The Hale Boggs Bridge is a cable stayed bridge utilising an orthotropic steel deck. The original surfacing of the deck was an epoxy asphalt mixture. Soon after construction, the deck began to delaminate and experienced extreme shoving and permanent deformation due to non-uniform breakdown of the epoxy asphalt binder in some areas leaving the base AC-20 to perform as the binder material. This paper presents the development of a HMA mixture design to resist permanent deformation and provide extended fatigue life for the harsh environmental conditions and performance requirements experienced on the steel deck. The mix design incorporated polymer modification, SUPERPAVE performance graded binder specifications graded binder specifications and European stone mastic asphalt technology. Four specialised polymer modified asphalt binders which were requested to meet SUPERPAVE designated PG 88-22 grading were evaluated in both SMA and conventional Louisiana Type 8 mix designs. In addition, an asphalt-rubber binder modified with SBS was considered in an SMA mix design. Each mix was characterised by fundamental engineering properties including indirect tensile strength and strain at failure, creep compliance and fatigue. Overall, a Styrelf asphalt meeting SUPERPAVE PG 88-22 grading in a SMA demonstrated better laboratory performance relative to other specialised asphalt cements and conventional Type 8 wearing course combinations. (A)
Abstract