The details of asphalt rubber application on city streets pioneered by the city of phoenix, arizona, since the mid-1960s are outlined. Problems encountered in the early use of this material are noted.Various guidelines and specifications developed by the city for thesuccessful use of asphalt rubber are summarized. Viscosity of asphalt cement with and without an asphalt rubber seal was determined, and the importance of these results on the aging phenomenon are discussed. Many of the city's original streets with asphalt rubber application were not evaluated because they have been reconstructed. The remaining streets were inspected, and the pavement conditions for eachwere observed. Detailed observations of all the street pavements are summarized, and the important findings from this 20-year historical survey of asphalt rubber pavements are discussed. Conclusions on the use and advantages of asphalt rubber as a maintenance treatment for the city's streets are noted. In spite of the advantages and goodengineering characteristics of asphalt rubber chip seal, there was mounting public opposition to its continued use because loose chips caused damage to cars. The city therefore developed a special asphalt rubber hot mix. This alternative surface treatment has proven to be as effective and reliable as asphalt rubber chip seals. Details ofthe design of this mix and its advantages are discussed in depth. This paper appears in transportation research record no. 1307, Pavement analysis, design, rehabilitation, and environmental factors 1991.
Abstract