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    Basic Rheology and Rheological Concepts Established by H. E. Schweyer

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    The flow properties of asphalts are usually characterized as Newtonian, pseudoplastic, dilatant, Bingham plastic, and thixotropic. Asphalts always exhibit some degree of elasticity. Therefore, even asphalts with Newtonian flow properties cannot be truly classified as Newtonian materials. In general, we can consider these flow categories to be a function of the shear susceptibility (complex flow) of the material. Most paving grade asphalts will exhibit Newtonian-like (C = 1.0) flow properties at or near conventional mix temperatures. At high shear rates the material may develop pronounced dilatant behavior (C > 1.0). However, at low temperature (<25°C) we often observe a greater degree of pseudoplastic (C < 1.0) behavior. The use of a fixed or specified shear rate for computation of asphalt viscosities at lower temperatures is often misleading and may result in erroneous interpretation of test results. The advantages of using constant power viscosity (ηi) is discussed in conjunction with viscosity-temperature regression analyses for evaluation of temperature susceptibility. This paper presents a thorough and concise overview of rheological types with emphasis on the need for rheological measurements throughout a range in temperature. The presentation discusses measurement methods and relies heavily on procedures purported by H. E. Schweyer as being excellent for the characterization of paving and roofing asphalts. The theoretical basis of the Schweyer constant stress rheometer is fully presented. The operation of the rheometer and procedure for analysis of data are described and illustrated by an example. The application of low-temperature viscosity test results using the Schweyer rheometer is also shown by an example.


    Schweyer rheometer, shear susceptibility, Newtonian, pseudoplastic, dilatant, Bingham plastic, thixotropic, constant power viscosity

    Author Information:

    Tia, M
    Assistant professor and professor, University of Florida, Gainesville, FL

    Ruth, BE
    Assistant professor and professor, University of Florida, Gainesville, FL

    Committee/Subcommittee: D04.44

    DOI: 10.1520/STP18525S