Resilient Modulus Testing and Startup Procedures

1. Resilient Modulus Testing and Startup Procedures A Product Line

2. PRESENTATION OBJECTIVES What is the Resilient Modulus (Mr) Testing and Startup Product Line • Why Mr Testing and the Startup Procedures are Important • Development of the Mr Startup Procedure • How to Conduct the Mr Startup Procedure • Who Should Use the Mr Testing and Startup Product Line and Why • How to Get Information on the Mr Testing and Startup Product Line

3. FHWA LTPP Protocol P46, Resilient Modulus of Unbound Granular Base/Subbase Materials and Subgrade Soils LTPP Mr Start-up Procedure Product Line FHWA-RD-96-176, Resilient Modulus of Unbound Materials Laboratory Startup and Quality Control Procedure • FHWA Video Tape Series • Laboratory Resilient Modulus Testing: Is This the Right Time? • Laboratory Resilient Modulus Testing: Startup and Quality Control Procedure • Laboratory Resilient Modulus Testing: Sample Preparation and Test Procedure

4. Resilient Modulus Lab Tests Videotape 1 “Laboratory Resilient Modulus Testing: Is This the Right Time?” • 8 minutes • Explains resilient modulus and what it is used for. • Describes developments that have made the testing more consistent and easier to adopt. • Target Audience: Administrators and engineers

5. Resilient Modulus Lab Tests Videotape 2 “Laboratory Resilient Modulus Testing: Startup and Quality Control Procedure” • 15 minutes • Gives detailed definition of resilient modulus. • Explains the procedure developed to ensure that a lab is set up properly to conduct the test procedure and to collect accurate test results. • Target Audience: Laboratory managers and technicians

6. Resilient Modulus Lab Tests Videotape 3 “Laboratory Resilient Modulus Testing: Sample Preparation and Test Procedure” • 13 minutes • Describes each step in the resilient modulus test procedure, including how to prepare soil and aggregate samples. • Target Audience: Lab managers and technicians

7. PRESENTATION OBJECTIVES • What is the Resilient Modulus (Mr) Testing and Startup Procedure Product Line • Development of the Mr Startup Procedure • How to Conduct the Mr Startup Procedure • Who Should Use the Mr Testing and Startup Product Line and Why • How to Get Information on the Mr Testing and Startup Product Line Why Mr Testing and the Startup Procedures Are Important

8. Resilient Modulus 101 • AASHTO Definition: • “A measure of the elastic property of soil recognizing certain non-linear characteristics.” • Resilient Modulus = Mr • Resilient Modulus = elastic modulus (mod. of elasticity) • Resilient Modulus = stress/strain • Resilient Modulus = stiffness • Resilient modulus  strength

9. Typical Elastic Modulus Values (ksi) • PCC 3,000 – 6,000 • Asphalt Concrete 500 – 2,000 • Crushed Stone 20 – 40 • Silty Soils 5 – 20 • Clayey Soils 5 – 10

10. Usefulness of Resilient Modulus • Used to define fundamental material properties • Used in constitutive models • Used to predict stress, strain, and displacement • Used to develop performance models • Used in current AASHTO pavement design guide • Used in mechanistic design approach

11. The Resilient Modulus Startup Procedure • Verifies the ability of equipment and personnel to perform resilient modulus testing • Developed by LTPP to ensure consistent, repeatable and accurate results • Implemented in FHWA, state DOTs, academia, and industry

12. Benefits Of Mr Startup Procedure • Procedure useful to anyone conducting resilient modulus testing • Prepared for resilient modulus of soils but can be applied to asphalt • Generic procedure useful to anyone performing testing using servo-hydraulic test systems (i.e. complex modulus, creep, etc.)

13. PRESENTATION OBJECTIVES • What is the Resilient Modulus (Mr) Testing and Startup Procedure Product Line • Why Mr Testing and the Startup Procedures are Important • How to Conduct the Mr Startup Procedure • Who Should Use the Mr Testing and Startup Product Line and Why • How to Get Information on the Mr Testing and Startup Product Line Development of the Mr Startup Procedure

14. Testing and Protocol History • 1987 - Strategic Highway Research Program (SHRP) adopts resilient modulus testing • 1990 - Initial protocols developed • 1991 - Resilient Modulus testing began • 1992 - FHWA assumes leadership of LTPP • Early 1993 - SHRP Resilient Modulus Testing Ends

15. Data Problems:1993/1994 - SHRP data • Serious flaws found in the data • Large amount of data deemed unusable • Probable cause • faulty electronics • mechanical problems • operator error

16. Causes of Data Problems • Sample loading non-symmetrical • Sample loaded too long • Deformation occurs prior to loading * • Deformation impulse shorter than load impulse * • Deformation fluctuation • Deformation “flat-line” or clipping phenomenon

17. High Testing Variability and Low Confidence • Poor precision and bias • SHRP precision and bias testing yielded 100% variation between labs, 50% within lab • Many practitioners have no confidence in test results • Equipment standardization lacking

18. The Mr Testing Challenge • Significant modulus testing remained to be completed • Need for equipment and operator verification procedure established Result • P46 test procedure revised to reflect lessons learned • P46 startup procedure developed to address equipment/operator issues

19. The Startup Procedure Development Objectives • Develop a simple, efficient and inexpensive methodology to verify equipment performance and accuracy of a laboratory • Verify laboratory ability (personnel/equipment) to conduct P46 Resilient Modulus Tests

20. PRESENTATION OBJECTIVES • What is the Resilient Modulus (Mr) Startup Procedure Product Line • Why Mr Testing and the Startup Procedure is Important • Development of the Mr Startup Procedure • Who Should Use the Mr Startup Procedure and Why • How to Get Information on the Mr Startup Procedure How to Conduct the Mr Startup Procedure

21. Equipment • Oscilloscope • Function Generator • Strain Indicator • LVDT Modulator/Oscillator (optional) • NIST Traceable Proving Rings • Micrometer Calibrator • NIST Traceable Pressure Gauge

22. The 3-Phase Startup Process • Verification of Electronic System • Verification of Mechanical System • Verification of Laboratory Ability to Conduct P46 Resilient Modulus Test

23. Electronic System VerificationElectrical Method (Method 1) • Focuses on the signal path from the transducers to the digitized output data • Input: an electrical signal with known frequency and amplitude • Output: acquired digitized data • Compares input and output signals for a range in frequency

24. Electronic System VerificationMechanical Method (Method 2) • Focuses on the signal path from the transducers to the digitized output data • Input: a “reference” LVDT and the machine LVDT are exercised mechanically with known frequency and amplitude • Output: acquired digitized data and visual reference to oscilloscope • Compares input and output signals for a range in frequency • Note: new procedure, not documented in FHWA-RD-96-176, simpler than Method 1

25. Electronic System VerificationComponents Checked • Analog signal conditioning • Digitized signal processing • Transducers (load cells, LVDTs) • Signal filters • Various layers of data acquisition and control software • Acceptance Criteria • Matched input to output delays < .5 msec • Amplitude constant from 2 to 50 hz

26. The 3-Phase Startup Process • Verification of Electronic System • Verification of Mechanical System • Verification of Laboratory Ability to Conduct P46 Resilient Modulus Test

27. Mechanical System Verification • Focuses on the performance capability of the laboratory equipment • Uses NIST traceable calibrated proving rings and other measurement devices

28. Mechanical System Verification Components • LVDT Calibration • Load Cell Zero • Load Cell Calibration Certificates • Load Cell Cal. Verification • Dynamic Response • Phase Angles • Triaxial Pressure Chamber