This report presents information on the effects of preservation on pavement performance and service life and describes three different approaches for considering these effects in pavement design and analysis procedures. These approaches could serve as a basis for developing procedures for incorporating preservation in the AASHTO Mechanistic-Empirical Pavement Design Guide: A Manual of Practice (MEPDG) and the AASHTOWare Pavement ME Design software. The material contained in the report will be of immediate interest to state pavement and maintenance engineers and others involved in the different aspects of pavement design and preservation. Pavement preservation provides a means for maintaining and improving the functional condition of an existing highway system and slowing deterioration. Although pavement preservation is not expected to substantially increase structural capacity, it generally leads to improved pavement performance and longer service life and, therefore, should be considered in the pavement design process. The AASHTO MEPDG and the AASHTOWare Pavement ME Design software provide methodologies for the analysis and performance prediction of different types of flexible and rigid pavements. However, these methodologies and related performance prediction models focus on new design and structural rehabilitation and do not explicitly consider the contributions of pavement preservation treatments to the overall pavement performance. Thus research was needed to identify approaches for considering the effects of preservation on pavement performance and to develop procedures that facilitate consideration of pavement preservation treatments in the MEPDG analysis process. Such procedures will ensure that the contributions of preservation to performance and service life are appropriately considered in the analysis and design process. Under NCHRP Project 1-48, “Incorporating Pavement Preservation into the MEPDG,” Applied Pavement Technology, Inc., initially worked with the objective of developing procedures for incorporating pavement preservation treatments into the MEPDG analysis process. However, as research progressed and available data associated with the performance of preservation-treated pavements were examined, it became evident that sufficient data were not available to support the development of performance-prediction models that account for these effects and would be appropriate for incorporation into the MEPDG analysis process. The research then focused on identifying and describing approaches that would serve as a basis for developing such models and illustrating how they would be incorporated in the MEPDG design and analysis procedures. To accomplish this revised objective, the researchers reviewed available information on pavement preservation and pavement design (primarily as related to the MEPDG) and interviewed representatives of selected state highway agency (SHA) and pavement industry groups to assess pavement preservation and pavement design practices and the availability of data to support the development of approaches to account for the effects of pavement preservation in pavement design and analysis procedures. Based on this work, three approaches that would allow the consideration of preservation in the MEPDG design and analysis procedures were identified. One of these approaches accounts for all aspects of structural and functional performance associated with the application of preservation treatments. Another approach builds off of the calibration/validation process outlined in the AASHTO Local Calibration Guide by collecting extensive time-series performance data from a substantive set of preservation-treated test sections to support the development of calibrated models. A third approach considers the immediate and long-term changes in materials and structure properties resulting from treatment application, although it involves a high level of complexity to accurately define these changes. These approaches are described in detail, and examples that illustrate the step-by-step process for their incorporation into the MEPDG are presented. Appendices A through I contained in the research agency’s final report provide elaborations and detail on several aspects of the research. (Author/publisher)
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