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Residual Bitumen Characteristics Following Dry Process Rubber-Bitumen Interaction

Authors: T.M. Singleton, G.D. Airey, I. Widyatmoko, A. Collop



The Dry Process is a method of adding recycled crumb rubber to a conventional bituminous paving mixture to impart elastomeric inclusions into the mixture. This paper describes results from a laboratory investigation of the interaction between crumb rubber and bitumen in the Dry Process. Different 100 penetration grade bitumens have been used to assess the effect of the bitumen constitution on the interaction between the rubber and bitumen. Curing tests at high temperatures have been undertaken in order to measure the amount of bitumen absorbed by the rubber during the time the mixture is held at mixing, transportation and compaction temperatures. Thin film chromatography has been used on the residual bitumen to assess the change in bitumen constituents following the interaction with the rubber. The residual bitumen samples were then tested in a Dynamic Shear Rheometer (DSR) to investigate the change in rheological properties of the bitumen due to the interaction with the crumb rubber, and in the Vialit Pendulum Cohesion Test to assess the cohesive characteristics of the residual bitumen. The results indicate that bitumen constituents have no affect on the rate of absorption of bitumen by the rubber. However, significant changes in cohesive strength and rheological properties are evident after extended periods of curing with rubber.

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