By this time of this conference, the Asphalt Research Program will have been underway for almost four years. The major asphalt research contracts have made significant strides toward understanding the relationship between asphalt's chemistry and its performance on the roadway. This paper outlines the progress to date, and presents the current understanding of the chemistry-performance link. Due to the complex and highly varied chemical makeup of paving asphalts, the relationship between asphalt chemistry and performance is difficult to state simply. In addition to its difficult chemistry, it is known that the combination of binder, aggregate, construction practices, and service environment will control the ultimate performance of the pavement. In spite of these difficulties, the SHRP researchers have made significant progress in elucidating the fundamental relationships between the composition of the asphalt binder at its ultimate performance. This progress has been accomplished through the use of an asphalt "model", a set of working hypotheses which describe the predicted behaviour of the asphalt due to its chemical constituents. Based on historical data gathered prior to the SHRP program, a "micellar" model was proposed, and used as the hypothesis upon which the experimental designs were based. Early in the research it was realized that the molecular makeup of the asphalt, rather than its detailed atomic structure, was the best key to understanding the properties of the binder. These "associations" of polar and non polar asphalt molecules have been shown to control most of the performance properties of the asphalt, although several chemical species also have an active role in performance, the details of which are the subject of this paper.
Samenvatting