Many pavement engineers and researchers believe that the current Superpave asphalt binder specifications do not adequately predict the contribution of binder properties to asphalt mixture fatigue performance. However, at present there is not a clear alternative method to measure the fatigue performance of asphalt binders and their contribution to mixture fatigue performance. It is widely accepted that the primary factor affecting the fatigue performance of asphalt pavements is structural design: the thickness of the various layers composing the pavement system. However, other factors, including the binder content, binder aging, and the chemical and physical characteristics of the asphalt binders used in the asphalt pavement layers, can significantly affect fatigue performance. If the properties that influence binder fatigue can be identified, characterized, and specified effectively, it may be possible to specify a binder that can improve the fatigue properties of the mixture. A more effective binder specification requires one or more specification tests that do in fact relate to fatigue performance. Research is needed to develop such measures of binder fatigue properties that are indicators of asphalt mixture performance.
OBJECTIVES
The objectives of this research were to:
(1). Determine asphalt binder properties that are significant indicators of the fatigue performance of asphalt mixtures. (2). Identify or develop a practical, implementable binder test (or tests) to measure properties that are significant indicators of mixture fatigue performance for use in a performance-related binder purchase specification such as AASHTO M 320 and M 332. (3). Propose necessary changes to existing AASHTO specifications to incorporate the identified binder properties and their specification limits. (4). Validate the binder fatigue properties, test(s), and changes to existing and/or proposed AASHTO test methods and specifications with data from field projects, accelerated loading facilities, or both, supplemented, as necessary, with data from additional laboratory-prepared specimens.
