resumen superpave
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FHWA Condensed Superpave
Asphalt Specifications
Lecture Series
SUPERPAVE
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Aggregates
Usually refers to a soil that has in some way been processed or sorted.
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Aggregate Size Definitions
• Nominal Maximum Aggregate Size
– one size larger than the first sieve to
retain more than 10%
• Maximum Aggregate Size
– one size larger than nominal maximum
size
100
100 90
72
65
48
36
22
15
9
4
100
99 89
72
65
48
36
22
15
9
4
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100
0.075 .3 2.36 4.75 9.5 12.5 19.0
Percent Passing
control point
restr icted zone
max density line
max
size
nom
max
size
Sieve Size (mm) Raised to 0.45 Power
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Superpave Aggregate Gradation
100
0
.075 .3 2.36 12.5 19.0
Percent Passing
Design Aggregate Structure
Sieve Size (mm) Raised to 0.45 Power
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Superpave Mix Size
DesignationsSuperpave Nom Max Size Max Size
Designation (mm) (mm)
37.5 mm 37.5 50
25 mm 25 37.5
19 mm 19 25
12.5 mm 12.5 19
9.5 mm 9.5 12.5
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Gradat ions
* Considerations: - Max. size < 1/2 AC lift thickness
- Larger max size
+ Increases strength
+ Improves skid resistance + Increases volume and surface area of agg
which decreases required AC content
+ Improves rut resistance
+ Increases problem with segregation of particles - Smaller max size
+ Reduces segregation
+ Reduces road noise
+ Decreases tire wear
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Percent Crushed Fragments in
Gravels
• Quarried materials always 100% crushed
• Minimum values depended upon traffic
level and layer (lift)
• Defined as % mass with one or more
fractured faces
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Percent Crushed Fragments in
Gravels
0% Crushed 100% with 2 or MoreCrushed Faces
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Coarse Aggregate Angularity
Criteria
Traffic Depth from SurfaceMillions of ESALs < 100 mm > 100
mm< 0.3
< 1
< 3< 10
< 30
< 100
100
55/--
65/--
75/--85/80
95/90
100/100
100/100
--/--
--/--
50/--60/--
80/75
95/90
100/100
First number denotes % with one or more fractured faces
Second number denotes % with two or more fractured faces
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Asphalt Cements
Background
History of Specifications
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Background
• Asphalt
– Soluble in petroleum products
– Generally a by-product of petroleum distillation process
– Can be naturally occurring
• Tar
– Resistant to petroleum products
– Generally by-productof coke (from coal)
production
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Penetration Testing
• Sewing machine needle
• Specified load, time, temperature
100 g
Initial
Penetration in 0.1 mm
After 5 seconds
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Penetration Specification
• Five Grades
• 40 - 50
• 60 - 70
• 85 - 100
• 120 - 150
• 200 - 300
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Typical Penetration Specifications
Penetration 40 - 50 200 - 300
Flash Point, C 450+ 350+
Ductility, cm 100+ 100+
Solubility, % 99.0+ 99.0+
Retained Pen., % 55+ 37+
Ductility, cm NA 100+
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Viscosity Graded Specifications
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Types of Viscosity Tubes
Asphalt Institute TubeZietfuchs Cross-Arm
Tube
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Table 1 Example
AC 2.5 AC 40
Visc, 60C 250 + 50 4,000 + 800
Visc, 135C 80+ 300+
Penetration 200+ 20+
Visc, 60C <1,250 <20,000
Ductility 100+ 10+
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40
50
60
7085
100
120
150
200300
Penetration Grades
AC 40
AC 20
AC 10
AC 5
AC 2.5
100
50
10
5
V i s c o s i t y ,
6 0 C ( 1
4 0 F )
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Asphalt Cements
New Superpave Performance Graded Specification
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PG Specifications
• Fundamental properties related to
pavement performance
• Environmental factors
• In-service & construction temperatures
• Short and long term aging
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High Temperature Behavior
• High in-service temperature
– Desert climates
– Summer temperatures
• Sustained loads
– Slow moving trucks
– Intersections
Viscous L iquid
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Pavement Behavior
(Warm Temperatures)
• Permanent deformation (rutting)
• Mixture is plastic• Depends on asphalt source, additives, and
aggregate properties
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Permanent Deformation
Function of warm weather and traffic
Courtesy of FHWA
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Low Temperature Behavior
• Low Temperature
– Cold climates
– Winter
• Rapid Loads
– Fast moving trucks
Elastic Solid
s = t E
Hooke’s Law
h i
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Pavement Behavior
(Low Temperatures)
• Thermal cracks
– Stress generated by contraction due to drop in
temperature
– Crack forms when thermal stresses exceed
ability of material to relieve stress through
deformation
• Material is brittle
• Depends on source of asphalt and aggregate
properties
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Thermal Cracking
Courtesy of FHWA
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Superpave Asphalt Binder Specification
The grading system is based on Climate
PG 64 - 22
Performance
Grade
Average 7-day max
pavement temperature
Min pavement
temperature
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Pavement Temperatures are Calculated
• Calculated by Superpave software
• High temperature – 20 mm below the surface of mixture
• Low temperature
– at surface of mixture
Pave temp = f (air temp, depth, latitude)
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Concentric Cylinder
Concentr ic Cyl inder Rheometers
t Rq =Mi
p Ri2 L
g = W R
Ro - Ri
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Dynamic Shear Rheometer (DSR)
• Parallel PlateShear flow varies with
gap height and radius
Non-homogeneous flow
gR =
R Q
h
tR = 2 M
p R3
Sh t T Bi d A i
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Short Term Binder Aging
• Rolling Thin Film Oven
– Simulates aging from hot mixing and construction
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Pressure Aging Vessel
(Long Term Aging)• Simulates aging of an asphalt
binder for 7 to 10 years
• 50 gram sample is aged for 20
hours
• Pressure of 2,070 kPa (300 psi)
• At 90, 100 or 110 C
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Bending Beam Rheometer
Air Bearing
Load Cell
Deflection Transducer
Fluid Bath
Computer
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Direct Tension Test
D Le
D L
Load
Stress = s = P / A
Strainef
sf
S
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Summary
FatigueCrackingRutting
RTFOShort Term AgingNo aging
Construction
[RV][DSR]
Low Temp
Cracking
[BBR]
[DTT]
PAV
Long Term Aging
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Superpave BinderPurchase Specification
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Superpave Asphalt Binder Specification
The grading system is based on Climate
PG 64 - 22
Performance
Grade
Average 7-day max
pavement temperature
Min pavement
temperature
Performance Grades
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PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG 82
(Rotational Viscosity) RV
90 90 100 100 100 (110) 100 (110) 110 (110)
(Flash Point) FP
46 52 58 64 70 76 82
46 52 58 64 70 76 82
(ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 %
(Direct Tension) DT
(Bending Beam Rheometer) BBR Physical Hardening
28
-34 -40 -46 -10 -16 -22 -28 -34 -40 -46 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -10 -16 -22
-28 -34
Avg 7-day Max, oC
1-day Min, oC
(PRESSURE AGING VESSEL) PAV
ORIGINAL
> 1.00 kPa
< 5000 kPa
> 2.20 kPa
S < 300 MPa m > 0.300
Report Value
> 1.00 %
20 Hours, 2.07 MPa
10 7 4 25 22 19 16 13 10 7 25 22 19 16 13 31 28 25 22 19 16 34 31 28 25 22 19 37 34 31 28 25 40 37 34 31
(Dynamic Shear Rheometer) DSR G* sin
( Bending Beam Rheometer) BBR “S” Stiffness & “m”- value
-24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -
18 -24
-24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12
-18 -24
Performance Grades
(Dynamic Shear Rheometer) DSR G*/sin
(Dynamic Shear Rheometer) DSR G*/sin
< 3 Pa.s @ 135 oC
> 230 oC
CEC
How the PG Spec Works
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PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG 82
(Rotational Viscosity) RV
90 90 100 100 100 (110) 100 (110) 110 (110)
(Flash Point) FP
46 52 58 64 70 76 82
46 52 58 64 70 76 82
(ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 %
(Direct Tension) DT
(Bending Beam Rheometer) BBR Physical Hardening
28
-34 -40 -46 -10 -16 -22 -28 -34 -40 -46 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -10 -16 -22
-28 -34
Avg 7-day Max, oC
1-day Min, oC
(PRESSURE AGING VESSEL) PAV
ORIGINAL
< 5000 kPa
> 2.20 kPa
S < 300 MPa m > 0.300
Report Value
> 1.00 %
20 Hours, 2.07 MPa
10 7 4 25 22 19 16 13 10 7 25 22 19 16 13 31 28 25 22 19 16 34 31 28 25 22 19 37 34 31 28 25 40 37 34 31
(Dynamic Shear Rheometer) DSR G* sin
( Bending Beam Rheometer) BBR “S” Stiffness & “m”- value
-24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -
18 -24
-24 -30 -36 0 -6 -12 -18 -24 -30 -36 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12
-18 -24
How the PG Spec Works
(Dynamic Shear Rheometer) DSR G*/sin
(Dynamic Shear Rheometer) DSR G*/sin
< 3 Pa.s @ 135 oC
> 230 oC
CEC
58 64
Test Temperature
Changes
Spec Requirement
Remains Constant
> 1.00 kPa
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PG 58-22
PG 52-28
PG 64-10PG 58-16
> Many agencies haveestablished zones
PG Binder Selection
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Summary of How to Use
PG Specification
• Determine
– 7-day max pavement temperatures
– 1-day minimum pavement temperature
• Use specification tables to select testtemperatures
•Determine asphalt cement propertiesand compare to specification limits
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Asphalt Concrete MixDesign
History
H Mi A h l C
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Hot Mix Asphalt Concrete
(HMA)
Mix Designs• Objective:
– Develop an economical blend of aggregates and
asphalt that meet design requirements• Historical mix design methods
– Marshall
– Hveem
• New
– Superpave gyratory
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Requirements in Common
• Sufficient asphalt to ensure a durable pavement
• Sufficient stability under traffic loads
• Sufficient air voids
– Upper limit to prevent excessive environmental
damage
– Lower limit to allow room for initial densification due
to traffic
• Sufficient workability
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MARSHALL
MIXDESIGN
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Marshall Mix Design
• Developed by Bruce Marshall for theMississippi Highway Department in the late30’s
• WES began to study it in 1943 for WWII
– Evaluated compaction effort
• No. of blows, foot design, etc.
• Decided on 10 lb.. Hammer, 50 blows/side
• 4% voids after traffic
• Initial criteria were established and
upgraded for increased tire pressures andloads
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Marshall Mix Design
• Select and test aggregate• Select and test asphalt cement
– Establish mixing and compaction
temperatures• Develop trial blends
– Heat and mix asphalt cement andaggregates
– Compact specimen (100 mm diameter)
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Marshall Design Criteria
Light Traffic Medium Traffic Heavy Traffic
ESAL < 104 10 4 < ESAL< 10 ESAL > 106
Compaction 35 50 75
Stability N (lb.) 3336 (750) 5338 (1200) 8006 (1800)
Flow, 0.25 mm (0.1 in) 8 to 18 8 to 16 8 to 14
Air Voids, % 3 to 5 3 to 5 3 to 5
Voids in Mineral Agg.(VMA) Varies with aggregate size
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Asphalt Concrete Mix
DesignSuperpave
Superpave Volumetric Mix
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Superpave Volumetric Mix
Design
• Goals – Compaction method which simulates field
– Accommodates large size aggregates
– Measure of compactibility
– Able to use in field labs
– Address durability issues
• Film thickness
• Environmental
C i
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reaction
frame
rotating
base
loadingram
control and data
acquisition panel
mold
height
measurement
tilt bar
Key Components of Gyratory Compactor
Compaction
Compaction
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Compaction• Gyratory compactor
– Axial and shearing action – 150 mm diameter molds
• Aggregate size up to 37.5 mm
• Height measurement during compaction
– Allows densification during compaction to beevaluated
1.25o
Ram pressure
600 kPa
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% Gmm
Log Gyrations
10 100 1000
Nini
Ndes
Nmax
Three Poin ts on SGC Curve
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SGC Critical Point Comparison
%Gmm= Gmb / Gmm
Gmb = Bulk Mix Specific Gravity from compaction
at N cycles
Gmm = Max. Theoretical Specific Gravity
Compare to allowable values at:
NINI : %Gmm < 89%
NDES: %Gmm < 96% NMAX: %Gmm < 98%
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Design Compaction
• Ndes based on
–
average design high airtemp
– traffic level
• Log Nmax = 1.10 Log Ndes
• Log Nini
= 0.45 Log Ndes
% Gmm
Log Gyrations10 100 1000
Nini
Ndes
Nmax
S T i
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Superpave Testing
• Specimen heights
• Mixture volumetrics
– Air voids – Voids in mineral aggregate (VMA)
– Voids filled with asphalt (VFA)
– Mixture density characteristics
• Dust proportion
• Moisture sensitivity
S i i
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Superpave Mix Design
• Determine mix properties at NDesign and compare tocriteria
– Air voids 4% (or 96% Gmm
)
– VMA See table
– VFA See table
– %Gmm at Nini < 89%
– %Gmmat Nmax < 98%
– Dust proportion 0.6 to 1.2
S Mi D i
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