27
Figure 10. Permanent Deformation (Rutting) in HMA Layer Due to the Rigidity of the Composite Pavement
Cementitious Base
Reflective Cracking Prediction
The modeling of reflective cracking was based on the study published by Sousa et al.
(2002), which proposed a mechanistic-empirical HMA overlay design
that predicts the number
of 80.2 kN (18-kip) load repetitions for a predetermined percentage of reflective cracking.
As the thickness of the HMA layer increases, the number of repetitions to achieve a 5%
reflective cracking also increases as shown in Figure 11. This mechanistic-empirical
model was
originally proposed to predict the reflected cracks on an HMA overlay placed on top of a cracked
HMA. This model was chosen to investigate reflective cracking in composite pavements
because of its practical application to predicting this type of distress on HMA overlays. In
addition, very few methodologies or procedures have been published to predict reflective
cracking on composite pavement systems (i.e., HMA on PCC or rigid bases), mainly because of
the difficulty of modeling the behavior and interface interaction of these two very different
materials. However, the findings and proposed procedure by Sousa et al. (2002), which involves
the computation of vertical crack activities before and after the overlay is placed, were assumed
to be reasonably applicable to a composite pavement system when the typical values of a
composite structure are input.
