Currently, the majority of the highway projects in Manitoba involve the rehabilitation of the
existing pavements. Asphalt concrete (AC) overlays with levelling, milling, cold in-place
recycling (CIR) with expanded asphalt and pulverization of the existing AC or rubblization of
existing portland cement concrete (PCC) are the common rehabilitation practices. Manitoba uses
the surface deflection based and/or the AASHTO 1993 methods for these rehabilitation designs
and is currently evaluating the new AASHTOWare Pavement ME design method. This paper
presents a comparative analysis of the required AC overlay using these three design procedures
for the above mentioned options. The suitability of the globally calibrated rutting and roughness
models and the potential for successful calibration are also discussed.
Results show that the deflection based and Pavement ME Design methods provided comparable
overlay structures for the selected projects. However, establishing a reasonable target value for
each distress in the Pavement ME is necessary for comparable overlay thicknesses. The
Pavement ME Design program under predicted the rutting for two projects with straight
overlays. However, it over predicted the rutting for these projects for the milling and overlay
option. These results are unexpected and raise the question as to whether a local calibration effort
will be effective. The CIR should be considered as an AC layer for a reasonable overlay
thickness using the Pavement ME Design program. Using the Pavement ME Design program,
the required AC thickness for the new construction is higher than that required for the
rehabilitation which is also questionable.
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