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Evaluation of Indirect Tensile Test (IDT) Procedures for Low-Temperature Performance of Hot Mix Asphalt (2004) / Chapter Skim
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Appendix B - Equipment Configurations for Creep and Strength Testing of Hot Mix Asphalt Concrete at Low Temperatures
Pages 45-51

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From page 45...
... The NCHRP Project 9-29 Phase III Interim report included the recommendation that the low-temperature creep and strength testing required for the Superpave thermal cracking model should primarily be performed using uniaxial testing performed on the dynamic modulus master curve equipment as required in the pavement design guide developed in NCHRP Project 1-37A. However, as is made clear throughout this report, the presence of anisotropy in the creep compliance of asphalt concrete mixtures measured at low temperatures strongly suggests that the IDT test should be retained as the standard procedure, though some relatively minor revisions are needed in this method.
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From page 46...
... The SHRP IDT Creep and Strength Tests During SHRP, low-temperature cracking was identified as one of the major forms of distress in asphalt concrete pavements. A concerted effort was made to develop an effective mechanics-based approach to evaluate the resistance of asphalt concrete mixtures to this form of damage; the IDT creep and strength tests were the result (B1)
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From page 47...
... For this reason, suppliers of the frequency-sweep equipment to be used in characterizing mixtures for the pavement design guide developed in NCHRP Project 1-37A should be encouraged to include as an option the necessary capacity, hardware, and software for performing low-temperature creep and strength tests using the IDT procedure. Although it has some practical advantages, uniaxial testing does not provide data equivalent to that produced with the IDT test.
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From page 48...
... An initial review of the specifications for the dynamic modulus master curve test device (presented later in this appendix) has indicated that with only slight modifications, it could be used to perform low-temperature creep and strength tests for use in the Superpave thermal cracking model.
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From page 49...
... The changes proposed in Table B-1 are not substantial and should not be difficult to implement. USE OF DYNAMIC MODULUS MASTER CURVE TEST EQUIPMENT FOR LOW-TEMPERATURE CREEP AND STRENGTH TESTING A similar approach to the analysis presented in Appendix A for the IDT creep and strength test is presented below for uniaxial testing of asphalt concrete at low temperatures.
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From page 50...
... Although the increased static capacity required for lowtemperature creep and strength testing is substantial, it greatly increases the flexibility and capability of the dynamic modu Item Requirements for Dynamic Modulus Test Equipment for Generating Master Curves for Structural Design ENVIRONMENTAL CHAMBER Temperature range −10 to 60 °C Control accuracy To within ±0.5 °C of specified temperature LOADING SYSTEM Dynamic load 22.5 kN (5.0 kips) Contact load 5 % of test load Static load and peak dynamic load accuracy ±2 % of specified value Dynamic load accuracy Maximum standard error of 5 % Loading rate 0.01 to 25 Hz LOAD MEASUREMENT SYSTEM Range Equal to or greater than stall force of loading system actuator Accuracy ±1 % maximum for loads ranging from 2 to 100 % of the machine, when verified in accordance with ASTM E4 Resolution Shall comply with requirements of ASTM E4 AXIAL STRAIN TRANSDUCER Gage length 70 mm nominal Range 1 mm minimum Resolution Equal to or better than 0.0002 mm (7.8 micro-inch)
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From page 51...
... Based upon this review, the following conclusions and recommendations are made: • Several minor refinements in the IDT equipment specification are needed; revised equipment requirements are discussed in detail in Appendix A of this report and are summarized in Table B-1 of this appendix. • The dynamic modulus master curve test equipment needed for HMA characterization in the pavement design guide developed in NCHRP 1-37A is capable of properly performing low-temperature uniaxial creep tests with only minor modification.
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Key Terms

  • asphalt concrete
  • idt creep
  • master curve
  • strength tests
  • strength test

  • idt test
  • modulus master
  • test equipment
  • modulus test
  • curve test

  • strength testing
  • superpave centers
  • thermal cracking
  • low temperatures
  • nchrp project

  • pavement design
  • simple performance
  • performance tests
  • guide developed
  • test geometry

  • concrete mixtures
  • design guide
  • test procedures
  • superpave thermal
  • low temperature

  • idt strength
  • uniaxial test
  • loading rate
  • idt tests
  • tensile strength


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