No abstract

History is a dynamic tapestry of facts and perceptions, dates and personalities. This work attempts to capture the events and rationale of those who contributed significantly to the use of gyratory compaction in the design and field management of hot-mix asphalt and discusses the challenges ahead. Throughout the evolution of asphalt mix design several different types of laboratory compaction devices have been developed. In general, the goal of these laboratory devices is to fabricate a specimen for volumetric or physical characterization, or both. Depending on the system, specimens can be cylindrical, trapezoidal, or rectangular and compaction can be achieved through impact, kneading, or vibration. Gyratory compaction applies a kneading effort to fabricate cylindrical specimens. The evolution of gyratory compaction has resulted in several unique devices and a variety of methods.

The original intent of the Superpave performance tests was for the results to be input into performance models developed during the Strategic Highway Research Program that would output a prediction of various forms of pavement distress as a function of time or traffic. Unfortunately, recent research has indicated that the Superpave performance models, and some of the performance tests, have critical errors that make performance prediction impossible. Still, a substantial amount of testing has been conducted since 1994 to analyze the performance properties of asphalt mixtures. Although these data cannot be used to predict pavement performance as originally intended, the output of the Superpave performance tests can be used to calculate mechanical properties that permit relative determinations of an asphalt mixture’s stiffness and estimations of its ability to withstand permanent deformation. The objective of this study is to provide documentation of performance test results of various asphalt mixtures tested since 1994. This information is a portion of a developing database on mechanical properties of asphalt mixtures tested with the Superpave shear tester. It is intended that these values can provide guidance to the user indicating how a project’s asphalt mixture compares with other mixtures with a performance history. The study also considers the effect of changes in mixture components, sample reheating, and type of Superpave gyratory compactor on the mechanical properties of an asphalt mixture.

No abstract

A recent Federal Highway Administration survey indicated that 48 states and Puerto Rico use smoothness specifications for hot-mix asphalt (HMA) pavement construction. As this is a relatively new concept, many states have adapted the Portland cement concrete pavement specifications of Profile Index using the standard 5-mm blanking band (PI5.0) for use on HMA pavements. However, PI5.0 may not provide a reproducible or portable smoothness measure for HMA pavements because of the technical limitations of the equipment and procedures. The International Roughness Index (IRI) or the Profile Index using a 0.0-mm blanking and (PI0.0) seem to provide a more repeatable and portable smoothness standard. However, one barrier to more widespread implementation of these new smoothness standards is the lack of objective, verifiable correlation methods for use in establishing specification limits using the IRI or PI0.0. Assistance in selecting appropriate IRI and PI0.0 specification limits is needed to provide a basis for modifying current specifications to these more reproducible and portable smoothness indices. This research effort has developed a relationship between IRI and PI that can assist in transitioning to a reproducible and portable initial IRI or PI0.0 smoothness specification for HMA pavement.