AASHTO T 344-2012 Standard Method of Test for Evaluation of Superpave Gyratory Compactor (SGC) Internal Angle of Gyration Using Simulated Loading.pdf

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1、Standard Method of Test for Evaluation of Superpave Gyratory Compactor (SGC) Internal Angle of Gyration Using Simulated Loading AASHTO Designation: T 344-121,2ASTM Designation: D7115-05 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washin

2、gton, D.C. 20001 TS-2d T 344-1 AASHTO Standard Method of Test for Evaluation of Superpave Gyratory Compactor (SGC) Internal Angle of Gyration Using Simulated Loading AASHTO Designation: T 344-121,2ASTM Designation: D7115-05 1. SCOPE 1.1. This practice covers the procedure for the evaluation of the S

3、uperpave gyratory compactor (SGC) internal angle of gyration using an instrument capable of simulating loading conditions similar to those created by a hot mix asphalt (HMA) specimen. 1.2. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to add

4、ress all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standard: T 312, Pr

5、eparing and Determining the Density of Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor 3. TERMINOLOGY 3.1. Definitions: 3.1.1. external anglethe angle formed between the external mold diameter and a stationary reference/axis of the machine frame. 3.1.2. internal anglethe angle

6、 formed between the internal mold diameter and a mold end plate as a mold is gyrated in an SGC. 3.1.3. top internal anglethe angle formed between the internal mold diameter and the upper mold end plate as a mold is gyrated in an SGC. 3.1.4. bottom internal anglethe angle formed between the internal

7、mold diameter and the lower mold end plate as a mold is gyrated in an SGC. 3.1.5. effective internal anglethe average of the top internal angle and the bottom internal angle. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violatio

8、n of applicable law.TS-2d T 344-2 AASHTO 3.1.6. tilting momenta force (F) acting at one end of an SGC mold platen in a direction parallel to the axis of gyration, but acting at some distance (e) away from that axis. The tilting moment at one end of the mold platen is computed as the product of this

9、distance (e) and force (F). 3.1.7. total momentthe sum total (M) of the tilting moment acting at the top of the mold and the tilting moment acting at the bottom of the mold. 3.1.8. eccentricitythe distance (e) away from the axis of gyration at which a force (F) is acting at one end of an SGC mold. T

10、his use of the term eccentricity is consistent with previous published reports describing the mechanics of gyratory compaction. 3.1.9. standard SGC volumetric specimena standard-sized HMA specimen prepared using an SGC for purposes of volumetric mix design. Such a standard specimen, prepared in acco

11、rdance with T 312, has a diameter of 150 mm and a final compacted height of 115 5 mm. 4. SUMMARY OF PRACTICE 4.1. The internal angle of gyration of an SGC is measured dynamically with an instrument inserted into the SGC mold. 4.2. A load (moment) is induced on the SGC while the internal angle is sim

12、ultaneously measured. The simulated loading conditions are similar to those created by compaction of a standard SGC volumetric specimen. 4.3. The internal angles at each end of the mold are measured and then averaged to obtain the effective internal angle of gyration. 5. SIGNIFICANCE AND USE 5.1. SG

13、Cs are used to produce hot mix asphalt (HMA) mixture specimens in the laboratory to assess and predict pavement performance. In the fabrication of an SGC specimen, loose HMA is placed inside a metal mold, which is then placed into an SGC. A constant consolidation pressure is applied to the sample wh

14、ile the mold gyrates at a nominally constant angle (referred to as the angle of gyration) and rate. Consistency in the density of the HMA specimens produced is very important to the validity of the tests performed. Specimens of a consistent density are produced when an SGC maintains a constant press

15、ure and a known constant angle of gyration during the compaction process. 5.2. There are several manufacturers and models of SGC. Each model employs a unique method of setting, inducing, and maintaining the angle of gyration. Each model also employs a unique calibration system to measure the externa

16、l angle of gyration. These existing calibration systems cannot be used universally on all of the different SGC models commercially available. Inconsistencies in HMA specimens produced on different SGC models have been attributed to variations in the angle of gyration. 5.3. This practice describes in

17、struments and processes that can be used to independently measure the internal angle of gyration of any manufacturers SGC model under simulated loading conditions. The external shape of the instrument chassis assures that the points of physical contact between the mold end plates and the instrument

18、occur at a fixed and known distance away from the axis of gyration. As a result, the vertical load is applied at these fixed points, creating tilting moments at each end of the mold. 5.4. Unless otherwise specified, tilting moments corresponding to an eccentricity of 22 mm shall be used to simulate

19、the loading conditions of a standard SGC volumetric specimen. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d T 344-3 AASHTO 6. INTERFERENCES 6.1. Debris on the SGC mold, base plates, ram head, rea

20、ction surfaces, or on the instrument can cause errant measurement results. Extreme care should be taken to thoroughly clean the SGC, mold, instrument, and any work areas that will be utilized during the measurement procedure. Scarring or irregular surfaces on mold walls and end plates is also known

21、to cause incorrect results. Do not use any equipment that shows signs of damage. The precision required in the execution of this practice necessitates that extreme care must be taken to avoid errors from damaged or improperly maintained equipment. 7. APPARATUS 7.1. The instrument should be capable o

22、f being gyrated inside an SGC mold that induces tilting moments at each end of the SGC mold while simultaneously measuring an internal angle of gyration. 7.1.1. Data AcquisitionThe timing of the data acquisition system may be automatically triggered by the start of the gyration process. Provision fo

23、r excluding a known number of initial gyrations from the angle measurement may be provided (initial delay period), and the angle shall be measured throughout a known number of subsequent gyrations (data acquisition period). The durations of the initial delay and the data acquisition periods may be p

24、rogrammable or fixed. 7.1.2. Display OptionsThe angle measurement result(s) may be viewable on a display built into the instrument chassis and/or retrievable from the instrument via a communications port. 7.1.3. Temperature MeasurementThe instrument may optionally have a means for displaying, record

25、ing, or otherwise indicating its internal temperature during the angle measurement process. 7.1.4. Static Angle GaugeA NIST-traceable angle gauge device machined with one or more known angles and used to calibrate and verify the calibration of the angle measurement instrument. 7.1.5. Wear Protection

26、 PlatesThin steel plates (optional) that protect the SGC mold end plates from any cosmetic damage by the contact rings. 7.2. Superpave Gyratory Compactor (SGC)And associated equipment as described in T 312. The SGC shall be in good repair, with the compaction pressure, specimen height measurement sy

27、stem, and gyration rate verified to be within specifications. The mechanisms used to induce and maintain the angle of gyration shall be set and maintained within the manufacturers guidelines. 7.2.1. The SGC molds, mold end plates, base platens, and ram head surface smoothness shall be confirmed to b

28、e within the specifications of T 312. Any equipment not meeting these requirements shall not be used. 8. HAZARDS 8.1. Use standard safety precautions and protective clothing for working in a hot-mix asphalt laboratory. 2015 by the American Association of State Highway and Transportation Officials.Al

29、l rights reserved. Duplication is a violation of applicable law.TS-2d T 344-4 AASHTO 9. CALIBRATION AND STANDARDIZATION 9.1. The angle measurement instrument requires periodic verification, calibration, or both. The system shall be standardized prior to initial use and at least once every 12 months.

30、 This annual verification is generally considered a factory calibration and includes the following: 9.1.1. Verification of the static angle gauge with a NIST-traceable measurement system. 9.1.2. Verification of the angle measurement instrument. 10. PREPARATION OF APPARATUS 10.1. Before each use of t

31、he angle measurement instrument (i.e., on a daily basis), verify the angle measurement system using the static angle gauge. The static angle gauge, which can apply one or more known angles to the instrument, is used to confirm that the instrument is operating within calibration. Note 1The instrument

32、 and the static angle gauge must be at the same uniform, stable temperature for the verification to be accurate. 10.2. Be sure the probe tips and contact rings on the angle measurement instrument are free of debris. 10.3. Prepare a clean compaction mold assembly. Note 2Accumulation of HMA on one or

33、more of the mold surfaces, mold end plates, base platens, or ram head surfaces directly impacts the instruments ability to accurately measure the angle of gyration. Use mineral spirits or another appropriate solvent to clean these surfaces. 10.4. If the angle measurement is to be made at an elevated

34、 temperature, place the SGC mold in an oven at the desired temperature 5C for a minimum of 45 min prior to making the first angle measurement. Do not place the angle measurement instrument in the oven. Note 3The SGC manufacturer may recommend measurement of the angle at an elevated temperature for t

35、hose SGC models where the angle changes with mold temperature. Note 4Instruments typically have a limited operating temperature range. After use in a hot mold, the angle measurement instrument can be cooled by using a fan to blow ambient air over the instrument or by placing it in front of an air co

36、nditioner. Elevating the instrument above the table surface so as to permit maximum airflow over the entire instrument will increase the rate of cooling. Do not cool the instrument below room temperature. 10.5. Verify the settings on the compactor. Unless noted otherwise, the SGC shall be initialize

37、d to provide specimen compaction using a consolidation pressure of 600 18 kPa and a gyration rate of 30 0.5 rpm. 10.6. Set the number of gyrations on the SGC in accordance with the recommendations of the manufacturer of the angle measurement instrument. 11. PROCEDURE 11.1. The average internal angle

38、 is based on four individual angle measurements as follows: 11.1.1. The top internal angle is measured twice. If the two results do not match within 0.02 degrees, discard the results and repeat this step. 2015 by the American Association of State Highway and Transportation Officials.All rights reser

39、ved. Duplication is a violation of applicable law.TS-2d T 344-5 AASHTO 11.1.2. The bottom internal angle is measured twice. If the two results do not match within 0.02 degrees, discard the results and repeat this step. 11.2. Each of the four individual angle measurements is performed as follows: 11.

40、2.1. Arm the angle measurement instrument for collecting data. 11.2.2. Place the angle measurement instrument inside the SGC mold. Orient the instrument probes or reference base as appropriate to measure the top or bottom angle. Note 5The operator may wish to use a mold extruder to elevate the botto

41、m mold plate to a position where insertion of the angle measurement instrument into the SGC mold is easier. 11.2.3. Place the SGC mold inside the SGC. Note 6For some SGCs, it may be more convenient to first place the mold in the SGC and then place the angle measurement instrument in the mold. 11.2.4

42、. Initiate the compaction process. For most SGCs, this is an automatic process consisting of pressing a button to start the compaction process. The SGC automatically applies the ram pressure, induces the angle, and gyrates the mold to the specified number of gyrations. Note 7Certain models of Superp

43、ave gyratory compactor may exhibit erratic behavior when applying compaction pressure to a simulated load device. Consult SGC manufacturer recommendations regarding the use of simulated load devices and specific procedures for initiating and completing the compaction process. 11.2.5. Remove the angl

44、e measurement instrument from the SGC mold. Note 8Use caution when removing the instrument, especially when using a power extruder. Take care that the instrument does not get caught or damaged during the extrusion process. 11.2.6. Record the angle result reported by the instrument (to the nearest 0.

45、01 degree). Record which angle (top or bottom) and which replicate (1 or 2) was measured. 12. CALCULATION 12.1. Calculate the average top internal angle as follows: (top internal angle 1 + top internal angle 2)average top internal angle2= (1) 12.2. Calculate the average bottom internal angle as foll

46、ows: (bottom internal angle 1 + bottom internal angle 2)average bottom internal angle2= (2) 12.3. Calculate the effective internal angle as follows: (average top internal angle + average bottom internal angle)effective internal angle2= (3) 13. REPORT 13.1. The report shall contain the following info

47、rmation: 13.1.1. SGC informationManufacturer, model number, serial number, owner, location, number of gyrations, and consolidation pressure used during the angle measurement process; 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a

48、violation of applicable law.TS-2d T 344-6 AASHTO 13.1.2. Angle measurement instrument identificationManufacturer, model number, serial number, date of calibration; 13.1.3. Due date for next calibration and eccentricity; Note 9Consult the instrument manufacturers manual for determination of the appli

49、ed eccentricity for the particular instrument used. 13.1.4. Results from each of the individual angle measurementsExpress each angle measurement to the nearest 0.01 degree, with notations indicating top or bottom angle; and 13.1.5. Effective internal angle. 13.2. The technician performing the test shall sign and date the report. Note 10A sample report is provided in Appendix X1. 14. PRECISION AND BIAS 14.1. PrecisionThe precision is based on an ASTM Interlaboratory Study (ILS #151) that was conducted in 2007. ILS #151 involved 27 laborato