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Influence of Unbound Material Type and Input Level on Pavement Performance Using Mechanistic–Empirical Pavement Design Guide

For material characterization, the Mechanistic–Empirical Pavement Design Guide (MEPDG) has three input levels. Level 1 input values must be obtained through direct laboratory testing. Level 2 inputs are determined through correlations with other material properties. Level 3 inputs are simply typical default values. The level chosen for each design input parameter, however, may have a significant effect on project design, cost, performance, and reliability. The influence of the unbound granular base material type and material characterization input level on pavement performance, as predicted by MEPDG, was investigated for a typical flexible pavement section in climatic conditions in Egypt. Researchers analyzed seven types of virgin and recycled base materials at three weather stations representing climatic regions in Egypt: Alexandria, Cairo, and Aswan. For the typical pavement system, Level 1 data for the resilient modulus from measured laboratory values (k1, k2, and k3 elastic response coefficients) were used for the first set of MEPDG simulation runs. The second set of computer simulation runs was conducted with Level 2 data—values of the California bearing ratio—for the investigated materials. The final set of runs used default resilient modulus values for the investigated materials on the basis of the AASHTO class (Level 3). MEPDG-predicted pavement distresses and roughness for the three input levels and seven base materials were compared, and the results showed significant variation in predicted performance as a result of the change in the input level and material type.