| Potential Benefits
Donald (2003) discusses how the traditional heavy-duty pavement type is a thick asphalt
pavement placed on an unbound aggregate base and granular subbase course. This type of
conventional flexible pavement structure relies principally on the HMA for stiffness as the HMA
is the layer that provides the majority of the structural capacity. Therefore, tensile strains at the
bottom of the HMA layer need to be analyzed when designing a flexible pavement as shown in
Figure 2a. This means that the risk of fatigue cracking (flexural fatigue) that initiates at the
bottom of the HMA layer and propagates upward needs to be considered. In a composite
structure, as shown in Figure 2b, the critical strain location for flexural fatigue (tensile strain) is
shifted to a tensile stress location at the bottom of the rigid layer.
Figure 2. Shift in Critical Strain Location from a Typical Flexible Pavement (Left) to a Composite Pavement
(Right)
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