Ruggedness Testing of the Dynamic Modulus and Flow Number Tests with the Simple Performance Tester (2008) / Chapter Skim
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E1 A P P E N D I X E Final Version of the SPT Equipment Specifications
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E2 NCHRP Project 9-29 Simple Performance Tester for Superpave Mix Design Equipment Specification For The Simple Performance Test System LIMITED USE DOCUMENT The information contained in this Document is regarded as fully privileged. Dissemination of information included herein must be approved by the NCHRP.
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B Minimum Testing Program For Comparison of a Non-Standard Specimen Deformation Measuring System to the Standard Specimen Deformation Measuring System.....................................................................................................38 1
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1.3 Flow Time Test. In this test, the specimen is subjected to a constant axial compressive load at a specific test temperature.
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0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0 1000 2000 3000 4000 5000 6000 Load Cycle Pe rm an en t S tra in , % 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 0.0040 0.0045 0.0050 Pe rm an en t S tra in R at e, % p er C yc le Permanent Strain Permanent Strain Rate Flow Number = Minimum Permanent Strain Rate Figure 2. Schematic of Flow Number Test Data.
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compressive stress of various frequencies. The applied stresses and resulting axial strains are measured as a function of time and used to calculate the dynamic modulus and phase angle.
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2.10 Dynamic Stress. Sinusoidal deviator stress applied during the Dynamic Modulus Test.
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above the floor. 4.5 The load frame, environmental chamber and computer control system for the Simple Performance Test System shall operate on single phase 115 or 230 VAC 60 Hz electrical power.
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The requirements for each of the simple performance tests are listed below. Test Type of Loading Capacity Rate Flow Time Ramp, constant 10 kN (2.25 kips)
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across any diameter. 7.0 Load Measuring System 7.1 The Simple Performance Test System shall include an electronic load measuring system with full scale range equal to or greater than the stall force for the actuator of the compression loading machine.
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load. 9.0 Specimen Deformation Measuring System 9.1 The Simple Performance Test System shall include a glued gauge point system for measuring deformations on the specimen over a gauge length of 70 mm (2.76 in)
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over the 1 mm range when verified in accordance with ASTM D 6027. 9.6 The axial deformation measuring system shall be designed for rapid specimen installation and subsequent testing.
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10.3 Confining pressure shall be controlled by the computer control and data acquisition system. The confining pressure control system shall have the capability to maintain a constant confining pressure throughout the test within +/- 2 percent of the desired pressure.
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11.4 The environmental chamber shall be designed for rapid installation of the test specimen and subsequent equilibration of the environmental chamber temperature to the target test temperature. Specimen instrumentation, installation, application of confining pressure, and temperature equilibration shall take no longer than 5 minutes over the complete range of temperatures.
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12.3 Flow Time Test Control and Data Acquisition 12.3.1 The control system shall control the deviator stress, and the confining pressure within the tolerances specified in Sections 5 and 10.2 12.3.2 The control system shall ramp the deviator stress from the contact stress condition to the creep stress condition in 0.5 sec. 12.3.3 Zero time for data acquisition and zero strain shall be defined as the start of the ramp from contact stress to creep stress.
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12.3.6 The Flow Time Test Software shall include a screen to input test and file information including: 1. Project Name 2.
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8. Time and corresponding measured deviator stress, measured confining pressure, measured temperature, measured axial strain, and computed rate of change of strain.
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Plot of rate of change of axial strain versus time with the flow time indicated. 12.4 Flow Number Test Control and Data Acquisition 12.4.1 The control system shall control the deviator stress, and the confining pressure within the tolerances specified in Sections 5 and 10.2 12.4.2 The control system shall be capable of applying an initial contact stress, then testing the specimen with the user specified cyclic deviator stress.
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The rate of change of permanent axial strain shall be computed in accordance with the algorithm presented in Section 13. 12.4.10 If at any time during the test, the peak deviator stress, standard error of the applied load, confining pressure, or temperature exceed the tolerances listed below, the Flow Number Test Software shall display a warning and indicate the parameter that exceeded the control tolerance.
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12.4.13 The Flow Number Test Software shall provide a one page hard copy output with the following: 1. Test information supplied by the user in Section 12.4.7.
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12.5.9 During the conditioning and testing, the Dynamic Modulus Test Software shall provide a real-time display of the axial stress, and the axial strain measured individually by the transducers. 12.5.10 If at any time during the conditioning and loading portion of the test, confining pressure, temperature, or average accumulated permanent strain exceed the tolerances listed below, the Dynamic Modulus Test Software shall display a warning and indicate the parameter that exceeded the control tolerance.
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, % • The uniformity coefficient for the deformations, UA % • The uniformity coefficient for the deformation phase angles, Uθ , degrees. The user should be provided options to save this data to data file and/or produce a hard copy output.
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12.5.13 The Dynamic Modulus Test Software shall provide the capability of retrieving data files and exporting them to an ASCII comma delimited file for further analysis. 12.5.14 For each loading frequency, the Dynamic Modulus Test Software shall provide a one page hard copy output with the following.
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13.0 Computations 13.1 Flow Time Test 13.1.1 The Flow Time is defined as the time corresponding to the minimum rate of change of axial strain during a creep test. The flow time is found by fitting the model described in Section 13.1.2 to the axial strain data using nonlinear least squares, then determining the inflection point from the second derivative of the model described in section 13.1.4.
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13.1.6 The Flow Time is reported as the time when the second derivative of the axial strain model, Equation 6, changes from negative to positive. 13.2 Flow Number Test 13.2.1 The Flow Number is defined as the cycle corresponding to the minimum rate of change of axial permanent strain during a repeated load test.
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. In the typical arrangement, there will be m = 3 transducers: the first transducer will be a load cell, and transducers 2 and 3 will be specimen deformation transducers.
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E28 26 13.3.2 The calculation proceeds as follows. First, the data for each transducer are centered by subtracting from the measured data the average for that transducer: j ji ji Y Y Y − = ' (10)
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( 2 1 ^ j n i ji ji j Y n−4 Y Y Y se (18) Where: θ j = Phase angle for transducer j , degrees | Y j *
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This produces values for the phase angle, and standard errors for each transducer output. The phase angles given by Equation 13 represent absolute phase angles, that is, θ j is an arbitrary value indicating the angle at which data collection started.
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= Average standard error for all deformation transducers, % U A = Uniformity coefficient for deformation amplitude, % U θ = Uniformity coefficient for deformation phase, degrees
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A NIST traceable reference thermal detector with resolution equal to or better than the temperature sensor shall be used. 14.5 Verification of the dynamic performance of the force and specimen deformation measuring systems shall be performed by loading a proving ring or similar verification device with the specimen deformation measuring system attached.
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15.0 Verification of Normal Operation 15.1 The manufacturer shall develop and document procedures for verification of normal operation for each of the systems listed in Section 14.3, and the dynamic performance verification discussed in Section 14.5. It is anticipated that these verification procedures will be performed by the operating technician on a frequent basis.
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E34 32 Appendix A Specification Compliance Test Methods for the Simple Performance Test System
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Transducer Accuracy 8.4 Independent deflection verification (See verification procedures below) Load Mechanism Compliance and Bending 8.5 Measure on steel specimens with various degrees of lack of parallelism Configuration of Specimen Deformation Measuring System 9.1 Visual Gauge Length of Specimen Deformation Measuring System 9.1 Measure Transducer Range 9.2 Independent deflection verification (See verification procedures below)
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Transducer Accuracy 9.4 Independent deflection verification (See verification procedures below) Specimen Deformation System Complexity 9.5 Trial Confining Pressure Range 10.1 and 10.5 Independent pressure verification (See verification procedures below)
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3.0 Deflection and Specimen Deformation Measuring System Static Verification 3.1 Perform verification of the deflection and specimen deformation measuring systems in accordance with ASTM D 6027 Test Method B 3.2 The micrometer used shall conform to the requirements of ASTM E-83.
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4.6 If readings are beyond tolerance, adjust the device according to manufacturers specifications and repeat the dual applications of pressure as described above to complete verification. 5.0 Temperature Measuring System Verification 5.1 Verification of the temperature measuring system will be performed using a using a NIST traceable reference thermal detector that is readable and accurate to 0.1 oC.
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6.5 The verification device will also be used to check the phase difference between the load and specimen deformation measuring system. The phase difference shall be less than 1 degree.
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E40 38 Appendix B Minimum Testing Program For Comparison of a Non-Standard Specimen Deformation Measuring System to the Standard Specimen Deformation Measuring System
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140 (20 psi) 10, 1, and 0.1 1.4 Tests on twelve independent specimens will be performed with each specimen deformation measuring system.
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Confinement, kPa (psi) Specimen Deformation System Standard 1 25 (77)
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( 2 12 12 ∑ = − = i i yy s (B2) where: y = sample mean s 2 = sample variance yi = measured values 5.0 Statistical Hypothesis Testing 5.1 For each combination of temperature, confining pressure, and frequency of loading test the equality of variances between the standard specimen deformation system and the proposed specimen deformation measuring system using the F-test described below.
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5.3 If the results conclude the variance is greater for the proposed measuring for any of the combinations of temperature, confinement, and loading frequency tested, then the proposed measuring system is unacceptable. 5.4 For combinations of temperature, confinement, and loading frequency where equality of variances is confirmed by the hypothesis test in Item 5.1, test the equality of means between the standard specimen deformation system and the proposed specimen deformation measuring system using the t-test described below.
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6.4 Summary tables of dynamic modulus, phase angle, and data quality indicators for each combination of temperature, confining pressure, and loading frequency for the two measuring systems. 6.5 Summary tables of the mean and variance of the dynamic modulus and phase angle for each combination of temperature, confining pressure, and loading frequency for the two measuring systems.
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