Asphalt Binders Used in Mongolia in the view of Superpave Specification
Bituminous Material ChairSchulich School of Engineering
University of CalgaryCanada
July 2012
Empirical Asphalt Specifications- penetration, softening point, ductilityâŚ
- tests empirical in nature
- results are related to pavement performance through
experience
SuperPave Asphalt Specification- tests measure physical properties that can be related
directly to field performance by engineering principles
- tests are conducted at temperatures that are
encountered by in-service pavements
SuperPave Binder Specification
- the temperatures at which these properties must be
reached vary depending on the climate in which the binder
is expected to be used
- tests asphalt in conditions that simulate the three critical
stages during the binders life
⢠tests performed on the original asphalt:
- transport, storage, handling
⢠tests performed on asphalt after changes during
construction simulated by RTFOT
⢠tests performed after long service life simulated by
PAV
SuperPave Asphalt Binder Test
⢠Rolling Thin Film Oven Test (RTFOT)
Simulates changes in asphalt binder during mix preparation
and pavement construction
SuperPave Asphalt Binder Test
⢠Pressure Aging Vessel (PAV)
Simulates the effects of long term in-service aging of
asphalt
Sample rack and pan
Loaded Pressure aging vessel (PAV)
SuperPave Asphalt Binder Test
⢠Dynamic Shear Rheometer (DSR)
- Asphalt behaviour depends on both loading time and
temperature and this test evaluates both effects
-measures rheological properties
⢠complex shear modulus (G*)
⢠phase angle (δ)
- intermediate to high temperatures
- original binder RTFOT & PAV residues
SuperPave Asphalt Binder Test
⢠Dynamic Shear Rheometer (DSR)
DSR animation
Geometries for DSR (8 and 25 mm)
SuperPave Asphalt Binder Test
⢠Rotational Viscometer
- ensures that the asphalt is fluid
enough to be pumped and
handled at the hot mix facility
- measured on the original
asphalt binder
SuperPave Asphalt Binder Test
⢠Bending Beam Rheometer
- measures low temperature properties of asphalt
- measures deflection (creep) under a constant load and
temperature
- test temperatures are related to a pavement lowest
service temperature
- tests asphalt after PAV (exposed to hot mixing and in-
service aging)
SuperPave Asphalt Binder Test
⢠Direct Tension Tester
- strong relationship between stiffness
of asphalt binders and the amount of
stretching they undergo before breaking
- important that asphalts be capable of
a minimal amount of elongation
- some asphalts exhibit high creep stiffness but can also
stretch farther before breaking
⢠Direct Tension Tester
- these asphalts are allowed
to have high creep stiffness
(300 to 600 MPa) if they can
also display reasonable ductile
behavior at low temperatures
- if creep stiffness < 300 MPa the direct tension test is
not required PAV asphalt binder
- test measures the performance characteristics of
binders as if they had been exposed to hot mixing and
some in-service aging
SuperPave Asphalt Binder Test
Performance Grades M320 Table
ENCI 579 6 17
PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG 82
(Rotational Viscosity) RV
100 (110)90 90 100 100 100 (110) 100 (110) 100 (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 âSâ Stiffness & âmâ- 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
(Dynamic Shear Rheometer) DSR G*/sin
(Dynamic Shear Rheometer) DSR G*/sin
< 3 Pa.s @ 135oC
> 230 oC
CEC
PG Specification AASHTO M320 Table 3
Multiple Stress Creep Recovery (MSCR)
⢠Multiple Stress Creep Recovery Test of an Asphalt
Binder Using a Dynamic Shear Rheometer (MSCR)
â measures the ability of a binder to maintain an elastic
response at two different stress levels while being
subjected to ten cycles of stress and recovery
â percent recovery in the high stress level can be used
to measure elastic properties as non recoverable
creep compliance Jnr
PG Specification AASHTO M320 Table 3
Multiple Stress Creep Recovery (MSCR)
⢠Standard âSâ Grade, in most typical situations, will be for
traffic levels of less than 10 million equivalent single axle
loads (ESALs).
⢠High âHâ Grade, in most situations, will be for traffic
levels of 10 to 30 million ESALs.
⢠Very High âVâ Grade, in most situations, will be for traffic
levels of greater than 30 million ESALs.
Table 1 Table 2 Table 3Sample Id.
Lab Number
Date
Original Binder Properties
Viscosity @ 135°C [Maximum 3000 mPa.s] [mPa.s]
Flash Point [Minimum 230°C] [°C]
Dynamic Shear [G*/sin d] [min 1.0 kPa] [kPa]
Temp [°C]
Pass / Fail Temp [°C]
Properties after RTFOT
RTFOT Mass Loss [%]
Standard Traffic "S" Grade
J nr3.2 , max 4.0 kPa-1
Heavy Traffic "H" Grade
J nr3.2 , max 2.0 kPa-1
Very Heavy Traffic "V" Grade
J nr3.2 , max 1.0 kPa-1
J nrdiff , max 75%
Test temperature, °C
Properties after PAV
PAV Aging Temperature [°C]
"S" Grade
Dynamic Shear [G* sin d] [max 5000 kPa] [kPa]
"H & V" Grades
Dynamic Shear [G* sin d] [max 6000 kPa] [kPa]
Temp [°C]
DSR Pass / Fail Temp [°C]
Creep stif fness [S-max. 300 MPa] @ 60s
m-value [min. 0.300] @ 60 s
Temperature, [°C]
Failure Strain, [Min. 1.0%] [%]
Performance Grade
Superpave PG Grade
True Superpave Grade
True Superpave Grade by MSCR
T
Composition
PGAC Selection Process
Weather Database
PAVEMENT DESIGN TEMPERATURES -> (HT, LT)
Grade Selection Matrix
âENVIRONMENTALâGRADE -> PG HT-LT
Grade Bumping Protocol(HT Only)
âDESIGNâGRADE -> PG HT-LT
Practical Design Considerations
Special Design Considerations
1. Pavement Design Temperatures2. PGAC Environmental Grade3. PGAC âDesignâ Grade
PG HT-LT
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Specify Site
Reliability, HT Reliability, LTDepth (mm)
Select Model
Pavement Temperature Models
Air Temperatures
â˘Availabilityâ˘Storage & Handlingâ˘Cost vs, Reliability
1
2
3
A
B
STEP
STEP
STEP
Considera
tion
Considera
tion
Determining Pavement Design Temperatures
â the hottest seven-day period was identified and the average maximum air temperature (for this seven-day period) was computed and used to define the hot temperature design condition, and
â the one-day minimum air temperature was used to define the cold temperature design condition
⢠Specifying Reliability â Explicitly Considering Risk
â Reliability is defined as the percent probability, in a single year, that the actual temperature (one day low or high temperature) will not exceed the design temperature
Determining Pavement Design Temperatures
⢠Specifying Reliability â Considering Risk
â Level of reliability is a function of the application
⢠Is this a major highway or low volume road?
⢠Is this a runway or taxiway/apron?
⢠What is the implication of a failure?
â Reliability from the high temperature grade can be different for the low temperature grade
â Consider a high level of reliability (99%) on the high temperature
⢠Rutting leading to safety issues i.e. Hydroplaning
Determining Pavement Design Temperatures
⢠Specifying Reliability â Explicitly Considering Risk
â Consider support for a moderate level (90%) for low pavement temperature (overlays)
⢠Failure modes like cracking are a performance cost/ issue and therefore must be set within the context of life cycle cost considerations.
PGAC Calgary, Alberta
â Environmental Grade PG 58-31
⢠PG 64-31
â Slow traffic where the average traffic speed
is between 20 to 70 km/hr
â Design ESALâs over 0.3 million
⢠PG 70-31
â Standing traffic where the average traffic
speed is less than 20 km/hr
â Design ESALâs over 0.3 million
Materials
⢠Five samples of asphalt binders were provided to our
laboratory
⢠No data attached, only designation: asphalt binder 1,
2, 3, 4 & 5
Decision
⢠To test the materials according to Superpave
specification AASHTO M 320 - 09, Table 1 without flash
point (Mongolian laboratories)
⢠Presently added: AASHTO M 320 - 09, Table 3 (MSCR
â multiple stress and creep recovery test), penetration,
and flash point
⢠AASHTO M 320-09 Table 2 probably not necessary:
more for polymer modified asphalt binders, not critical
for most of straight run materials
Caveat
⢠To really judge the quality and potential field
performance of asphalt binder, one needs to have
more information, i.e. the stability of crude oil supply,
chemical/group composition, etc. We have only
SPECIFICATION tests
⢠Three materials contained water (1, 2 & 5). Samples 1
and 2 contained enough water to prevent
determination of flash point. Other results might be
influenced
Discussion of Test Results
The tested materials can be divided into four âgroupsâ:
⢠Group 1, asphalt binder No.2 (our designation #5319)
- flash point could not be tested: contained water
- RTFOT mass loss - 2.45% (might partially be
- water)
- high temperature parameter G*/sin â original vs
after RTFOT (61.7 °C to 70.2 °C)
- because of huge hardening after RTFOT, in the
MSCR test (would be grade PG 70-xx) material
scores as suitable for very high traffic
- low temperature parameter -25 °C (suitable for
warmer climates)
Discussion of Test Results
The tested materials can be divided into four âgroupsâ:
⢠Group 1, asphalt binder No.2 (our designation #5319)
- likely presence of lighter oils: possibly added to
bring the material to the same consistency level
as the other materials
- should be rejected and not used for paving
anywhere
Discussion of Test Results
⢠Group 2, asphalt binder No. 5 (our designation #5322)
- contained small amount of water
- very good conventional asphalt binder
- meets the requirements of Superpave PG 58-28
but with 4 °C reserve on the low service
temperature side
- meets our âsplitâ Superpave grade PG 58-31
- â T 92 °C: excellent
- according to MSCR test the material meets the
requirements for use in standard traffic which is
normal for conventional asphalt binders
Discussion of Test Results
⢠Group 3, asphalt binders No. 1, and 3 (our designation
#5318 & #5320)
- asphalt binder No. 1 contained enough water to
prevent determination of flash point
- good to very good conventional asphalt binders
- meet the requirements of the Superpave
PG 58-28
- both materials have â 89 °C: very good
- according to MSCR test both materials meet the
requirements for use in standard traffic which is
normal for conventional asphalt binders
⢠Discussion of Test Results
⢠Group 4, asphalt binder No. 4 (our designation #5321)
⢠- reasonably good asphalt binder suitable for
intermediate to warmer climates
⢠- meets the requirements for the Superpave grade
⢠PG 58-22
- â T 84 °C: O.K.
- according to MSCR test the material meets the
requirements for use in standard traffic which is
normal for conventional asphalt binders
⢠- would not be accepted in Alberta (Canada)
because expected high level of thermal cracking