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Performance Grade Binder(SuperPAVE)
Contents Courtesy of 1. Roberts et.al 1996 2. Atkins 20033. WSDOT Pavement Guide
เน้ือหาท่ีสําคัญใน SuperPave (2 hrs)
• Problem Statement– Pavement Temperature
– Existing grading system
• Rise of Modified Binder
• Introduction to Superpave
• Basic of Visco-elasticity
• DSR – complex modulus and phase angle
• Performance Grading– Statistical Temperature
– Selecting binder grade
Limitations of asphalt cement standards
1. Tests are empirical and not directly related to HMA pavement performance.
2. Tests are conducted at one standard temperature in spite of different climatic conditions.
3. Entire range of pavement temperatures at project site is not considered.
4. Long term aging of asphalt cement in service is not considered
5. Asphalt cement of the same grading can have different temperature and performance characteristics.
6. Previous tests and specifications are not applicable to modified asphalt binders which are gaining popularity.
Note: previous standards include penetration grading system and viscosity grading system
Modified Asphalt binder
Demands on properties of asphalt binder
• Lower stiffness (or viscosity) at the high temperaturesassociated with construction. This facilitates pumping of the liquid asphalt binder as well as mixing and compaction of HMA.
• Higher stiffness at high service temperatures. This will reduce rutting and shoving.
• Increased adhesion between the asphalt binder and the aggregate in the presence of moisture. This will reducethe likelihood of stripping.
• Lower stiffness and faster relaxation properties at low service temperatures. This will reduce thermal cracking.
FatigueCrackingRutting
RTFOShort Term AgingNo aging
Construction
[RV] [DSR]
Low TempCracking
[BBR]
[DTT][DTT]
PAVLong Term Aging
FatigueCrackingRutting
RTFOShort Term Aging
RTFOShort Term AgingNo aging No aging
Construction
[RV] [DSR]
Low TempCracking
[BBR]
[DTT][DTT]
PAVLong Term Aging
PAVLong Term Aging
Rotational Viscometer -Superpave
The RV high-temperature (135° C) viscosity measurements are meant to simulate binder workability at mixing and laydown temperatures. Since the goal is to ensure the asphalt binder is sufficiently fluid for pumping and mixing, Superpave specifies a maximum RV viscosity. The RV is more suitable than the capillary viscometer (used for kinematic viscosity) for testing modified asphalt binders because some modified asphalt binders (such as those containing crumb rubber particles) can clog the capillary viscometer and cause faulty readings.
Relates to Handling and Pumping in plant
Bending Beam Rheometer –Superpave
subjects a simple asphalt beam to a small (100-g) load over 240 seconds
Output is creep stiffness of asphalt binder which relates to Low temperature cracking
Direct Tension Test -Superpave
loads a small sample of asphalt binder in tension until it breaks. Failure strain is then calculated. Failure strain is related to Low temperature cracking
Rolling Thin-Film Oven Test
RTFO Samples (left - after aging in the RTFO, center - before aging in the RTFO, right - empty sample jar)
Rolling Thin-Film Oven Test
Short-term aging
163C for 85 minutes
Pressure Aging Vessel
Pressure Aging Vessel
Use Sample from RTFO
Long-term aging
Air pressure 300 psi 90-110C for 20 hours
Simulate aging of 7-10 years
RV
DSR
BBR
Original Properties, Rutting, and Fatigue
DSR EquipmentDSR
EquipmentComputer Control
and Data Acquisition
Dynamic Shear Rheometer –Superpave
Relates to Rutting and Fatigue cracking
Dynamic Shear Rheometer (DSR)
• Parallel Plate Shear flow varies with gap height and radius
Non-homogeneous flow
R = R
h
R = 2 M
R3
1 cycle
TimeAA
B
C
CA
B
Fixed Plate
Oscillating Plate
Test operates at 10 rad/secor 1.59 Hz
360o = 2 radians per circle1 rad = 57.3o
Stress
Elastic Viscous
TimeA
A
B
C
Strain
Strain in-phase = 0o
Strain out-of-phase = 90o
Stress
Viscous Modulus, G”
Storage (=elastic) Modulus, G’
Complex Modulus, G*
Complex Modulus is the vector sum of the storage and viscous modulus
Permanent Deformation
Addressed by:
G*/sin on unaged binder > 1.00 kPa
G*/sin on RTFO aged binder > 2.20 kPa
For the early part of the service life
Question: Why a minimum G*/sin to address rutting
Answer: We want a stiff, elastic binder to contribute to mix rutting resistance
How: By increasing G* or decreasing
Permanent Deformation
Fatigue Cracking
• G* (sin ) on RTFO and PAV aged binder
• The parameter addresses the later part of the fatigue life
• Value must be < 5000 kPa
Fatigue Cracking
• Question: Why a maximum G* sin to address fatigue?
Answer: We want a soft elastic binder (to sustain many loads without cracking)
How: By decreasing G* or decreasing
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
10 16 22 28 34 40 10 16 22 28 34 10 16 22 28 34Average 7-day Maximum Pavement Design
Temperature, oCa
Minimum Pavement Design Temperature, oCa -10 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -10 -16 -22 -28 -34
Flash Point Temp, T 48, Minimum (oC)
Viscosity, ASTM D 4402:b
Maximum, 3 Pa*s, Test Temp, oC
Dynamic Shear, TP 5:c
G*/sinf, Minimum, 1.00 kPa
Test Temp @ 10 rad/s, oC
Mass Loss, Maximum, percent
Dynamic Shear, TP 5:
G*/sinf, Minimum, 2.20 kPa
Test Temp @ 10 rad/s, oC
PAV Aging Temperature, oCd
Dynamic Shear, TP 5:
G*sinf, Maximum, 5000 kPa
Test Temp @ 10 rad/s, oC
Physical Hardeninge
Creep Stiffness, TP 1
Determine the critical cracking temperature as described in PP 42
Direct Tension, TP 3
Determine the critical cracking temperature as described in PP 42
ORIGINAL BINDER
230
135
Performance GradePG 70 PG 76 PG 82
1.00
70 76 82
PRESSURE AGING VESSEL RESIDUE (PP 1)
100 (110) 100 (110) 100 (110)
37 34 31 28
0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24
0 -6 -12 -18 -24 -30 0 -6 -12 -18 -24 0 -6 -12 -18 -24
Report
70 76 82
ROLLING THIN FILM OVEN RESIDUE (T 240)
31 2819 37 34 25 4022
< 70 < 76 < 82
34 31 28 25
Performance Grading System for asphalt binder34 40 46 10 16 22 28 34 40 46 16 22 28 34 40 10 16 22 28 34 40
Average 7-day Maximum Pavement Design
Temperature, oCa
Minimum Pavement Design Temperature, oCa -34 -40 -46 -10 -16 -22 -28 -34 -40 -46 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40
Flash Point Temp, T 48, Minimum (oC)
Viscosity, ASTM D 4402:b
Maximum, 3 Pa*s, Test Temp, oC
Dynamic Shear, TP 5:c
G*/sinf, Minimum, 1.00 kPa
Test Temp @ 10 rad/s, oC
Mass Loss, Maximum, percent
Dynamic Shear, TP 5:
G*/sinf, Minimum, 2.20 kPa
Test Temp @ 10 rad/s, oC
PAV Aging Temperature, oCd
Dynamic Shear, TP 5:
G*/sinf, Maximum, 5000 kPa
Test Temp @ 10 rad/s, oC
Physical Hardeninge
Creep Stiffness, TP 1
Determine the critical cracking temperature as described in PP 42
Direct Tension, TP 3
Determine the critical cracking temperature as described in PP 42
Performance Grade
-12 -18 -24 -30-24 -30 0 -6-36 -6 -12 -18
-30
-24 -30 -36 0 -6 -12 -18 -24 -30
-6 -12 -18 -24-18 -24 -30 0-30 -36 -6 -12-6 -12 -18 -24-24 -30 -36 0
22 19 16
Report
13 31 28 2525 22 19 1616 13 10 722 19
90 90
10 7 4 25
100 100
ROLLING THIN FILM OVEN RESIDUE (T 240)
1.00
46 52 58 64
ORIGINAL BINDER
230
135
PRESSURE AGING VESSEL RESIDUE (PP 1)
46 52 58 64
< 46 < 52 < 58 < 64
PG 46 PG 52 PG 58 PG 64
G*sin
Performance Grading System for asphalt binder34 40 46 10 16 22 28 34 40 46 16 22 28 34 40 10 16 22 28 34 40
Average 7-day Maximum Pavement Design
Temperature, oCa
Minimum Pavement Design Temperature, oCa -34 -40 -46 -10 -16 -22 -28 -34 -40 -46 -16 -22 -28 -34 -40 -10 -16 -22 -28 -34 -40
Flash Point Temp, T 48, Minimum (oC)
Viscosity, ASTM D 4402:b
Maximum, 3 Pa*s, Test Temp, oC
Dynamic Shear, TP 5:c
G*/sinf, Minimum, 1.00 kPa
Test Temp @ 10 rad/s, oC
Mass Loss, Maximum, percent
Dynamic Shear, TP 5:
G*/sinf, Minimum, 2.20 kPa
Test Temp @ 10 rad/s, oC
PAV Aging Temperature, oCd
Dynamic Shear, TP 5:
G*/sinf, Maximum, 5000 kPa
Test Temp @ 10 rad/s, oC
Physical Hardeninge
Creep Stiffness, TP 1
Determine the critical cracking temperature as described in PP 42
Direct Tension, TP 3
Determine the critical cracking temperature as described in PP 42
Performance Grade
-12 -18 -24 -30-24 -30 0 -6-36 -6 -12 -18
-30
-24 -30 -36 0 -6 -12 -18 -24 -30
-6 -12 -18 -24-18 -24 -30 0-30 -36 -6 -12-6 -12 -18 -24-24 -30 -36 0
22 19 16
Report
13 31 28 2525 22 19 1616 13 10 722 19
90 90
10 7 4 25
100 100
ROLLING THIN FILM OVEN RESIDUE (T 240)
1.00
46 52 58 64
ORIGINAL BINDER
230
135
PRESSURE AGING VESSEL RESIDUE (PP 1)
46 52 58 64
< 46 < 52 < 58 < 64
PG 46 PG 52 PG 58 PG 64
Spec requirement to control fatigue cracking
Spec requirement to control rutting
Spec requirement remains constant
Test temperature changes
Spec requirement to control low temp. cracking
G*sin
Prediction of PG Grade for different crude oil blends
Selecting PG grade based on record of temperature
Find hottest 7-day period air temp of each year to calculate average max air temp
Find average 1-day coldest temperature
Alternatives:
1.Use mean temp = 50% reliability
2.Use Mean+/- 2sd.=98% reliability
Comparison between Superpave and Conventional Asphalt Specifications
Superpave
• Specify highest and lowest temperatures
• Requires the same properties, but at different temperatures
• Specifies low-temperature properties
• Specifies properties after long-term aging in service
• Specified tests much more expensive to conduct
• Very limited experience with the new tests specified
Conventional
• Does not specify highest and lowest service temperatures
• Requires different properties, but at the same testing temperatures
• Does not specify low-temperature properties
• Does not specify properties after long-term aging
• Less expensive
• Lots of experience with the tests used
Design Adjustment
• Dynamic Shear Rheometer (DSR) test is conducted at a rate of 10 radians per second, which corresponds to a traffic speed of about 90 km/hr
• Pavements subject to significantly slower (or stopped) traffic such as intersections, toll booth lines and bus stops should contain a stiffer asphalt binder than that which would be used for fast-moving traffic.
• Superpave allows the high temperature grade to be increased – by one grade for slow transient loads– by two grades for stationary loads. – Additionally, the high temperature grade should be increased by
one grade for anticipated 20-year loading in excess of 30 million ESALs.
• For pavements with multiple conditions that require grade increases only the largest grade increase should be used.