Characterization of bitumens modified with SEBS, EVA and EBA polymers

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A laboratory evaluation of the modified bitumens containing styrene-ethylene-butylene-styrene (SEBS), ethylene vinyl acetate (EVA) and ethylene butyl acrylate (EBA) copolymers is presented. The morphology, storage stability and rheological and ageing properties of the modified binders were studied using fluorescence microscopy, dynamic mechanical analysis, creep test (bending beam rheometer) and conventional methods. The results indicated that the morphology and storage stability of the modified binders were largely dependent on the polymer content and were influenced by the characteristics of the base bitumens and the polymers. At a low polymer content (3% by weight), the modified binders showed dispersed polymer particles in a continuous bitumen matrix. At a sufficiently high polymer content (6% by weight), a continuous polymer phase was observed. Regardless of the nature of the two phases, the storage stability of the modified binders decreased as polymer content increased. Polymer modification improved bitumen rheological properties such as increased elastic responses at high temperatures and reduced creep stiffness at low temperatures. The degree of improvement generally increased with polymer content, but varied with bitumen source/grade and polymer type. Polymer modification also influenced bitumen ageing properties. Evaluation of ageing effect was dependent on testing conditions (e.g. temperature and frequency).

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