STP561

    Summary of Complex Modulus Laboratory Test Procedures and Results

    Published: Jan 1974


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    Abstract

    The fundamental properties of an asphalt mixture are an important input to the new design procedures being developed. The complex modulus test, which measures both elastic and viscous material properties, is one of the several tests available for use with these procedures. In order to use these test results for design, it is necessary to assume that the mixture exhibits both linear and isotropic behavior. A review of current literature is presented which shows both assumptions valid for the elastic properties of an asphalt mixture under certain limiting conditions. The literature review is also used to provide background information for the development of a standard test method by defining the effect of test variables on complex modulus results.

    The results of a study of complex modulus data from both cored specimens and laboratory molded specimens are used to determine testing variability associated with various testing strategies. The testing error for the elastic part of the complex modulus, as defined by the coefficient of variation is equal to 4 percent for cored specimens and 8 percent for laboratory molded specimens. The variation between specimens was 8 and 17 percent, respectively, for laboratory molded and field cored specimens. Based on these results, a testing strategy consisting of three specimens tested twice at each test condition for laboratory molded specimens, and six specimens tested once at each test condition for cored specimens is recommended.

    The final section of the paper develops a method of predicting the elastic component of complex modulus. An equation is presented which can be used to predict this value from the results of the flexural fatigue tests.

    Keywords:

    fatigue tests, flexible pavements, dynamic modulus of elasticity, phase lag, elastic properties, viscoelasticity, isotropy, linearity, stiffness, stresses, strains, design, test equipment, coefficient of variation


    Author Information:

    Witczak, MW
    Research engineer and assistant research engineer, The Asphalt Institute, College Park, Md.

    Root, RE
    Research engineer and assistant research engineer, The Asphalt Institute, College Park, Md.


    Paper ID: STP32177S

    Committee/Subcommittee: D04.20

    DOI: 10.1520/STP32177S


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