The Superpave Gyratory The Superpave Gyratory Compactor How do we use Compactor How do we use

it.it.

John D’AngeloJohn D’Angelo

Office of Pavement Technology US Office of Pavement Technology US Federal Highway AdministrationFederal Highway Administration

BackgroundBackground

• SHRP A-001 ContractSHRP A-001 Contract– Development of Superpave Mix Design Development of Superpave Mix Design

ProcedureProcedure•Gyratory Compactor ExperimentsGyratory Compactor Experiments

– Conducted at Asphalt InstituteConducted at Asphalt Institute

– Included rotational speed, NIncluded rotational speed, Ndesigndesign, sensitivity , sensitivity experimentsexperiments

– Comparison between prototype and production SGCComparison between prototype and production SGC Led to discovery of angle sensitivityLed to discovery of angle sensitivity Tolerance of Tolerance of ±0.02 degrees±0.02 degrees

Differences in SGCs –Differences in SGCs –NATC MixturesNATC Mixtures

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

1 2 3Compactor

Air

Vo

ids

, %

Prototype

Measurement of the Internal Measurement of the Internal Angle of GyrationAngle of Gyration

• Significant Differences in Air VoidsSignificant Differences in Air Voids– Difference in Design AC Could be as Difference in Design AC Could be as

Much as 0.8% Asphalt ContentMuch as 0.8% Asphalt Content

• Angle of GyrationAngle of Gyration– All Compactors set to 1.25° ExternallyAll Compactors set to 1.25° Externally– What is the Internal Angle of Gyration?What is the Internal Angle of Gyration?

•Frame compliance?Frame compliance?

4. APPARATUS4. APPARATUS

Superpave Gyratory CompactorSuperpave Gyratory Compactor – … – … The compactor shall tilt the specimen The compactor shall tilt the specimen molds at an molds at an externalexternal angle of angle of 1.25°1.25°++0.02° 0.02° oror an average internal an average internal angle of 1.16°angle of 1.16°+ + 0.02° in accordance 0.02° in accordance with AASHTO T312. The compactor with AASHTO T312. The compactor shallshall gyrate the specimens mold at a gyrate the specimens mold at a rate of 30.0 + 0.5 gyrations per rate of 30.0 + 0.5 gyrations per minute… minute…

4.1

Internal Angle of GyrationInternal Angle of Gyration

• Internal Angle of GyrationInternal Angle of Gyration– Development of the Dynamic Angle Development of the Dynamic Angle

Validator (DAV) or Angle Validation Kit Validator (DAV) or Angle Validation Kit (AVK)(AVK)•Wireless UnitWireless Unit

•Drop into mold either before or after adding Drop into mold either before or after adding mixmix

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

Dynamic Angle ValidatorDynamic Angle Validator

DAV CalibrationDAV Calibration

AVG

T1.150

1.10

1.15

1.20

1.25

1.30

1.35

1.40

20

30

40

50

60

70

80

90

10

0

11

0

12

0

13

0

14

0

Specimen Height (mm)

Inte

rna

l An

gle

of G

yra

tion

(d

eg

ree

s)

Average Internal AngleTop Angle (individual AVK result)Top Angle (best fit)Bottom Angle (individual AVK result)Bottom Angle (best fit)target height (115 mm)angle at target height

After adjustment using the DAV Kit

Close Large Chart

Internal Angle of GyrationInternal Angle of Gyration

• DAVDAV– Validate Differences in SGCsValidate Differences in SGCs

•Demonstrated that internal angle of gyration Demonstrated that internal angle of gyration could be different even though external angle could be different even though external angle was the same.was the same.

– CalibrationCalibration•Potentially time-intensivePotentially time-intensive

– Up to 1 day for a calibrationUp to 1 day for a calibration

•Affected by mixture stiffness?Affected by mixture stiffness?– Requiring recalibration for different mix typesRequiring recalibration for different mix types

Forces Acting in a Mold During Forces Acting in a Mold During Gyratory CompactionGyratory Compaction

Mechanical Simulation of an Mechanical Simulation of an Asphalt Mixture – RAMAsphalt Mixture – RAM

RAM – Rapid Angle Measurement Device (Pine)

RAM OperationsRAM Operations

Increasing Ring Diameter =Increasing Mix Eccentricity

Mechanical Simulation of an Mechanical Simulation of an Asphalt Mixture – HMSAsphalt Mixture – HMS

HMS – Hot-Mix Simulator (TestQuip)

Purpose of ResearchPurpose of Research

• ObjectivesObjectives– Improve the determination and Improve the determination and

calibration of the dynamic internal angle calibration of the dynamic internal angle of gyration for the Superpave gyratory of gyration for the Superpave gyratory compactor using mechanical mixture compactor using mechanical mixture simulation devicessimulation devices•Reduce time for calibrationReduce time for calibration

• Improve reproducibility between different labsImprove reproducibility between different labs

•Recommend revisions to AASHTO T312Recommend revisions to AASHTO T312

Research Plan – Task 1Research Plan – Task 1

• Determine the Effect of Mix Determine the Effect of Mix Eccentricity on Internal Angle of Eccentricity on Internal Angle of GyrationGyration

SGC-A

SGC-B

Mix e

Internal Angle

Acceptable Range of Internal Angle

Internal Angle

Research Plan – Task 2Research Plan – Task 2

• Using a Wide Variety of Mixtures…Using a Wide Variety of Mixtures…– What is the relationship between What is the relationship between

mixture eccentricity and stiffness?mixture eccentricity and stiffness?– What is an “average” or representative What is an “average” or representative

mixture eccentricity?mixture eccentricity?– Is there a standard mixture eccentricity Is there a standard mixture eccentricity

that can be used to minimize variation that can be used to minimize variation in the percentage of air voids in in the percentage of air voids in specimens produced by different SGCs?specimens produced by different SGCs?

Research Plan – Task 3Research Plan – Task 3

• Using Mechanical Simulation Devices Using Mechanical Simulation Devices in the Calibration Processin the Calibration Process– IssuesIssues

•Necessity of heated molds?Necessity of heated molds?

Testing Testing AgencyAgency

Frame Stiffness (Deg / N-m)Frame Stiffness (Deg / N-m)

Superpave Gyratory Compactor (SGC) ModelSuperpave Gyratory Compactor (SGC) Model

PinePineAFG125xAFG125x

PinePineAFG1AFG1

PinePineAFGB1AFGB1

(Brovold)(Brovold)Troxler Troxler

41404140TroxlerTroxler

41414141 ServoPacServoPac

Univ. of ArkansasUniv. of Arkansas(Stiffness Study)(Stiffness Study) 0.000310.00031 0.000340.00034 0.000360.00036 0.001090.00109 0.000630.00063   

Univ. of ArkansasUniv. of Arkansas(RAM ILS)(RAM ILS) 0.000460.00046    0.000250.00025 0.001390.00139 0.000580.00058   

Univ. of ArkansasUniv. of Arkansas(RAM-DAV/HMS Study)(RAM-DAV/HMS Study) 0.000370.00037 0.000470.00047 0.000310.00031 0.001270.00127 0.000540.00054   

Florida DOTFlorida DOT(used by permission)(used by permission) 0.000330.00033    0.000410.00041 0.001720.00172    0.000410.00041

InstroTekInstroTek(used by permission)(used by permission)

0.000470.00047 0.000500.00050 0.000550.00055 0.001760.00176 0.001800.00180   

         0.001360.00136 0.001220.00122   

         0.001320.00132      

Mean ValueMean Value 0.000390.00039 0.000440.00044 0.000380.00038 0.001420.00142 0.000950.00095 0.000410.00041

Standard DeviationStandard Deviation 0.0000740.000074 0.0000850.000085 0.0001140.000114 0.0002420.000242 0.0005480.000548 N/AN/A

Coefficient ofCoefficient ofVariation (%)Variation (%) 19.019.0 19.519.5 30.330.3 17.117.1 57.557.5 N/AN/A

Frame Stiffness Measures – RAM only

Thanks!Thanks!