Page 378 - Mechanics of Asphalt Microstructure and Micromechanics

370 Ch a p t e r E l ev e n

Soil Consolidation
1.9
1.8
1.7
e=1.8-0.5*logP
1.6
1.5
e
1.4
1.3
1.2
e=1.791648-0.628771*logP
1.1
1
1 1 0 1 0 0 1 0 0 0
logP
FIGURE 11.4 An analogy to soil consolidation.
consolidation stress) space. The same transformation can be performed on the asphalt
compaction curve.
As mentioned before, (A v − A v0 ) is actually the accumulative volumetric strain, and
the vertical strain in the 1D case. The term ΔA v corresponds to the incremental volumet-
ric strain or incremental vertical strain in the 1D case at the nth gyration. If the pressure
during the compaction process is kept as a constant (P), then the dissipated work (as-
suming the deformation during the compaction process is irrecoverable) on a unit vol-
ume of the sample is equal to PΔA v . Therefore, the accumulative dissipated work (dis-
sipated strain energy in terms of the material) is:
d ∑
E = N P A v (11-2)
Δ
N 0
An integral format of this formula would be:
d ∫
E = A v PdA v∫ N PK / NdN = PK Log N N ) (11-3)
l
l
(
/
A v 0 N 0 0
l
Therefore, the slope K is also a measurement of the dissipated strain energy rate
required to consolidate AC. For different mixes, such as mix A and Mix B in Figure 11.5,
the slopes are different. Many research projects have indicated that this slope is related
to the gradation, aggregate shape, angularity and texture, and asphalt binder rheology
properties (temperature dependent as well). In other words, K may be decomposed
l
into three components:
l
K = K g K m K b (11-4)
where K g = gradation contribution;
K m = aggregate morphological contribution;
K b = binder rheology contribution.

It should be noted that K m is related to aggregate shape, angularity, and texture. It is
a function of the shape, angularity, and texture factors.
While the variation of K with the above parameters as lump sum is available in many
l
laboratory testing programs, the decomposition in Equation 11-4 format is not available.