Asphalt 101 – Materials: HMA Part 1 Rocky Mountain Asphalt ...Rocky Mountain Asphalt Conference...
Transcript of Asphalt 101 – Materials: HMA Part 1 Rocky Mountain Asphalt ...Rocky Mountain Asphalt Conference...
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Asphalt 101 – Materials: HMA Part 1
Rocky Mountain Asphalt Conference and Equipment Show
February 24, 2011
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SPECIFYING PERFORMANCE
Based on Climate
PG 58 - 28
Performance Grade
Rolling average 7-day max pavement temperature, C
Min pavement temperature, C
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To characterize (test) a PG binder . . .
- 8 individual tests- 6 major pieces of equipment- 3 conditioning steps- ~25 hours total time elapse
PG Binder Tests vs. Temperature
Pavement Temperature, °C- 20 20 60 135
Brookfield
Viscosity(Workability)
DSRHigh
Temperature
(RuttingResistance)
DSRIntermediateTemperature
(FatigueResistance)
BBR & DTT
(Thermal Cracking
Resistance)
Cold Hot
Binder Test Sequence
Unaged Binder
RTFO Aged
PAV Aged
DSRLOH
DSRBBRDTT
FlashRot VisDSR
Binder Condition Test For
SafetyHandlingRutting
RuttingEnvironment / Aging
Fatigue DamageThermal CrackingThermal Cracking
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Aging
Asphalt reacts with oxygen– Becomes harder, more brittle– More Elastic, Less Viscous
Short term– During Mixing with Aggregates (280F-330F)
Long term– In Pavement– Air, Water, Sun
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Asphalt Plant and Construction Aging
Rolling Thin Film Oven (RTFO)
Fan
Rotating Bottle
Carriage
Blowing Air
Binder Test Sequence
Unaged Binder
RTFO Aged
PAV Aged
DSRLOH
DSRBBRDTT
FlashRot VisDSR
Binder Condition Test For
SafetyHandlingRutting
RuttingEnvironment / Aging
Fatigue DamageThermal CrackingThermal Cracking
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Spec Requirement
Binder safe to be heated . . .
– Cleveland Open Cup (COC) Flash Point must be greater than 232oC (450oF).
Binder Test Sequence
Unaged Binder
RTFO Aged
PAV Aged
DSRLOH
DSRBBRDTT
FlashRot VisDSR
Binder Condition Test For
SafetyHandlingRutting
RuttingEnvironment / Aging
Fatigue DamageThermal CrackingThermal Cracking
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Rotational Viscometer (Brookfield)
Inner Cylinder
Torque Motor
Thermosel Environmental
Chamber
Digital Temperature Controller
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Spec Requirement
Make sure binder is not too thick to pump . . .– Keep Viscosity Below 3 Pa-sec at 135oC (275oF)
Binder Test Sequence
Unaged Binder
RTFO Aged
PAV Aged
DSRLOH
DSRBBRDTT
FlashRot VisDSR
Binder Condition Test For
SafetyHandlingRutting
Rutting, HardeningEnvironment / Aging
Fatigue DamageThermal CrackingThermal Cracking
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High temperature or,slow loading behavior, Rutting
High Pavement Temperature– Desert climates– Summer temperatures
Sustained loads– Slow moving trucks– Intersections
100°F
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1 cycle
TimeAA
B
C
CA
B
Fixed Lower Plate
Oscillating Upper Plate
A
Now, Measure the Force Required to Rotate the Upper
Plate
And, Measure When Movement Occurs in
the Binder
Asphalt Glued In-Between
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Elastic Viscous
TimeAA
B
C
Strain
Strain Occurs With Stressδ = 0o
Strain Lags Stressδ = 90o
AA
B
C
AA
Stress
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Vis
cous
, G”
Elastic, G’
Complex M
odulus, G*
δ
Complex Modulus is the vector sum of
Elastic and Viscous Components
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Early part of pavement life
Spec Requirement
Mitigate rutting by . . . G*/sin δ on Unaged binder > 1.00 kPa G*/sin δ on RTFO Aged binder > 2.20 kPa
Binder Test Sequence
Unaged Binder
RTFO Aged
PAV Aged
DSRLOH
DSRBBRDTT
FlashRot VisDSR
Binder Condition Test For
SafetyHandlingRutting
RuttingEnvironment / Aging
Fatigue DamageThermal CrackingThermal Cracking
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Spec Requirement
Reduce Fatique Cracking by . . . G*sin δ on RTFO & PAV aged binder < 5000 kPa
Later part of pavement service life
Binder Test Sequence
Unaged Binder
RTFO Aged
PAV Aged
DSRLOH
DSRBBRDTT
FlashRot VisDSR
Binder Condition Test For
SafetyHandlingRutting
RuttingEnvironment / Aging
Fatigue DamageThermal CrackingThermal Cracking
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Low Temperature, or Fast Loading Behavior-aka Cracking
Low Temperature– Cold climates– Winter
Rapid Loads– Fast moving trucks
σ
ε
Cracking Failure
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BBR Measures Stiffness at Low Temperatures using Beam Theory
S(t) =PL3
4 bh3 δ (t)
Creep stiffness at
t = 60 secs100 grams
Clear Span of Beam, 102 mm
Beam Width, 12.5 mm
Beam Thickness, 6.25 mm
Deflection at t = 60 secs
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Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope
8 15 30 60 120 240
Log
Cre
ep
Stif
fnes
s, S
(t)
Log Loading Time, t (sec)
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Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope
8 15 30 60 120 240
Log
Cre
ep
Stif
fnes
s, S
(t)
Log Loading Time, t (sec)
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Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope
8 15 30 60 120 240
Log
Cre
ep
Stif
fnes
s, S
(t)
Log Loading Time, t (sec)
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Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope
8 15 30 60 120 240
Log
Cre
ep
Stif
fnes
s, S
(t)
Log Loading Time, t (sec)
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Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope
8 15 30 60 120 240
Log
Cre
ep
Stif
fnes
s, S
(t)
Log Loading Time, t (sec)
m
Binder Test Sequence
Unaged Binder
RTFO Aged
PAV Aged
DSRLOH
DSRBBRDTT
FlashRot VisDSR
Binder Condition Test For
SafetyHandlingRutting
RuttingEnvironment / Aging
Fatigue DamageThermal CrackingThermal Cracking
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Thermal Cracking
Question: How Much Should the Asphalt Be Able to Stretch before Breaking?
Answer: at least 1% (in Colorado possibly even more)
How: Find the Temperature Where the Asphalt Can Stretch 1% or More
Conventional AC Grades vs. SHRP Performance Grades
(typical comparisons)
AC-5 AC-10 AC-20 AC-40
PG 52-34 PG 58-28 PG 64-22 PG 70-16
Typical (not absolute) for unmodified asphalts only