Field-Based Strain Thresholds for Flexible Perpetual Pavement Designs: Fid-Bau Portal

Field-Based Strain Thresholds for Flexible Perpetual Pavement Designs

Willis J. R. / Timm D. H.

Pavement engineers have been producing long-lasting hot-mix asphalt (HMA) pavements since the 1960s. Research has shown that well-constructed and adequately designed flexible pavements can perform well for extended periods of time (1). Many of these pavements in the past forty years were the products of full-depth or deep strength asphalt pavement designs, and both have design philosophies that have been shown to provide adequate strength over extended life cycles (2). Full-depth pavements are constructed by placing HMA on modified or unmodified soil or subgrade material. Deep strength pavements consist of HMA layers on top of a thin granular base. Both of these design scenarios allow pavement engineers to design thinner pavements than if a thick granular base were used. By reducing the potential for fatigue cracking and containing cracking to the upper removable/replaceable layers, many of these pavements have far exceeded their design life of 20 years with minimal rehabilitation; therefore, they are considered to be superior pavements (2). Inferior pavements are pavements that exhibit structural distresses, such as fatigue cracking and rutting (1), before their design life is achieved. The successes seen in the full-depth and deep strength pavements are the results of designing and constructing pavements that resist these detriments to the pavement’s structure. In recent years, pavement engineers have begun to introduce a methodology of designing pavements to resist the two main pavement distresses seen on roadways, and with this change in thinking has come the idea of perpetual pavements or longlasting pavements.