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Abstract:
The M-EPDG represents a significant attempt to change the approach to engineering design of road structures. It reflects a shift from total reliance on empirical methods to a combination of mechanistic and empirical methods. Three instrumented road sections were used to capture the impact of local conditions. The measurements indicated that opening roads prematurely to traffic, immediately after construction, may result in high stresses and strains causing excessive deformations in both the asphaltic and unbound layers. Further, controlled truck tests confirmed the vulnerability of roads to premature and excessive distresses under low speed traffic and frequent stopping. The mechanistic characterization of road materials in the laboratory showed that the dynamic modulus is capable of capturing the effect of binder grade, temperature and frequency on the behaviour of asphaltic materials. Moreover, the findings confirmed that the resilient modulus accurately reflects the state of unbound materials in terms of moisture and density changes. The evaluation of the M-EPDG and its ability to model and predict the behaviour observed in the field showed that it is sensitive to binder performance grades as well as to climatic zones. However, the M-EPDG showed limited sensitivity to the state of unbound materials where permanent deformation showed negligible changes between wet, dry, and optimum conditions. The M-EPDG predicted rutting performances reflecting sufficient sensitivity compared to the field performance at the three different sites. The model predictions and actual field results were in good agreement and the deviations were within the margin of error. However, the M-EPDG falls short of modeling the thermal cracking which is a prevalent cause of permanent deterioration in asphalt pavements in cold regions.