The pavement performance models used in the new American Association of State Highway and Transportation Officials (AASHTO) Mechanistic-Empirical Pavement Design Guide (MEPDG) were calibrated to observed field performance from the Strategic Highway Research Program (SHRP) Long Term Pavement Performance (LTPP) test sections and various other test tracks and monitoring sites throughout North America. These are considered to be “global” performance models that are generally applicable across North America. However, agencies using the MEPDG and its associated software application (DARWin-ME) are strongly encouraged to review the global models in the context of pavement performance within their jurisdictions and to undertake local validation and calibration efforts. This local calibration effort would serve to improve the transfer functions that take the MEPDG stress and strain outputs and translate them to pavement performance indicators such as slab faulting, fatigue cracking and pavement roughness. Most major highway agencies across North America are currently completing such local calibration efforts. In Canada, the Transportation Association of Canada sponsored a “roadmap” for MEPDG implementation in Canada. The coefficient of thermal expansion (CTE) is one of the critical factors considered in the design of concrete pavements. As this factor is rarely specified on Canadian projects, pavement designers typically rely on the MEPDG default values or an average value rather than project specific values. While this tended to produce “reasonable” results when using empirical pavement design procedures, the CTE has a much larger impact on the pavement design when using the much more comprehensive MEPDG procedures. DARWin-ME takes advantage of the advances in material mechanics, axle-load spectra and climate data for predicting pavement performance. Relying on the default values of CTE may lead to flawed assumptions about the pavement’s thermal response and potential distress. This paper discusses through the importance of project specific values for CTE and provides resources for reliable data. This paper also discusses the FHWA’s standard test method (adopted by AASHTO as TP60-00) for determining the CTE of concrete pavements. FHWA has been using this test method to measure CTE for over 2000 cores from across the US and was collected as part of the Long Term Pavement Performance (LTPP) program.
