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The Superpave Gyratory Compactor How do we use it. John DAngelo Office of Pavement Technology US Federal Highway Administration.

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Presentation on theme: "The Superpave Gyratory Compactor How do we use it. John DAngelo Office of Pavement Technology US Federal Highway Administration."— Presentation transcript:

1 The Superpave Gyratory Compactor How do we use it. John DAngelo Office of Pavement Technology US Federal Highway Administration

2 Compaction The goal of a laboratory compaction device is to fabricate a specimen for volumetric and/or physical characterization… The goal of a laboratory compaction device is to fabricate a specimen for volumetric and/or physical characterization…

3 Standard Method of Test for Preparing and Determining the Density of Hot-Mix Asphalt (HMA) Specimens by Means of the Superpave Gyratory Compactor AASHTO Designation: T

4 Are they all the same?

5 Background SHRP A-001 Contract SHRP A-001 Contract –Development of Superpave Mix Design Procedure Gyratory Compactor Experiments Gyratory Compactor Experiments –Conducted at Asphalt Institute –Included rotational speed, N design, sensitivity experiments –Comparison between prototype and production SGC Led to discovery of angle sensitivity Led to discovery of angle sensitivity Tolerance of ±0.02 degrees Tolerance of ±0.02 degrees

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7 Differences in SGCs – NATC Mixtures Compactor Air Voids, % Prototype

8 Measurement of the Internal Angle of Gyration Significant Differences in Air Voids Significant Differences in Air Voids –Difference in Design AC Could be as Much as 0.8% Asphalt Content Angle of Gyration Angle of Gyration –All Compactors set to 1.25° Externally –What is the Internal Angle of Gyration? Frame compliance? Frame compliance?

9 4. APPARATUS Superpave Gyratory Compactor – … The compactor shall tilt the specimen molds at an external angle of 1.25°+0.02° or an average internal angle of 1.16°+ 0.02° in accordance with AASHTO T312. The compactor shall gyrate the specimens mold at a rate of gyrations per minute… 4.1

10 Internal Angle of Gyration Internal Angle of Gyration Internal Angle of Gyration –Development of the Dynamic Angle Validator (DAV) or Angle Validation Kit (AVK) Wireless Unit Wireless Unit Drop into mold either before or after adding mix Drop into mold either before or after adding mix

11 Dr. Kevin Hall, Evaluating the Superpave Gyratory Compactor Internal Angle of Gyration Using Simulated Loading, submitted to AAPT2005 Dynamic Angle Validator

12 DAV Calibration

13 Internal Angle of Gyration DAV DAV –Validate Differences in SGCs Demonstrated that internal angle of gyration could be different even though external angle was the same. Demonstrated that internal angle of gyration could be different even though external angle was the same. –Calibration Potentially time-intensive Potentially time-intensive –Up to 1 day for a calibration Affected by mixture stiffness? Affected by mixture stiffness? –Requiring recalibration for different mix types

14 Issue The DAV procedure, although effective, is labor intensive and time consuming requiring up to a day for the required angle measurements and compactor calibration The DAV procedure, although effective, is labor intensive and time consuming requiring up to a day for the required angle measurements and compactor calibration

15 Forces Acting in a Mold During Gyratory Compaction

16 Mechanical Simulation of an Asphalt Mixture – RAM RAM – Rapid Angle Measurement Device (Pine)

17 RAM Operations Increasing Ring Diameter = Increasing Mix Eccentricity

18 Mechanical Simulation of an Asphalt Mixture – HMS HMS – Hot-Mix Simulator (TestQuip)

19 Purpose of Research Objectives Objectives –Improve the determination and calibration of the dynamic internal angle of gyration for the Superpave gyratory compactor using mechanical mixture simulation devices Reduce time for calibration Reduce time for calibration Improve reproducibility between different labs Improve reproducibility between different labs Recommend revisions to AASHTO T312 Recommend revisions to AASHTO T312

20 Research Plan – Task 1 Determine the Effect of Mix Eccentricity on Internal Angle of Gyration Determine the Effect of Mix Eccentricity on Internal Angle of Gyration SGC-A SGC-B Mix e Internal Angle Acceptable Range of Internal Angle Internal Angle

21 Research Plan – Task 2 Using a Wide Variety of Mixtures… Using a Wide Variety of Mixtures… –What is the relationship between mixture eccentricity and stiffness? –What is an average or representative mixture eccentricity? –Is there a standard mixture eccentricity that can be used to minimize variation in the percentage of air voids in specimens produced by different SGCs?

22 Research Plan – Task 3 Using Mechanical Simulation Devices in the Calibration Process Using Mechanical Simulation Devices in the Calibration Process –Issues Necessity of heated molds? Necessity of heated molds?

23 Testing Agency Frame Stiffness (Deg / N-m) Superpave Gyratory Compactor (SGC) Model Pine AFG125x Pine AFG1 Pine AFGB1 (Brovold) Troxler 4140 Troxler 4141 ServoPac Univ. of Arkansas (Stiffness Study) Univ. of Arkansas (RAM ILS) Univ. of Arkansas (RAM-DAV/HMS Study) Florida DOT (used by permission) InstroTek (used by permission) Mean Value Standard Deviation N/A Coefficient of Variation (%) N/A Frame Stiffness Measures – RAM only

24 Thanks!


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