Optimum Blending Requirements for EVA Modified Binder

Abstract

Increase in traffic, new axle configurations and high temperature demands the use of modified binders for resisting the stresses induced in pavement. Ethylene Vinyl Acetate (EVA) is a plastomer, which is a copolymer obtained by copolymerization of ethylene and vinyl acetate. Though a potential modifier, problems of phase separation have been encountered attributable to the presence two separate phases of bitumen and polymer which are incompatible with each other. This paper focuses on obtaining the optimum blending requirement for EVA copolymer. A VG 10 binder was modified at varying percentages of EVA from 1 to 7%. Modification was carried out at different combination of mixing temperature, blending time and shear rate and a total of 80 combinations were obtained. Statistical package for social sciences (SPSS) and SOLVER function was used to assess the optimum blending requirement. Further the paper evaluated the optimum modifier content for obtaining a homogenous blend which could be stable at high temperature. Physical and rheological properties of the modified binder was also evaluated and compared with the base binder. It was found that temperature is the most critical parameter for EVA modification. Shear rate had the minimum influence over obtaining a storage stable blend. Fluorescence microscopy showed change in morphology as the modifier content increased, which could be used to assess the optimum modifier content for modification. Rheological response of the modified binder significantly improved. EVA modification was found to be best suited at high temperatures and could be very effective to resist rutting of mixtures.