Evaluation of bitumen-rubber asphalt manufactured from modified binder at lower viscosity

Abstract

In South Africa, crumb tyre-modified bitumen commnly known as bitumen-rubber binder has viscosity limits specified by the current edition of TG1: The Use of Modified Bituminous Binders in Road Construction. As the crumb rubber is 'digested', the viscosity of the bitumen-rubber binder inevitably falls below the minimum specification, and such binder is contractually unacceptable for use. A bitumen rubber asphalt mix was manufactured using a single aggregate grading and bitumen-rubber binder specifically engineered to have a viscosity below that of the current TG1 specification. The mix was then evaluated in the laboratory using traditional Marshall design properties. The effect of change in binder viscosity on the optimum binder content was also investigated. The results obtained from this study demonstrate that further research studies are needed for low viscosity bitumen rubber and its applications in South Africa. Overall, the study provided insight into the behaviour of the low viscosity bitumen rubber for its use in road pavement construction.