STP280

    Composition and Rheology of Roofing Asphalt

    Published: Jan 1960


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    Abstract

    A survey of twenty two roofing-grade asphalts of wide commercial distribution in the United States and Canada and derived from a number of different domestic and foreign crude oils shows that they differ widely in sulfur content, less widely in oxygen content, but are quite similar in type composition, in susceptibilities, and in softening point, penetration, and ductility.

    One of these asphalts, considered as representative, was studied with respect to its deformation response in time to low and unidirectionally applied stresses, similar to those encountered in service under forces of gravity and of thermal expansion and contraction. This asphalt behaved as a linear viscoelastic material. Its response pattern could be analyzed in terms of pure Hookean elasticity and pure Newtonian viscosity with interactions in the form of Kelvin and Maxwell compound elements. It was characterized by a high degree of damped or Kelvin elasticity, operative over a wide range of retardation or relaxation times, and a minimum of instantaneous (Hookean) elasticity and of nonrecoverable viscous (Newtonian) flow. Such rheological measures are the basic units of mechanical behavior. It is hoped that eventually they may provide solutions, in fundamental engineering terms, to problems of strength and failure in asphaltic structures.


    Author Information:

    Brown, AB
    Standard Oil Co., Whiting, Ind.

    Sparks, JW
    Standard Oil Co., Whiting, Ind.


    Paper ID: STP38450S

    Committee/Subcommittee: D08.22

    DOI: 10.1520/STP38450S


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