The selection of asphalt binder content is a key parameter for successful performance to resist both rutting and cracking. In the earliest time, binder content was selected visually. Marshall mixture design, developed in the 1940s, instituted the use of volumetric calculations. Initially the design method was based on total asphalt content and did not consider that some of the asphalt binder was absorbed into the aggregate. In 1962 the Asphalt Institute added Voids in the Mineral Aggregate as a design criterion that set the design asphalt content based on an effective volume of asphalt on the outside of the aggregate plus the amount of asphalt binder absorbed into the aggregate. The Marshall volumetric calculations were adopted into the Superpave method of design. Recently, interest in the cracking behaviour of asphalt mixtures has been increasing. Associated with this interest is the determination of how much effective asphalt binder content is in a mixture. This paper discusses the setting of asphalt binder content for mixtures, the relationship of asphalt binder parameters, and a method that can independently evaluate asphalt binder content. The role of aggregate specific gravity in volumetric calculations is highlighted. The method to evaluate asphalt binder content can be used during the mix design phase, as well as, the construction and mixture acceptance process.
展开▼
