Purchase specifications, such as the Superpave® specification, provide a uniform set of accepted standards for purchasing asphalt and formulating mixes to suit expected road conditions. Specifications rely on tests to identify and understand characteristics that predict performance. These test methods represent specific, quantifiable contributions to the toolkits of state highway officials seeking to build better roads.
WRI develops performance-predictive tests based on research into the fundamental properties of highway materials. Our research process encompasses the following steps: 1. Identifying the variables in the chemical and physical properties of highway materials. 2. Distinguishing which properties influence performance and identifying critical performance measurements that are missing. 3. Developing models and tests. 4. Validating them using comparative pavement validation sites.
WRI delivers the tests to an Expert Task Group (ETG) made up of representatives from the FHWA and AASHTO (the American Association of State Highway Transportation Officials), asphalt producers, construction contractors and researchers.
The ETG conducts a broad-based evaluation and, if appropriate, recommends the tests to AASHTO for use by state transportation departments on a discretionary and provisional basis for a limited time. AASHTO evaluates the tests and accepts or rejects them as specifications.