Diffusion kinetics of bitumen into waste tyre rubber

Document Type

Conference Proceeding

Publication Date

12-21-2006

Abstract

Research has been conducted on the properties of paving binders modified with waste tyre rubber in the wet process. The absorption of bitumen from different sources and grades into waste truck and car-tyre rubber has been studied by weight gain experiments. Rubber monoliths cut from waste tyre threads have been immersed in hot bitumen and the increased mass of the rubber specimens at different immersion times has been used to determine the Sorption curves. The kinetics of bitumen absorption by the rubbers have been analysed in terms of the simple Fickian model, which is characteristic of absorption of solvents by rubbery polymers. Two penetration grade bitumens, 50 and 100 Pen, each from two different sources, have been used in the study. Results show that both equilibrium swelling weight increase and diffusion coefficient are related to the grade and source of the binders as well as the type of rubber. Furthermore, truck-tyre rubber absorbs more bitumen than car-tyre rubber does. Equilibrium swelling and diffusion coefficient increase when the grade of the binder used is increased, thus, when the viscosity decreases. For the same penetration grade, binders with high asphaltene content swell the rubbers markedly less and at lower rate than those with lower asphaltene content. The effect of temperature on the sorption parameters has also been investigated. Results indicate that as the temperature increases, the diffusion coefficients for the two rubbers also increase. Furthermore, the temperature dependence of the diffusion coefficient has been observed to follow an Arrhenius relationship characteristic of an activated process. It has been found that the activation energy for car-tyre rubber is greater than that of truck-tyre rubber. Moreover, diffusion coefficients determined for rubber monoliths assuming planesheet geometry have been used to estimate the kinetics of diffusion into crumb rubber particles of idealised spherical geometry.

Publication Source (Journal or Book title)

Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions

First Page

133

Last Page

164

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