Page 387 - Mechanics of Asphalt Microstructure and Micromechanics

Simulation of Asphalt Compaction 379

Vr Vr
Compaction layer

h T D

Different Gradation
Aggregate particle

Temperature, Stress/Strain, Force/Displacement Boundary
Conditions, and Initial Conditions.
FIGURE 11.11 Illustration of the compaction model.

Properties of the Materials
Aggregate gradation (filler percentage as well)
Maximum size of aggregate (or the dominant aggregate size) D
Aggregate shape, angularity, and texture
Asphalt content
Asphalt type and temperature sensitivity

Environmental Variables and Boundary Conditions
Mixture temperature when laid T l
Air temperature T a
Base temperature T b
Wind velocity V w
Other weather conditions (sunshine, cloudiness, humidity)
Layer thickness h
Stiffness of the lower course S
Uniformity of the above parameters

Compaction Equipment and Operation Control
Type of compactor
Rolling pattern
Number of roller passes N r
Rolling speed V r
Compaction time t

Obviously, a thorough investigation to explore how these factors affect compaction
independently or in a coupled manner would require a very complicated model or a
huge experimental factorial and tremendous costs. Identification of the critical factors
would help reduce the efforts, while still enabling solving the essential problems in
achieving effective compaction. A literature review indicates that critical factors include
layer thickness, gradation, dominant aggregate particle size (the size that constitutes
the largest percentage in the gradation), aggregate shape and angularity, temperature
(binder viscosity), base/sub-base support, and the number of passes (the compaction
system is assumed to be fixed). In addition, environmental conditions are much more