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California Division

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Superpave

Super Performing Asphalt Pavements (Superpave) were developed out of concern for numerous hot mix asphalt (HMA) pavement projects which failed after only a short time in service. Superpave was also developed specifically to address the predominant pavement distresses at that time: fatigue cracking, rutting, and thermal (transverse) cracks. After the Arab oil embargo of 1973, asphalt refiners broke ties with their traditional crude oil suppliers and began to buy from the newly developed spot market. As a consequence the refiners found a great deal of variation in the physical properties of their crude. This variability also became evident in their refined products.

Other than traditional empirical tests for asphalt binder properties (e.g. viscosity, penetration, and ductility ) asphalt consumers found themselves lacking effective mechanistic test methods to analyze and measure the performance of asphalt binders and mixes. In addition, as a result of market forces, refiners shifted their focus from asphalt to other products with higher profit margins, such as fuels and petrochemicals.

Superpave is comprised of asphalt binder technology and asphalt mixture design and analysis. Asphalt binders are graded in accordance with their performance in a standard series of stress and strain tests on original and oven-aged binders across a wide range of performance temperatures.

There are four steps to a Superpave Level One Volumetric Mix Design and analysis:

  1. Select materials - Asphalt binder is selected based on maximum and minimum service termperatures, loading rate, and traffic volumes. Aggregate is selected based on mechanical properties and gradation.
  2. Design aggregate structure is selected using control points and a restricted zone on the 0.45 power gradation chart.
  3. Design asphalt binder content is selected through HMA volumetric analysis.
  4. Moisture sensitivity of design mixes (and anti-stripping additives, if applicable) are evaluated using AASHTO T283.

A study conducted by the Texas Transportation Institute (TTI) has estimated that over $230 million will be spent for research, development and implementation of Superpave specifications over twenty years. Benefits are estimated in terms of longer lasting pavements and lower user costs due to fewer delays, accidents, and lower operating costs.

Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000