Page 336 - Mechanics of Asphalt Microstructure and Micromechanics

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a. 3D Representation of Skeleton c. Triaxial Compression Test

b. 3D Representation of Void Structure d. Indirect Tensile Test

FIGURE 10.1 Illustration of the concepts of digital specimen and digital test.

of an indirect tensile test (digital test) on the same specimen. One of the advantages of
digital specimens and digital testing lies in its capability to conduct multiple tests on
the same specimen, saving different sets of equipment. Another advantage is that each
constituent can be considered as homogeneous. For example, asphalt binder can be
well modeled as a viscoelastic material, while aggregates can be modeled as elastic, so
material characterization can be more accurate.
Digital specimen and test techniques permit investigation of the strength and defor-
mation mechanisms of AC in a microscopic view that integrates mechanism identifica-
tion, numerical simulation, and experimental observations. It represents the trend for
the future mix design (Roberts et al., 2003). In addition, the generic approach to inte-
grate microstructure into modeling and simulation can be extended into other materials
such as unbound aggregates, cement concrete, and other materials with significant het-
erogeneity in material structure.

10.2 Digital Simple Performance Test of AC
Simple performance tests are used to characterize the viscoelastic, viscoplastic, and
continuum damage mechanics (CDM) material properties in pavement design. Indirect
tensile tests and dynamic modulus tests are widely used to predict the mechanical