Laboratory Evaluation of Performances of Asphalt Rubber and Gap Graded Mixtures

Till now, only dry process is used to manufacture asphalt rubber (AR) in highway in China. This paper describes the production of asphalt rubber with wet process and the application of asphalt rubber for concrete pavement overlays. This paper presents: (1) selection of crumb rubber and base asphalt; (2) producing parameter tests that affect the properties of asphalt rubber; (3) evaluation of performances of asphalt rubber Stress Absorbing Membrane Interlay (AR-SAMI); (4) evaluation of different design methods of gap graded asphalt rubber mixture... After a series of tests, some conclusions were drawn from this research. Asphalt rubber using truck tire crumb rubber has better performances than that using car tire crumb. Using #20 mesh size crumb rubber can give better asphalt rubber than #40 mesh and #60 mesh crumb rubber can. As for base asphalt, asphalt rubber using penetration 70 base asphalt has better high temperature performance than that using penetration 90 base asphalt, but its low temperature performance and fatigue resistance were not as good as asphalt rubber using penetration 90 asphalt. AR-SAMI had good fatigue and shear resistance. Gap graded asphalt rubber mix designed using Superpave Gyratory Compactor(SGC) method had better rutting and low temperature cracking resistance than that using Marshall method.