Dynamic and Creep Properties of Binders Modified with Waste Tyre Rubber

Abstract

A dynamic shear rheometer was used to investigate the effect of Crumb Rubber Modifier (CRM) from used tyres on the dynamic and creep properties of bituminous binders. Modified binders were produced by blending CRM from two different origins, car and truck tyre, with bitumen under different conditions of time and temperature using a high shear mixer. Rubber-bitumen composites are considered heterogeneous (2-phase) systems of rubber particles dispersed within a bitumen matrix. Absorption of bitumen components by the rubber (swelling) inevitably depletes the bitumen of the absorbed components and modifies the properties of both the rubber and the bitumen phase. To assess the consequences, changes in dynamic properties of the composite material as well as those of the bitumen phase were investigated. Furthermore, a technique was developed to separate the two phases by filtering through a polyester cloth. Dynamic tests showed that CRM increases the stiffness and reduces the phase angle of the composite material but the extent of these changes is affected by mixing (interaction) time and temperature. They also indicated that the bitumen phase had increased stiffness and lower phase angle. The evolution of these properties with mixing time at 180 0C, however, followed the same pattern as the unmodified bitumen, which aged when heated at this temperature. Creep tests also confirmed that creep and creep recovery properties
of rubber-modified binders are affected by the origin of the rubber as well as by the mixing conditions.