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The methods used for the characterization and testing of asphalt
materials have advanced considerably in the past 20 years. The
State of Qatar has adopted most of these methods in order to build
long-lasting pavement infrastructure. Qatar Geotechnical and
Environmental Company (QGEC) has acquired and
commissioned both conventional and advanced asphalt materials
tests. The operations of the majority of these tests are computerautomated. QGEC has also developed a quality system for
keeping records and reporting results to its clients. Most
importantly, QGEC has staff members who are highly experienced
in performing the tests, analysis of the results, and preparing
technical reports. QGEC continues to pay great attention to the
training of its staff in order to maintain their skills and continue to
develop their knowledge. Appendix A includes a list of asphalt
tests at QGEC. In the following sections, we present an overview
of some of these tests.
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The rotational viscometer is used to
measure the viscosity of asphalt
binders at various temperatures; see
Figure 1 of rotational viscometer at
QGEC. The results of this test are
used to determine if a binder
viscosity meets the specifications in
the
Performance
Grade
(PG)
Superpave system. Viscosity at high
temperatures is an important
property in order to ensure that the
binder is suitable for pumping and
mixing. In addition, the results are
often used to determine the binder
viscosity and temperatures at which
to perform mixing and compaction
of asphalt mixtures. ASTM D4402
and AASHTO T316 describes the
experimental methods to perform
this test.
Figure 1: Rotational Viscomester Used to Determine Viscosity
at High Temperatures.
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QGEC has the rolling-thin film oven (RTFO) that is used to simulate short-term aging
of asphalt binders. This aging occurs because of the effects of heat and air during the
mixing and compaction of asphalt mixtures. RTFO is used to determine the change of
weight of an asphalt binder because of the loss of volatile materials during the aging
process. Furthermore, binders aged in the RTFO are used for testing in the Dynamic
Shear Rheometer (DSR). The RTFO aging method is described in ASTM D2872 and
AASHTO T240.
The Pressure Aging Vessel (PAV) simulates long-term aging of asphalt binders. This
long-term aging is associated with the brittleness and changes in chemical properties of
asphalt binders after some years in service (7 to 10 years). Binders aged in the PAV are
used for testing in the DSR and Bending Beam Rheometer (BBR). The PAV aging
method is described in ASTM D6521 and AASHTO R28. Figure 2 shows both the
RTFO and PAV devices.
Figure 3: A Picture of the Pressure Aging Vessel (right) and Rolling Thin-Film Oven (left).
The Dynamic Shear Rheometer (DSR) applies
oscillatory loading to determine the
rheological properties (stiffness and phase
angle) of asphalt binders. The results are
used to determine if the binder meets the PG
Superpave specifications for resistance to
rutting (original and RTFO-aged binder) and
fatigue cracking (PAV-aged binder).
In
addition, the DSR in OGEC is capable of
conducting frequency sweep tests and
multiple temperatures. The team at OGEC
uses these results to develop the master
curve for an asphalt binder. The master
curve gives information about the response
of the binder at a range of temperatures and
frequencies. The DSR test is conducted
following the ASTM D7175 and AASHTO
T315 methods.
Figure 4: Dynamic Shear Rheometer Used to Measure Resistance of
Asphalt Binder to Rutting and Fatigue Cracking.
The DSR at QGEC has the testing capabilities and software
to perform the multiple stress creep recovery (MSCR) test
to determine the resistance of the binder to permanent
deformation at relatively high stresses. The team at QGEC is
experienced in the analysis of the MSCR test results (i.e.
analysis of creep compliance). The MSCR test is performed
according to ASTM D7405 and AASHTO TP70.
The team in QGEC has the expertise to analyze the results
from the tests according to the Superpave specifications for
performance-graded asphalt binder (ASTM D6373 or
AASHTO M320). We provide the backup test results and
analysis that support the performance grade of an asphalt
binder. In addition, QGEC provides complete analysis
following the AASHTO MP19, which determines the hightemperature grade of an asphalt binder following the MSCR
test method.
The Bending Beam Rheometer (BBR) is used to evaluate
the low temperature grade as part of the Superpave PG
system. The BBR measures the low temperature properties,
which are used to determine the resistance of the asphalt
binder to cracking. The BBR test is performed according to
ASTM D6648 and AASHTO T313 procedures. Figure 5
shows the BBR at QGEC.
In summary, the tests available at QGEC can be used
collectively to verify or determine the performance grade of
an asphalt binder. They can also be used to investigate the
effect of various modifying techniques on the rheological
properties of asphalt binders.
Figure 5: The Bending Beam Rheomter Used to Measure LowTemperature Properties of Asphalt Binder.
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QGEC is equipped with all the equipment needed for asphalt mixture designs
according to the Marshall and Superpave methods. QGEC has the setups to
determine the bulk specific gravity and maximum specific gravity of mixtures.
In addition, QGEC has the Ignition Oven, which is used to determine the
asphalt content following the AASHTO T308 and ASTM D6307 methods.
Asphalt content is an important property that affects all aspects of
performance of asphalt mixture such as resistance to aging, moisture damage,
rutting and cracking.
QGEC has the Superpave Gyratory Compactor (SGC). This is considered the
backbone of the Superpave mixture design method. It is used for compacting
mixtures in order to determine their density and other volumetrics properties
as part of the mixture design method. In addition, the SGC can be used to
assess the compacatibility of asphalt mixture. It is also an a very good quality
control/quality assurance method to determine the percent air voids or
density of plant-prepared mixtures. Consequently, engineers may use the
results to determine if they are changes in the materials or plant operations
that affect the production of the mixture to meet specifications. The SGC is
used to prepare specimen in order to determine their mechanical properties
using other tests. The SGC compaction is done according to AASHTO T312,
and a picture of SGC is shown in Figure 6. The SGC is calibrated to ensure
that the compaction parameters (internal angle, pressure, and height
measurements) are according to specifications.
The capabilities at QGEC include the Asphalt
Mixture Performance Tester (AMPT); see Figure
7.
This apparatus is equipped with the
mechanisms to perform the dynamic modulus
and flow number tests. The AMPT is equipped
with data acquisition systems and computer
software to perform the test, analyze the data,
and present the results. The dynamic modulus
test results are needed for mechanistic-empirical
design of asphalt pavements. The test is
performed according to AASHTO T342 and
AASHTO TP79. The flow number test applies
repeated loads to determine the resistance of
asphalt mixtures to permanent deformation.
The test is performed following the AASHTO
TP79 procedure. In addition to performing and
analyzing these tests, the QGEC team has the
expertise to develop master curves for asphalt
mixtures by conducing the dynamic modulus at
multiple temperatures and multiple frequencies.
AASHTO PP61 is used to develop the master
curve.
Figure 6: Superpave Gyratory Compactor Used for Preparation of Asphalt
Mixtures.
Figure 7: Asphalt Mixture Performance Tester (AMPT) for Measuring Dynamic Modulus and Flow Number.
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QGEC has invested considerably in the development of the state-ofpractice laboratory with equipment for testing asphalt materials. QGEC
has highly-qualified staff to perform the tests, report the results in
comparison to specifications, and provide detailed reports with analysis
of test data. QGEC welcomes the opportunity to partner with Public
Works Authority, contractors and consultants in order to provide high
quality laboratory testing services. For more information please contact:
Mr. Basim Disi
General Manager
Qatar Geotechnical & Environmental
Telephone: +974 44501473 / 74
Fax: +974 44501537
Cell : +974 66877219
Email: b.disi@qgec.net , main@qgec.net
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P.O Box No: 22054
Doha-Qatar
Web page: www.qgec.net
Description
Method
Penetration of Bituminous Materials
ASTM D5
AASHTO T49
Softening Point of Bitumen (Ring-and-Ball Apparatus)
ASTM D36
AASHTO T53
Density of Semi-Solid Bituminous Materials (Pycnometer Method)
ASTM D70
AASHTO T228
Flash and Fire Points By Cleveland Open Cup Tester
ASTM D92
AASHTO T48
Ductility of Bituminous Materials
ASTM D113
AASHTO T51
Solubility of Asphalt Materials in Trichloroethylene
ASTM D2042
AASHTO T44
Effect of Heat and Air on a Moving Film of Asphalt (Rolling Thin-Film Oven Test)
ASTM D2872
AASHTO T240
Determination of Asphalt Viscosity at Elevated Temperatures Using a Rotational Viscometer
ASTM D4402
AASHTO T316
Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel
ASTM D6521
AASHTO R28
Determining the Flexural Creep Stiffness of Asphalt Binder Using the Bending Beam Rheometer (BBR)
ASTM D6648
AASHTO T313
Determining the Separation Tendency of Polymer from Polymer Modified Asphalt (specimen preparation)
ASTM D7173
Description
Method
Determining the Rheological Properties of Asphalt Binder Using a Dynamic Shear Rheometer (DSR)
ASTM D7175
AASHTO T315
Multiple Stress Creep Recovery (MSCR) Test of Asphalt Binder Using a Dynamic Shear Rheometer (DSR)
ASTM D7405
AASHTO TP70
Specification for Performance-Graded Asphalt Binder (Multiple Tests)
ASTM D6373 AASHTO M320
Specification for Performance-Graded Asphalt Binder Using Multiple Stress Creep Recovery (MSCR) Test (Multiple Tests)
AASHTO MP19
Determining the Asphalt Binder Content of Hot-Mix Asphalt (HMA) by the Ignition Method
ASTM D6307
AASHTO T308
Standard Method of Test for Resistance to Plastic Flow of Asphalt Mixtures Using Marshall Apparatus
AASHTO T245
Standard Method of Test for Preparing and Determining the Density of Hot Mix Asphalt (HMA) Specimens by Means of the
Superpave Gyratory Compactor
AASHTO T312
Asphalt Mixture Performance Tester (AMPT) (Dynamic Modulus and Flow Number)
AASHTO T342 AASHTO
TP79
AASHTO PP61
Description
Method
Emulsified Asphalt Distillation, Water in Bitumen Emulsions
ASTM D244
Distillation of Cutback Asphaltic (Bituminous) Products
ASTM D402
Saybolt Viscosity
ASTM D88
Cohesion of Slurry Seal
ASTM D3910
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BS 598-108:1990
BS EN 12272-1:2002
Rate of Spread of Coated Chippings
Rate of Spread and Accuracy of Spread of Binder and Chippings
Slurry Surfacing Test Methods: Consistency
BS EN 12274-3:2002
Particle Charge of Cationic Emulsified Asphalts
ASTM D244