Page 369 - Mechanics of Asphalt Microstructure and Micromechanics

Digital Specimen and Digital T est-Integration of Microstructure into Simulation 361

Tungsten, Gokale

Soil

Concrete Wood

FIGURE 10.46 Application of the digital specimen and digital tester techniques to
other materials.

10.6 Perspective for Digital Mix Design
Mix design for asphalt concrete is one of the most important steps in determining the
performance of constructed pavements. The principles for guiding either the Marshall
mix design method or the SuperPave mix design method are largely empirical. Al-
though empirical methods may not be eliminated due to the tremendous experience
accumulated historically, significant improvements over current mix design methods
may be made using modern tomography and computational techniques. Current mix
design methods have limitations including: 1) characteristics of the constituents (as-
phalt binder and aggregates) are not directly revealed in the mix design or linked to
performance; 2) there is a lack of mechanism on how aggregate properties such as ag-
gregate shape, angularity and texture, and binder rheology properties are compatible
with each other and contribute to the performance of mixes; 3) the mix performances
against rutting and fatigue cracking are not balanced; for example, a mix may have too
strong a resistance against rutting but not enough resistance against fatigue cracking; 4)
there is a lack of a true “performance test” to characterize the “strength” and “deforma-
tion” properties; 5) mechanisms to link lab performance with field performance cannot
be thoroughly understood due to the difficulties in developing rational models; 6) the
coupled phenomena of deformation and cracking at microscopic scale are not well ex-
plored both fundamentally and experimentally; and 7) the expenses for purchasing dif-
ferent testing equipment, training technicians, and performing tests are very high.