐Down Reflection Block
Load RelatedEnvironment Related
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Fatigue Tests (repeated load tests)
Bending Beam Fatigue
AASHTO T 321
AMPT Cyclic Fatigue Test
AASHTO TP 107
Texas Overlay Tester
TEX 248‐F; NJDOT B‐10
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Bending Beam Fatigue Test
AASHTO T 321
Beam size – 2.5”x 2”x 15”
7% air voids
Temperature: 20°C
Frequency: 10 Hz
User sets strain magnitude(s)
200 to 800 με is common
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Bending Beam Fatigue
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Bending Beam Fatigue Testing
Long history in research
Used in California on special projects
Specimen fabrication is challenging
Can take several days to complete a single replicate
Poor repeatability
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AMPT Cyclic Fatigue
6 replicates
standard (100 mm dia.×150 mm tall) or small (38 mm dia.×110 mm tall) specimen geometries
AASHTO TP 107
Specimens cored from SGC specimens
Cyclic load: 10 Hz
Test Temp. = [(HTPG+LTPG)/2]‐3
E* needed first to estimate strain levels
Failure defined as a sharp reduction in phase angle
Failure target between 10,000 and 100,000 cycles
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AMPT Cyclic Fatigue Can use results in either a cracking prediction model (for PRS) or as an index parameter.
DR in FlexPAVE Simulation
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AMPT Cyclic Fatigue Can use results in either a cracking prediction model (for PRS) or as an index parameter.
Sapp as Cracking Index Property
12 12
1
1
11
10, 000
C C
RT
app
aD
CS
Sapp > 8 is the preliminary critical value.
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Texas Overlay Tester Tex‐248‐F
Developed to simulate overlay on concrete joint (reflective cracking)
Specimens cut from field cores or SGC specimens; 5 replicates
Epoxied to platens
Repeated saw‐tooth load form; each cycle is 10 seconds; max. opening displacement = 0.025”
Temperature: 25oC
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Texas Overlay Test
Tex-248-F
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Some Top‐Down Cracking Tests
Semi‐Circular BendLADOTD methodASTM D8044
Energy Ratio
OT‐NCAT modified
CantabroAASHTO TP 108
Illinois Flexibility Index Test (I‐FIT); AASHTO TP 124
Texas Overlay TesterTEX 248‐F
IDEAL‐CTASTM D8225
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Semi‐Circular Bend – LA Method
57 mm thick, half‐moon specimens
12 replicates
3 notch depths: 25.4, 31.8, and 38.1 mm
3.0 ± 0.5 mm notch width
25oC
0.5 mm/min load rate
AASHTO R30 long‐term aging
5 days at 85oC
Outlier evaluation
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Semi‐Circular Bend ‐ LA Method• Calculate Strain Energy to
Failure (U) for each sample• Eliminate outliers (ASTM E178)• Correlate Strain Energy (U) and
Notch Depth (a)• Calculate slope
• Calculate J‐integral (Jc)
Louisiana SCB‐Jc CriteriaLevel 1 Traffic: Jc ≥ 0.5Level 2 Traffic: Jc ≥ 0.6
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Illinois Flexibility Index Test (IFIT)
50 mm thick, half‐moon specimens
Notch Depth = 15 mm
Notch Width = 1.5 mm
25oC
50 mm/min load rate 100x faster than SCB‐LA
Minimum of 6 replicates
Test until load < 0.1 kN
Loose‐mix aging
Outlier evaluation
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Illinois Flexibility Index Test (I‐FIT)
𝑮𝒇𝒘𝒇
𝒂𝒍𝒊𝒈 𝑭𝑰
𝑮𝒇
𝒎 𝒙 𝑨
AASHTO T124-16
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Energy Ratio Test
Three IDT tests:
Resilient modulus
Creep compliance
Fracture energy
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Energy Ratio Test
IDT specimens
7±0.5% air voids
3 replicate specimens
Horizontal and vertical strain gauges mounted to both sides of specimens
Servo‐hydraulic test system with environmental chamber
Most commonly conducted at 10oC
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Resilient Modulus
Creep Compliance
Fracture Energy
𝐸𝑅𝐷𝑆𝐶𝐸𝑓 7.294 10 5 𝜎 3.1 6.36 𝑆𝑡 2.46 10 8
𝑚2.98𝐷1
Traffic(ESALs/yr. x 1000)
Minimum Energy Ratio (Roque et al. 2004)
< 250 1
< 500 1.3
< 1000 1.95
Energy Ratio Test
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Overlay Test ‐ NCAT
AMPT fixture
Temperature: 25oC
Specimen cut from SGC specimen
7±0.5% air voids
Repeated direct tension, saw‐tooth waveform; 1 second cycle
Max. displacement = 0.015”
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Overlay Test – NCAT modified
Cycles to failure = peak of Normalized Load ×Cycles graph
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IDEAL‐CT
• 62 ± 1 mm height × 150 ± 2 mm diameter
• Air voids = target ± 0.5%
• target typically 7.0%
• 3 replicates, minimum
• 100 ± 10 N load capacity
• Load Rate 50 ± 2.0 mm/min in LLD Control
• Test duration is typically < 10 seconds
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IDEAL‐CT: Calculation of CTIndex
Failure Energy
Gf
(Joules/m2)
𝐶𝑇𝑡
62𝑙𝐷
𝐺𝑚
10
Pmax
0.75 Pmax
l75
m75
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Low Temperature Cracking Tests
IDT Creep Compliance; AASHTO T 322
Low Temperature Semi‐Circular Bend; AASHTO TP 105
Disk‐Shaped Compact Tension (DCT); ASTM D7313
Thermal Stress Restrained Specimen Test
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Sample Preparation & Test System
TestEquipment Needed for Spec. Prep. Test Machine
Bending Beam Fatigue
Beam compactor & wet saw Servo-hydraulic test system with environmental chamber
AMPT Cyclic Fatigue
SGC, coring rig, wet saw, LVDT-stud alinement jig
AMPT
Texas Overlay Test
SGC, wet saw, & 10 lb. weights
OT machine orAMPT w. OT jig
Semi-CircularBend (LA)
SGC & wet saw Stand-alone servo-hydraulic test system
I-FIT SGC & wet saw Stand-alone servo-hydraulic test system
Energy Ratio SGC, wet saw, stud alinement jig
Servo-hydraulic test system with environmental chamber
IDEAL-CT SGC Stand-alone servo-hydraulic test system
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NCAT suggestions for mix aging
Cracking of asphalt pavement surfaces are strongly influenced by aging of the surface layer.
Top‐down cracking often appears after 3 to 5 years.
A high aging gradient occurs in asphalt pavements. Surface layers age to much greater degree than lower layers.
Aging rate is influenced by climate as quantified by Cumulative Degree Days (CDD).
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NCAT suggestions for mix aging
Several studies have shown that AASHTO R30 long term aging protocol (compacted specimens 5 days at 85C) is not severe enough for surface layers.
Recent NCHRP 9‐54 study recommends loose mix aging at 95C for a period based on climate and pavement layer depth. For most of US, surface layer mixes would be aged for 3 to 5 days.
Limited NCAT aging study found loose mix aging at higher temperature for time based on climate CDD (e.g. 8 hrs at 135C equal to 4‐5 years in Alabama; 6 hrs at 135C equal to 4‐5 years in Minnesota).
NCAT refers to this protocol as “critical” aging.
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Questions
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