Page 371 - Mechanics of Asphalt Microstructure and Micromechanics

Digital Specimen and Digital T est-Integration of Microstructure into Simulation 363

a. Step 1-Representing Individual Particles b. Step 2- Particle Packing to Form Gradation

Normal Vector
Tangent Plane
Tangent Plane at
Contact Point, O
O O 2
Branch
Connecting
Mass
O and O
1 O 1 2

c. Step 3- Determining Particle-Particle Contact for Gradation Optimization and Selection

FIGURE 10.47 Step 1 and Step 2 for digital mix design.

aggregate contacts, forming the most stable structure under various loading. This is
actually the step in parallel with selecting a gradation in the traditional mix design. Dif-
fering from the traditional approach, the selection of gradation in this method directly
utilizes the criteria for mechanical properties or performance of the mixture, such as
aggregate-aggregate contacts and local stability, etc.
Step 3: Determining the Asphalt Content
Once a gradation is selected, the voids in mineral aggregate (VMA) can be deter-
mined. For a certain air void content, such as 4%, the mastics volume, the binder vol-
ume, or the asphalt content can be determined. Compared to the traditional approach,
this method also determines the surface area of all the aggregates and therefore can