A New Design Framework for Flexible Long-Life Pavements

Long-life pavements are designed and built to last for over 50 years without needing

major structural rehabilitation or reconstruction. Reported benefits of such pavements include

low life-cycle cost, less frequent repair and/or rehabilitation, lower user-delay costs and lower

environmental impact. Several approaches exist to design long-life pavements, all of which are

based on mechanistic-empirical principles. While designing long-life pavements, deep structural

distresses (e.g., bottom-up cracking) are designed to never develop, by limiting the maximum

critical stresses and strains. Only surficial distresses (e.g., top-down cracking, rutting etc.) are

allowed to occur, but they are managed via periodic maintenances (e.g., mill and overlay).

Several states in the US have built long-life pavements by enhancing structural design methods,

using better materials, improving specifications and construction practices. In Michigan, four

pilot long-life pavement sections were constructed between 2017 and 2019; two rigid and two

flexible pavements. Each pilot project included a long-life and an accompanying standard

(control) section constructed on the same highway. Modifications to standard designs and

materials were made to extend their service life. The focus of this presentation is on evaluation of the two flexible pavement projects. The scope of the study included as-built analysis of these

pilot long-life projects to determine their potential for meeting the intended design and service

lives. MDOT performed numerous field tests and collected material samples from these projects.

Extensive analysis of the field data and numerous laboratory tests were conducted to characterize

the material properties. As-constructed material properties were used in different mechanistic-empirical (ME) design software to estimate the expected performance of all the pilot projects.

Based on the detailed laboratory and field testing and the mechanistic-empirical performance

predictions, recommendations were made in structural design, material selection, construction,

and quality control and quality assurance procedures. The main objective of this study was to

perform a thorough analysis of the pilot flexible long-life projects which were designed based on

state-of-the-practice methods and enhance the mechanistic-empirical design of these pavements

and propose alternative design approach for long life pavements to potentially reduce life cycle

cost and improve performance.