QGEC Asphalt Testing and Analysis Capabilities

Introduction

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 computer-automated. 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.

Asphalt Binder Tests

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.

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 high-temperature 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 Low-

Temperature Properties of Asphalt Binder.

Asphalt Mixture Tests 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.

Summary QGEC has invested considerably in the development of the state-of-practice

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    P.O Box No: 22054 Doha-Qatar

Web page: www.qgec.net

Appendix A: Examples of Asphalt Testing Capabilities at QGEC

Description Method

Penetration of Bituminous Materials ASTM D5AASHTO T49

Softening Point of Bitumen (Ring-and-Ball Apparatus) ASTM D36AASHTO T53

Density of Semi-Solid Bituminous Materials (Pycnometer Method) ASTM D70AASHTO T228

Flash and Fire Points By Cleveland Open Cup Tester ASTM D92AASHTO T48

Ductility of Bituminous Materials ASTM D113AASHTO T51

Solubility of Asphalt Materials in Trichloroethylene ASTM D2042AASHTO T44

Effect of Heat and Air on a Moving Film of Asphalt (Rolling Thin-Film Oven Test) ASTM D2872AASHTO T240

Determination of Asphalt Viscosity at Elevated Temperatures Using a Rotational Viscometer ASTM D4402AASHTO T316

Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel ASTM D6521AASHTO R28

Determining the Flexural Creep Stiffness of Asphalt Binder Using the Bending Beam Rheometer (BBR) ASTM D6648AASHTO 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 D7175AASHTO T315

Multiple Stress Creep Recovery (MSCR) Test of Asphalt Binder Using a Dynamic Shear Rheometer (DSR) ASTM D7405AASHTO 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 D6307AASHTO 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 TP79AASHTO PP61

Tests on Cutback and Emulsion

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

Rate of Spread of Coated Chippings Rate of Spread and Accuracy of Spread of Binder and Chippings

BS 598-108:1990 BS EN 12272-1:2002

Slurry Surfacing Test Methods: Consistency BS EN 12274-3:2002

Particle Charge of Cationic Emulsified Asphalts ASTM D244