PERFORMANCE OF CRUMB RUBBER MODIFIED BINDERS

Use of crumb rubber in asphalt mixtures can be tracked back to the 1920s. The biggest part of research work in this field has been done in the United States during the last 15 years. The US research sometimes shows contradictory results. Because of that cooperation between the pavement research centre of the University of Wuppertal and the Heiden Labor (Rostock) under sponsorship of the German Ministry of Economics has been established. During this cooperation extensive research into crumb rubber modified bitumen using recycled tires has been done. Therefor, bitumen modifications with variations of masses and sizes of crumb rubber as well as bitumen grades were tested. The property of the modified bitumen were verified with the standard tests penetration, density and softening point ring and ball as well as the performance tests bending beam rheometer, dynamic shear rheometer and force ductility. The performances of the bitumen variants show that binder properties change significantly depending on the added masses of crumb rubber (5 %, 10 % and 15 % of the bitumen) and the provenience (Russia [R] and Venezuela [V]). Softening point increase and penetration decrease for crumb rubber modified bitumen. If the softening point is plotted against the penetration for the different masses of crumb rubber nearly a linear correlation is shown. The dynamic shear rheometer tests document that there definitely is better high temperature behaviour by adding crumb rubber into bitumen. Better low temperature behaviour of crumb rubber modified bitumen show the bending beam rheometer tests. The Quantity of crumb rubber influences directly the properties of bitumen. All over it shows that conventional bitumen can be upgraded to a high-quality binder by adding crumb rubber of scrap tires (recycling material) and thus directly change and optimize different specifications (e.g. fatigue resistance, deep and high temperature behaviour, viscosity and elasticity).

PERFORMANCE OF CRUMB RUBBER MODIFIED BINDERS Keywords:

high-quality binder , crumb rubber , asphalt , bitumen performance ,